Effect of a high-protein breakfast on the postprandial ghrelin response

In vitro digestibility and angiotensin converting enzyme (ACE) inhibitory activity of solid-state fermented fava beans (Vicia faba L.)

Reducing the content of quickly absorbed carbohydrates and saturated fats in snack formulations while increasing the consumption of high-quality proteins are effective strategies to prevent obesity in childhood. Thus, the nutritional value, digestibility, and functionality of fava beans (Vicia faba L.) fermented with Pleurotus ostreatus were examined as potential ingredients for food design. Solid-state fermentation enhanced the protein content by 16% with a rise in essential (25%) and non-essential (15%) amino acids while decreasing total carbohydrate content and tannin levels. Moreover, fermentation modified the amino acid profile released during digestion, increasing amino acids such as valine, isoleucine, and threonine, which are vital for health and development in childhood. Furthermore, the bioaccessible fraction of the fermented bean showed a 60% of ACE inhibition and improved magnesium bioaccessibility. Consequently, fava beans fermented with Pleurotus ostreatus emerged as a new ingredient in the development of new protein-rich snacks tailored for children and adolescents.

Pre-prandial plasma liver-expressed antimicrobial peptide 2 (LEAP2) concentration in humans is inversely associated with hunger sensation in a ghrelin independent manner

PURPOSE

The liver-expressed antimicrobial peptide 2 (LEAP2) is a newly recognized peptide hormone that acts via the growth hormone secretagogue receptor (GHSR) blunting the effects of ghrelin and displaying ghrelin-independent actions. Since the implications of LEAP2 are beginning to be elucidated, we investigated if plasma LEAP2 concentration varies with feeding status or sex and whether it is associated with glucose metabolism and appetite sensations.

METHODS

We performed a single test meal study, in which plasma concentrations of LEAP2, ghrelin, insulin and glucose as well as visual analogue scales for hunger, desire to eat, prospective food consumption, fullness were assessed before and 60 min after breakfast in 44 participants (n = 21 females) with normal weight (NW) or overweight/obesity (OW/OB).

RESULTS

Pre-prandial plasma LEAP2 concentration was ~ 1.6-fold higher whereas ghrelin was ~ 2.0-fold lower in individuals with OW/OB (p < 0.001) independently of sex. After adjusting for body mass index (BMI) and sex, pre-prandial plasma LEAP2 concentration displayed a direct relationship with BMI (β: 0.09; 95%CI: 0.05, 0.13; p < 0.001), fat mass (β: 0.05; 95%CI: 0.01, 0.09; p = 0.010) and glycemia (β: 0.24; 95%CI: 0.05, 0.43; p = 0.021), whereas plasma ghrelin concentration displayed an inverse relationship with BMI and fat mass but not with glycemia. Postprandial plasma LEAP2 concentration increased ~ 58% in females with OW/OB (p = 0.045) but not in females with NW or in males. Pre-prandial plasma LEAP2 concentration displayed an inverse relationship with hunger score (β: - 11.16; 95% CI: - 18.52, - 3.79; p = 0.004), in a BMI-, sex- and ghrelin-independent manner.

CONCLUSIONS

LEAP2 emerges as a key hormone implicated in the regulation of metabolism and appetite in humans.

TRIAL REGISTRATION

The study was retrospectively registered in clinicaltrials.gov (April 2023).

CLINICALTRIALS

gov Identifier: NCT05815641.

Ghrelin proteolysis increases in plasma of men, but not women, with obesity

AIMS

Since plasma ghrelin can undergo des-acylation and proteolysis, the aim of this study was to investigate the extent to which an enhancement of these reactions is associated to the decrease of ghrelin in plasma after food intake or in individuals with obesity.

MAIN METHODS

we performed an intervention cross-sectional study, in which levels of ghrelin, desacyl-ghrelin (DAG), glucose, insulin, ghrelin des-acylation and ghrelin proteolysis were assessed in plasma before and after a test meal in 40 people (n = 21 males) with normal weight (NW, n = 20) or overweight/obesity (OW/OB, n = 20).

KEY FINDINGS

Preprandial ghrelin and DAG levels were lower, whereas preprandial ghrelin proteolysis was ∼4.6-fold higher in plasma of males with OW/OB. In males, ghrelin proteolysis positively correlated with glycemia. Ghrelin and DAG levels were also lower in females with OW/OB, but preprandial ghrelin proteolysis was not different between females with NW or OW/OB. Ghrelin and DAG levels decreased postprandially in males and females, independently of BMI, and ghrelin proteolysis increased postprandially ∼2 folds only in individuals with NW. Ghrelin des-acylation remained unaffected by BMI or feeding status in both sexes.

SIGNIFICANCE

Current study shows that ghrelin proteolysis increases in males with obesity as well as after meal in lean individuals. Therefore, ghrelin proteolysis may be an important checkpoint and, consequently, a putative pharmacological target to control circulating ghrelin levels in humans.

Bitter Peptides YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV, Released during Gastric Digestion of Casein, Stimulate Mechanisms of Gastric Acid Secretion via Bitter Taste Receptors TAS2R16 and TAS2R38

Eating satiating, protein-rich foods is one of the key aspects of modern diet, although a bitter off-taste often limits the application of some proteins and protein hydrolysates, especially in processed foods. Previous studies of our group demonstrated that bitter-tasting food constituents, such as caffeine, stimulate mechanisms of gastric acid secretion as a signal of gastric satiation and a key process of gastric protein digestion via activation of bitter taste receptors (TAS2Rs). Here, we tried to elucidate whether dietary non-bitter-tasting casein is intra-gastrically degraded into bitter peptides that stimulate mechanisms of gastric acid secretion in physiologically achievable concentrations. An in vitro model of gastric digestion was verified by casein-fed pigs, and the peptides resulting from gastric digestion were identified by liquid chromatography-time-of-flight-mass spectrometry. The bitterness of five selected casein-derived peptides was validated by sensory analyses and by an in vitro screening approach based on human gastric parietal cells (HGT-1). For three of these peptides (YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV), an upregulation of gene expression of TAS2R16 and TAS2R38 was observed. The functional involvement of these TAS2Rs was verified by siRNA knock-down (kd) experiments in HGT-1 cells. This resulted in a reduction of the mean proton secretion promoted by the peptides by up to 86.3 ± 9.9% for TAS2R16kd (p < 0.0001) cells and by up to 62.8 ± 7.0% for TAS2R38kd (p < 0.0001) cells compared with mock-transfected cells.

Satiety of Edible Insect-Based Food Products as a Component of Body Weight Control

Among the many aspects determining the nutritional potential of insect-based foods, research into the satiating potential of foods is an important starting point in the design of new functional foods, including those based on edible insects. The aim of this study was to assess the satiating value of products with the addition of freeze-dried insect flour. The test material included wheat pancakes in which corresponding proportions of wheat flour were substituted with 10% Mw, 0% Mw, and 30% Mw of flour from freeze-dried Tenebrio molitor, 10% Bw, 20% Bw, and 30% Bw of flour from Alphitobius diaperinus, and 10% Cr, 20% Cr, and 30% Cr of flour from Acheta domesticus. The study included the characterisation of physico-chemical properties and their effect on the satiating potential of the analysed pancakes. A total of 71 healthy volunteers (n = 39 women, n = 32 men) with no food phobias were qualified for the study. Each subject rated the level of hunger and satiety before and after ingestion at 30 min intervals over the subsequent 180 min on two separate graphical scales. The rating was done on an unstructured 100 mm visual analogue scale (VAS). A portion intended for testing had a value of 240 kcal. The highest average satiety values were noted for the pancakes with an addition of 30% Alphitobius diaperinus (Bw) and with the addition of 20% and 30% addition of Acheta domesticus flour (Cr). The Tenebrio molitor-based products were the least satiating. However, the largest addition of 30% of an insect flour for each variant considerably increased the satiating potential as compared to the control sample. Satiety was influenced the most by the protein content in the test wheat pancakes. The results support the idea of a possible usage of insect-based food products in the composition of obesity treatment diets, carbohydrate-limiting diets, and as alternative sources of protein.

Impact of food processing on postprandial glycaemic and appetite responses in healthy adults: a randomized, controlled trial

Chickpeas are among the lowest glycaemic index carbohydrate foods eliciting protracted digestion and enhanced satiety responses. In vitro studies suggest that mechanical processing of chickpeas significantly increases starch digestion. However, there is little evidence regarding the impact of processing on postprandial glycaemic response in response to chickpea intake in vivo. Therefore, the aim of this study was to determine the effect of mechanical processing on postprandial interstitial glycaemic and satiety responses in humans. In a randomised crossover design, thirteen normoglycaemic adults attended 4 separate laboratory visits following an overnight fast. On each occasion, one of four test meals, matched for available carbohydrate content and consisting of different physical forms of chickpeas (whole, puree, and pasta) or control (mashed potato), was administered followed by a subsequent standardised lunch meal. Continuous glucose monitoring captured interstitial glucose responses, accompanied by periodic venous blood samples for retrospective analysis of C-peptide, glucagon like peptide-1 (GLP-1), ghrelin, leptin, resistin, and cortisol. Subjective appetite responses were measured by Visual Analogue Scale (VAS). Postprandial glycaemic responses were comparable between chickpea treatments albeit significantly lower than the control (p < 0.001). Similarly, all chickpea treatments elicited significantly lower C-peptide and GLP-1 responses compared to the control (p < 0.05), accompanied by enhanced subjective satiety responses (p < 0.05), whilst no significant differences in satiety hormones were detected among different intervention groups (p > 0.05). Chickpea consumption elicits low postprandial glycaemic responses and enhanced subjective satiety responses irrespective of processing methods.

Prediabetes: Challenges, Novel Solutions, and Future Directions

Prediabetes: Prediabetes is a salient state of hyperglycaemia and/or hyperinsulinaemia that often precedes a diagnosis of Type 2 diabetes (T2D). It is projected that by 2040, almost 8% of the global population will have prediabetes, with approximately 70% progressing to T2D within their lifetime. Abnormal glucose tolerance increases the risk of associated complications, including cardiovascular disease, stroke, and microvascular diseases, all of which are major contributors to the global healthcare burden. T2D alone is predicted to cost the healthcare system upwards of 490 billion USD by 2030, thus addressing this growing burden is vital. Challenge One. Diagnosis and classification: Diagnosis poses a challenge and there is debate between leading world expert panels regarding thresholds, notably between the World Health Organization (WHO) and American Diabetes Association (ADA) for impaired fasting glucose. Hyperinsulinaemia may also go undetected as this is not currently routinely tested or used as diagnostic criteria. This has been largely due to cost and lack of consensus data for appropriate diagnostic threshold; however, with disease burden costs estimated to be close to half a billion USD by the end of the decade, an in-depth cost analysis for benefits-costs of early detection and treatment or prevention is warranted. Challenge Two. Health messaging and public perception: Prediabetes can revert to normoglycaemia with diet and lifestyle interventions. This, however, is not conveyed well in public health messaging. In addition to public perception about the likelihood of disease progression to T2D, prediabetes is not considered a disease state, which may also influence public perception regarding perceived urgency of treatment and necessity for intervention. Challenge Three. Intervention and treatment: Diet and lifestyle interventions are heralded as best practice when it comes to prediabetes management, and metformin for those at greatest risk of future T2D. Synergistic use of the available novel and promising interventions including low carbohydrate diets, higher protein diets, time restricted feeding, and high intensity interval training may help time-poor individuals achieve improvements in risk-factors including weight loss and glycaemic control (HbA1c and fasting plasma glucose). As large-scale feasibility and adherence are major obstacles to contend with in the rollout of diet and lifestyle interventions, personalised approaches, coupled with counselling based on social cognitive theory, may be increasingly utilised to target specific groups and individuals as programmes can be tailored to meet specific needs and preferences.

The secretion of total and acyl ghrelin from the mouse gastric mucosa: Role of nutrients and the lipid chemosensors FFAR4 and CD36

AIMS

This study investigated the nutrient-mediated modulation of total ghrelin (TG) and acyl ghrelin (AG) secretion from the mouse gastric mucosa, and the role of long-chain fatty acid chemosensors, FFAR4 and CD36, in lipid-mediated modulation of TG and AG release.

METHODS

Ex-vivo experiments were conducted using mouse gastric mucosa to examine the effects of nutrients (D-glucose, L-phenylalanine, peptone (mixture of oligopeptides & single amino acids), D-mannitol, α-linolenic acid and fat emulsion (intralipid)) on TG and AG secretion. Additionally, inhibition of FFAR4 and CD36 on α-linolenic acid and intralipid-mediated regulation of TG and AG secretion was assessed.

RESULTS

TG and AG secretion were unaffected by glucose and D-mannitol. Peptone stimulated the release of TG and AG. In contrast, L-phenylalanine reduced AG secretion only. Intralipid reduced TG secretion and stimulated AG secretion, and α-linolenic acid reduced AG release, without affecting TG mobilisation. Modulation of ghrelin secretion by lipids occurred in an FFAR4 and CD36-independent manner.

CONCLUSION

Ghrelin secretion is modulated in a nutrient-specific manner by proteins and lipids, with TG and AG displaying independent responses to the same stimuli. In addition, FFAR4 and CD36 do not participate in modulation of TG and AG secretion by α-linolenic acid and intralipid.

Protein Appetite at the Interface between Nutrient Sensing and Physiological Homeostasis

Feeding behavior is guided by multiple competing physiological needs, as animals must sense their internal nutritional state and then identify and consume foods that meet nutritional needs. Dietary protein intake is necessary to provide essential amino acids and represents a specific, distinct nutritional need. Consistent with this importance, there is a relatively strong body of literature indicating that protein intake is defended, such that animals sense the restriction of protein and adaptively alter feeding behavior to increase protein intake. Here, we argue that this matching of food consumption with physiological need requires at least two concurrent mechanisms: the first being the detection of internal nutritional need (a protein need state) and the second being the discrimination between foods with differing nutritional compositions. In this review, we outline various mechanisms that could mediate the sensing of need state and the discrimination between protein-rich and protein-poor foods. Finally, we briefly describe how the interaction of these mechanisms might allow an animal to self-select between a complex array of foods to meet nutritional needs and adaptively respond to changes in either the external environment or internal physiological state.

Both macronutrient food composition and fasting insulin resistance affect postprandial glycemic responses in senior subjects

INTRODUCTION

Postprandial hyperglycemia is a risk factor for type 2 diabetes. Insulin resistance (IR) might affect metabolic responses in non-fasting states. Dietary intake and food composition influence postprandial glucose homeostasis. The aims of this study were to evaluate the effects of different test foods varying in the macronutrient composition on postprandial glycemic responses and whether these outcomes are conditioned by the basal glycemic status in senior subjects.

METHODS

In a randomized, controlled crossover design, thirty-four adults consumed a test food, a high protein product (n = 19) or a high carbohydrate (CHO) product (n = 15), using the oral glucose tolerance test (OGTT) as a reference. Blood glucose and insulin were measured at fasting and at 15, 30, 45, 60, 90, and 120 min after starting the food intake. For each type of food, the incremental area under the curve (iAUC) for glucose and insulin was calculated. IR was measured using the Homeostatic Model Assessment of IR (HOMA-IR).

RESULTS

Consumption of a high protein product significantly lowered the peak and Δ blood glucose concentrations compared to the high CHO product (p < 0.001). Concerning the insulin response, no significant differences between both foods were observed. Fasting glucose was positively correlated with the glucose iAUC only for the high protein product. Positive associations of both fasting insulin and HOMA-IR with the insulin iAUC for all the cases were observed. Linear regression models showed significant positive associations between the glucose iAUC and fasting glucose after adjusting for age and sex. Regarding the insulin iAUC, positive associations were found with fasting insulin and HOMA-IR. Regression models also evidenced that both food test consumptions were able to decrease the glucose and insulin iAUC values when compared with the OGTT product.

CONCLUSION

Our research found that not only is the nutritional composition of foods important, but also the baseline glycemic state of individuals when assessing glycemic index estimations and addressing precision nutritional strategies to prevent and treat IR-associated disturbances.

Eggs as an affordable source of nutrients for adults and children living in food-insecure environments

Food insecurity affects an estimated 12% of households in the United States. Adults and children who experience food insecurity are increased risk for development of metabolic diseases such as type 2 diabetes, obesity, and cardiovascular disease. The negative health outcomes associated with food insecurity are multifactorial; however, many of them may be caused by limited nutritional intake and poor diet quality. Dietary intake of eggs may be an applicable solution for food-insecure families who are challenged by limited nutritional intake. Eggs contain a variety of nutrients that support metabolic health. For instance, eggs are a complete source of high-quality protein and contain 16 vitamins and minerals. Furthermore, eggs are cost efficient. When comparing the relationship between foods on the basis of calories and unit cost, the energy cost of eggs is significantly less when compared with that of other animal-protein foods such as meat, poultry, and fish. However, dietary intake of eggs is controversial in regard to cardiovascular health. Thus, the aim of this review is to summarize the role of eggs in the diet and the impact eggs have on health for adults and children living in a food-insecure environment.

Amino acids differ in their capacity to stimulate GLP-1 release from the perfused rat small intestine and stimulate secretion by different sensing mechanisms

The aim of this study was to explore individual amino acid-stimulated GLP-1 responses and the underlying stimulatory mechanisms, as well as to identify the amino acid-sensing receptors involved in amino acid-stimulated GLP-1 release. Experiments were primarily based on isolated perfused rat small intestines, which have intact epithelial polarization allowing discrimination between luminal and basolateral mechanisms as well as quantitative studies of intestinal absorption and hormone secretion. Expression analysis of amino acid sensors on isolated murine GLP-1 secreting L-cells was assessed by qPCR. We found that l-valine powerfully stimulated GLP-1 secretion but only from the luminal side (2.9-fold increase). When administered from the vascular side, l-arginine and the aromatic amino acids stimulated GLP-1 secretion equally (2.6- to 2.9-fold increases). Expression analysis revealed that Casr expression was enriched in murine GLP-1 secreting L-cells, whereas Gpr35, Gprc6a, Gpr142, Gpr93 (Lpar5), and the umami taste receptor subunits Tas1r3 and Tas1r1 were not. Consistently, activation of GPR35, GPR93, GPR142, and the umami taste receptor with specific agonists or allosteric modulators did not increase GLP-1 secretion (P > 0.05 for all experiments), whereas vascular inhibition of CaSR reduced GLP-1 secretion in response to luminal infusion of mixed amino acids. In conclusion, amino acids differ in their capacity to stimulate GLP-1 secretion. Some amino acids stimulated secretion only from the intestinal lumen, whereas other amino acids exclusively stimulated secretion from the vascular side, indicating that amino acid-stimulated GLP-1 secretion involves both apical and basolateral (postabsorptive) sensing mechanisms. Sensing of absorbed amino acids involves CaSR activation as vascular inhibition of CaSR markedly diminished amino acid stimulated GLP-1 release.NEW & NOTEWORTHY Using isolated perfused rat small intestines, we show that amino acids differ in their mechanisms and capacity of stimulating GLP-1 release. Furthermore, we demonstrate that sensing by GPR142, GPR35, GPR93, and the umami taste receptor (Tas1R1/Tas1R3) are not involved in amino acid stimulated GLP-1 release. In contrast to previous studies, this experimental model allows discrimination between the luminal and the vascular side of the intestine, which is essential when studying mechanisms of amino acid-stimulated GLP-1 secretion.

The regulation of gastric ghrelin secretion

Ghrelin is a gastric hormone with multiple physiological functions, including the stimulation of food intake and adiposity. It is well established that circulating ghrelin levels are closely associated with feeding patterns, rising strongly before a meal and lowering upon food intake. However, the mechanisms underlying the modulation of ghrelin secretion are not fully understood. The purpose of this review is to discuss current knowledge on the circadian oscillation of circulating ghrelin levels, the neural mechanisms stimulating fasting ghrelin levels and peripheral mechanisms modulating postprandial ghrelin levels. Furthermore, the therapeutic potential of targeting the ghrelin pathway is discussed in the context of the treatment of various metabolic disorders, including obesity, type 2 diabetes, diabetic gastroparesis and Prader-Willi syndrome. Moreover, eating disorders including anorexia nervosa, bulimia nervosa and binge-eating disorder are also discussed.

Effects of high-carbohydrate versus mixed-macronutrient meals on female soccer physiology and performance

PURPOSE

Athletes are often told to minimize intakes of fiber, fat, and protein in pre-competition meals to avoid gut distress, but this guidance is based on scant direct evidence. This study evaluated the physiological and perceptual effects of pre-competition mixed-macronutrient (MM) and high-carbohydrate (HCHO) meals in collegiate female soccer players.

METHODS

Fifteen players participated in this randomized, investigator-blinded, crossover study involving two ~ 1000-kcal meals (HCHO and MM) consumed 4 h prior to 70-min scrimmages. Assessments included global positioning system (GPS) tracking, heart rate (HR), perceived exertion (RPE), ratings of fatigue (ROF), gut symptoms, and perceptions of satiety, hunger, and fullness. Differences between conditions for HR, RPE, ROF, and gut symptoms were evaluated with Wilcoxon signed-rank tests. GPS data and hunger, satiety, and fullness scores were compared using within-subjects repeated measures ANOVAs.

RESULTS

No statistically significant differences were found between the conditions at any time point for HR, RPE, ROF, or gut symptoms. Significant time effects were found for two GPS variables (total distance covered and high-speed running), indicating that participants covered less distance during the second half of the scrimmages in comparison to the first half. However, there were no significant condition or condition × time interactions for GPS data. Finally, there were no condition or condition × time interactions for hunger, fullness, and satiety, though significant time effects were observed.

CONCLUSION

A MM meal consumed 4 h prior to 70 min of soccer competition does not increase gut symptoms and can be similarly ergogenic as a HCHO meal.

Effects of carbohydrate restriction on postprandial glucose metabolism, -cell function, gut hormone secretion, and satiety in patients with Type 2 diabetes

Dietary carbohydrate restriction may improve the phenotype of Type 2 diabetes (T2D) patients. We aimed to investigate 6 wk of carbohydrate restriction on postprandial glucose metabolism, pancreatic α- and β-cell function, gut hormone secretion, and satiety in T2D patients. Methods In a crossover design, 28 T2D patients (mean HbA_1c: 60 mmol/mol) were randomized to 6 wk of carbohydrate-reduced high-protein (CRHP) diet and 6 wk of conventional diabetes (CD) diet (energy-percentage carbohydrate/protein/fat: 30/30/40 vs. 50/17/33). Twenty-four-hour continuous glucose monitoring (CGM) and mixed-meal tests were undertaken and fasting intact proinsulin (IP), 32,33 split proinsulin concentrations (SP), and postprandial insulin secretion rates (ISR), insulinogenic index (IGI), β-cell sensitivity to glucose (B_up), glucagon, and gut hormones were measured. Gastric emptying was evaluated by postprandial paracetamol concentrations and satiety by visual analog scale ratings. A CRHP diet reduced postprandial glucose area under curve (net AUC) by 60% (P < 0.001), 24 h glucose by 13% (P < 0.001), fasting IP and SP concentrations (both absolute and relative to C-peptide, P < 0.05), and postprandial ISR (24%, P = 0.015), while IGI and B_up improved by 31% and 45% (both P < 0.001). The CRHP diet increased postprandial glucagon net AUC by 235% (P < 0.001), subjective satiety by 18% (P = 0.03), delayed gastric emptying by 15 min (P < 0.001), decreased gastric inhibitory polypeptide net AUC by 29% (P < 0.001), but had no significant effect on glucagon-like-peptide-1, total peptide YY, and cholecystokinin responses. A CRHP diet reduced glucose excursions and improved β-cell function, including proinsulin processing, and increased subjective satiety in patients with T2D.

Physical properties, sensory acceptance, postprandial glycemic response, and satiety of cereal based foods enriched with legume flours: a review

Legumes are rich in proteins and widely consumed around the world. Their consumption has been associated with improved glycemic and lipidemic profile and positive alterations of gut microbiota. These beneficial effects have created a growing scientific interest in the role of legume-enriched foods on the promotion of human health. The aim of this review was to critically record the studies examining the nutritional value and textural properties of these products, as well as their efficacy on lowering postprandial glucose response and satiety. Reviewed data have shown that cereal products with high nutritional value are formulated when fortified with legume flours. The postprandial glucose response appears to be ameliorated and the enriched foods have a medium or a low glycemic index, however not enough data are presented referring to the appetite hormones responses. Textural properties are affected by the addition of legumes and occasionally, when substitution level is high, the final product has not acceptable odor and appearance. To overcome this barrier, particular food processes such as fermentation, extrusion and addition of hydrocolloids, are used and have shown great results on the textural and sensory properties of the final products. The development of healthy legume-enriched cereal-based products is of great importance for the increase of legume consumption and the promotion of public health.

Appetite Control across the Lifecourse: The Acute Impact of Breakfast Drink Quantity and Protein Content. The Full4Health Project

Understanding the mechanisms of hunger, satiety and how nutrients affect appetite control is important for successful weight management across the lifecourse. The primary aim of this study was to describe acute appetite control across the lifecourse, comparing age groups (children, adolescents, adults, elderly), weight categories, genders and European sites (Scotland and Greece). Participants (n = 391) consumed four test drinks, varying in composition (15% (normal protein, NP) and 30% (high protein, HP) of energy from protein) and quantity (based on 100% basal metabolic rate (BMR) and 140% BMR), on four separate days in a double-blind randomized controlled study. Ad libitum energy intake (EI), subjective appetite and biomarkers of appetite and metabolism (adults and elderly only) were measured. The adults' appetite was significantly greater than that of the elderly across all drink types (p < 0.004) and in response to drink quantities (p < 0.001). There were no significant differences in EI between age groups, weight categories, genders or sites. Concentrations of glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) were significantly greater in the elderly than the adults (p < 0.001). Ghrelin and fasting leptin concentrations differed significantly between weight categories, genders and sites (p < 0.05), while GLP-1 and PYY concentrations differed significantly between genders only (p < 0.05). Compared to NP drinks, HP drinks significantly increased postprandial GLP-1 and PYY (p < 0.001). Advanced age was concomitant with reduced appetite and elevated anorectic hormone release, which may contribute to the development of malnutrition. In addition, appetite hormone concentrations differed between weight categories, genders and geographical locations.

The Association of Serum Levels of Leptin and Ghrelin with the Dietary Fat Content in Non-Obese Women with Polycystic Ovary Syndrome

Women with polycystic ovary syndrome (PCOS) are at an increased risk of developing insulin resistance and abdominal obesity in the state of an improper diet balance. Leptin is a peptide considered to be a satiety hormone that plays an important role in the long-term energy balance, whereas ghrelin is a hormone that controls short-term appetite regulation and is considered a hunger hormone. The aim of the present study was to assess the relationship between serum leptin and ghrelin concentrations and the dietary macronutrient content in PCOS women. We examined 73 subjects: 39 women diagnosed with PCOS by the Rotterdam criteria and 34 healthy controls, matched by the body mass index. The subjects completed a consecutive three-day dietary diary to identify the macronutrient and micronutrient intake. Serum concentrations of leptin and total ghrelin were measured and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. The studied groups did not differ significantly in terms of the intake of macronutrients (proteins, fats, and carbohydrates) and serum concentrations of ghrelin and leptin (all p > 0.05). In the PCOS group, the serum leptin concentration positively correlated with the intake of total fat (r = 0.36, p = 0.02), total cholesterol (r = −0.36, p = 0.02), saturated fatty acids (r = 0.43, p < 0.01), and monounsaturated fatty acids (MUFA) (r = 0.37, p = 0.02), whereas the serum ghrelin concentration correlated in an inverse manner with the intake of total fat (r = −0.37, p = 0.02), MUFA (r = −0.37, p = 0.02), polyunsaturated fatty acids (r = −0.34, p = 0.03), and long chain polyunsaturated fatty acids (r = −0.38, p = 0.02). In this group, we also found a negative association of HOMA-IR with serum ghrelin levels (r = −0.4, p = 0.03) and a positive relationship with the serum leptin concentration (r = 0.5, p < 0.01) and relationships between HOMA-IR and total dietary fat (r = 0.38, p = 0.03) and MUFA (r = 0.35, p = 0.04) intake. In PCOS women, dietary components such as the total fat and type of dietary fat and HOMA-IR are positively connected to serum leptin concentrations and negatively connected to serum ghrelin concentrations, which may influence the energy balance.

Does high dietary protein intake contribute to the increased risk of developing prediabetes and type 2 diabetes?

Insulin resistance is a complex metabolic disorder implicated in the development of many chronic diseases. While it is generally accepted that body mass loss should be the primary approach for the management of insulin resistance-related disorders in overweight and obese individuals, there is no consensus among researchers regarding optimal protein intake during dietary restriction. Recently, it has been suggested that increased plasma branched-chain amino acids concentrations are associated with the development of insulin resistance and type 2 diabetes. The exact mechanism by which excessive amino acid availability may contribute to insulin resistance has not been fully investigated. However, it has been hypothesised that mammalian target of rapamycin (mTOR) complex 1 hyperactivation in the presence of amino acid overload contributes to reduced insulin-stimulated glucose uptake because of insulin receptor substrate (IRS) degradation and reduced Akt-AS160 activity. In addition, the long-term effects of high-protein diets on insulin sensitivity during both weight-stable and weight-loss conditions require more research. This review focusses on the effects of high-protein diets on insulin sensitivity and discusses the potential mechanisms by which dietary amino acids can affect insulin signalling. Novelty: Excess amino acids may over-activate mTOR, resulting in desensitisation of IRS-1 and reduced insulin-mediated glucose uptake.

Effects of Age on Acute Appetite-Related Responses to Whey-Protein Drinks, Including Energy Intake, Gastric Emptying, Blood Glucose, and Plasma Gut Hormone Concentrations-A Randomized Controlled Trial

Protein-rich supplements are used commonly to increase energy intake in undernourished older people. This study aimed to establish age effects on energy intake, appetite, gastric emptying, blood glucose, and gut hormones in response to protein-rich drinks. In a randomized double-blind, order, 13 older men (age: 75 ± 2 yrs, body mass index (BMI): 26 ± 1 kg/m²) and 13 younger (23 ± 1 yrs, 24 ± 1 kg/m²) men consumed (i) a control drink (~2 kcal) or drinks (450 mL) containing protein/fat/carbohydrate: (ii) 70 g/0 g/0 g (280 kcal/'P_280'), (iii) 14 g/12.4 g/28 g (280 kcal/'M_280'), (iv) 70 g/12.4 g/28 g (504 kcal/'M_504'), on four separate days. Appetite (visual analog scales), gastric emptying (3D ultrasonography), blood glucose, plasma insulin, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) concentrations (0-180 min), and ad-libitum energy intake (180-210 min) were determined. Older men, compared to younger men, had higher fasting glucose and CCK concentrations and lower fasting GLP-1 concentrations (all p < 0.05). Energy intake by P₂₈₀ compared to control was less suppressed in older men (increase: 49 ± 42 kcal) than it was in younger men (suppression: 100 ± 54 kcal, p = 0.038). After the caloric drinks, the suppression of hunger and the desire to eat, and the stimulation of fullness was less (p < 0.05), and the stimulation of plasma GLP-1 was higher (p < 0.05) in older men compared to younger men. Gastric emptying, glucose, insulin, ghrelin, and CCK responses were similar between age groups. In conclusion, ageing reduces the responses of caloric drinks on hunger, the desire to eat, fullness, and energy intake, and protein-rich nutrition supplements may be an effective strategy to increase energy intake in undernourished older people.

Effect of Plain Versus Sugar-Sweetened Breakfast on Energy Balance and Metabolic Health: A Randomized Crossover Trial

OBJECTIVE

This study investigated the effect of 3 weeks of high-sugar ("Sweet") versus low-sugar ("Plain") breakfast on energy balance, metabolic health, and appetite.

METHODS

A total of 29 healthy adults (22 women) completed this randomized crossover study. Participants had pre- and postintervention appetite, health, and body mass outcomes measured, and they recorded diet, appetite (visual analogue scales), and physical activity for 8 days during each intervention. Interventions were 3 weeks of isoenergetic Sweet (30% by weight added sugar; average 32 g of sugar) versus Plain (no added sugar; average 8 g of sugar) porridge-based breakfasts.

RESULTS

Pre- to postintervention changes in body mass were similar between Plain (Δ 0.1 kg; 95% CI: -0.3 to 0.5 kg) and Sweet (Δ 0.2 kg; 95% CI: -0.2 to 0.5 kg), as were pre- to postintervention changes for biomarkers of health (all P ≥ 0.101) and psychological appetite (all P ≥ 0.152). Energy, fat, and protein intake was not statistically different between conditions. Total carbohydrate intake was higher during Sweet (287 ± 82 g/d vs. 256 ± 73 g/d; P = 0.009), driven more by higher sugar intake at breakfast (116 ± 46 g/d vs. 88 ± 38 g/d; P < 0.001) than post-breakfast sugar intake (Sweet 84 ± 42 g/d vs. Plain 80 ± 37 g/d; P = 0.552). Participants reported reduced sweet desire immediately after Sweet but not Plain breakfasts (trial × time P < 0.001).

CONCLUSIONS

Energy balance, health markers, and appetite did not respond differently to 3 weeks of high- or low-sugar breakfasts.

Acute effect of a cod protein hydrolysate on postprandial acylated ghrelin concentration and sensations associated with appetite in healthy subjects: a double-blind crossover trial

Background

Fish protein hydrolysates are suggested to contain bioactive sequences capable of affecting metabolic pathways involved in the regulation of glucose metabolism and body weight when consumed in low doses. Modulation of the appetite-regulating hormone ghrelin may explain suppression of insulin secretion and weight loss observed in previous studies with fish protein hydrolysates.

Objective

This study aimed to assess the effect of a single, low dose of cod protein hydrolysate (CPH) before a breakfast meal on postprandial acylated ghrelin concentration and sensations associated with appetite in healthy subjects.

Design

In this explorative trial with a crossover design, 41 healthy individuals (15 males and 26 females, age 51 ± 6 years) completed 2 study days separated by 4–7 days of washout. On both study days, a test drink containing 20 mg CPH or casein (control) per kg body weight was given immediately before a standardized breakfast meal. Acylated ghrelin concentrations were measured before test drink/breakfast (baseline) and at time 0, 20, 40, 80, and 180 min postprandially. Sensations associated with appetite were measured by a Visual Analog Scale (100 mm) at baseline and 0, 20, 40, and 180 min postprandially.

Results

Statistically, no difference was observed between CPH and control for postprandial acylated ghrelin concentrations (mean difference geometric mean: 1.05 pg/mL, 95% confidence interval [CI]: 0.97–1.13, P = 0.266), or between the total area under the curve (tAUC) for acylated ghrelin after CPH (tAUC = 17518 pg/mL × min, 95% CI: 0–47941) and control (tAUC = 17272 pg/mL × min, 95% CI: 0–48048, P = 0.991). No differences were found between CPH and control for sensation of appetite, according to tAUC of postprandial scores for satiety (P = 0.794) and the feeling of fullness (P = 0.996).

Conclusion

We did not find an effect of a single dose of CPH on postprandial concentrations of acylated ghrelin or sensations related to feeling of hunger, compared to control. Further studies should aim to evaluate the effect of a supplement with CPH given daily over a period of time.

Simple techniques to study multifaceted diabesity in the fly model

Diabetes and obesity are the two notorious metabolic disorders in today's world. Both diabetes and obesity are interlinked with each other and often referred to as 'Diabesity'. It is a complex and multi-organ failure disorder. Thus, many researches and tremendous efforts have been made toward prevention, treatment as well as early detection of diabesity. However, and still, there is a large gap in understanding the etiology as well as treatment of diabesity. Various animal models are also used to decipher the mechanism underlying diabesity. Among all the model organism, recently Drosophila melanogaster is gaining its importance to study diabetes, obesity, and other metabolic disorder. Various experimental methods like histological, biochemical, developmental, and behavioral assays are described in this study to detect diabetes as well as obesity in the fly model.

How Satiating Are the 'Satiety' Peptides: A Problem of Pharmacology versus Physiology in the Development of Novel Foods for Regulation of Food Intake

Developing novel foods to suppress energy intake and promote negative energy balance and weight loss has been a long-term but commonly unsuccessful challenge. Targeting regulation of appetite is of interest to public health researchers and industry in the quest to develop ‘functional’ foods, but poor understanding of the underpinning mechanisms regulating food intake has hampered progress. The gastrointestinal (GI) or ‘satiety’ peptides including cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) secreted following a meal, have long been purported as predictive biomarkers of appetite response, including food intake. Whilst peptide infusion drives a clear change in hunger/fullness and eating behaviour, inducing GI-peptide secretion through diet may not, possibly due to modest effects of single meals on peptide levels. We conducted a review of 70 dietary preload (DIET) and peptide infusion (INFUSION) studies in lean healthy adults that reported outcomes of CCK, GLP-1 and PYY. DIET studies were acute preload interventions. INFUSION studies showed that minimum increase required to suppress ad libitum energy intake for CCK, GLP-1 and PYY was 3.6-, 4.0- and 3.1-fold, respectively, achieved through DIET in only 29%, 0% and 8% of interventions. Whether circulating ‘thresholds’ of peptide concentration likely required for behavioural change can be achieved through diet is questionable. As yet, no individual or group of peptides can be measured in blood to reliably predict feelings of hunger and food intake. Developing foods that successfully target enhanced secretion of GI-origin ‘satiety’ peptides for weight loss remains a significant challenge.

Satiating Effect of High Protein Diets on Resistance-Trained Subjects in Energy Deficit

Short-term energy deficit strategies are practiced by weight class and physique athletes, often involving high protein intakes to maximize satiety and maintain lean mass despite a paucity of research. This study compared the satiating effect of two protein diets on resistance-trained individuals during short-term energy deficit. Following ethical approval, 16 participants (age: 28 ± 2 years; height: 1.72 ± 0.03 m; body-mass: 88.83 ± 5.54 kg; body-fat: 21.85 ± 1.82%) were randomly assigned to 7-days moderate (PRO_MOD: 1.8 g·kg^-1·d^-1) or high protein (PRO_HIGH: 2.9 g·kg^-1·d^-1) matched calorie-deficit diets in a cross-over design. Daily satiety responses were recorded throughout interventions. Pre-post diet, plasma ghrelin and peptide tyrosine tyrosine (PYY), and satiety ratings were assessed in response to a protein-rich meal. Only perceived satisfaction was significantly greater following PRO_HIGH (67.29 ± 4.28 v 58.96 ± 4.51 mm, p = 0.04). Perceived cravings increased following PRO_MOD only (46.25 ± 4.96 to 57.60 ± 4.41 mm, p = 0.01). Absolute ghrelin concentration significantly reduced post-meal following PRO_MOD (972.8 ± 130.4 to 613.6 ± 114.3 pg·mL^-1; p = 0.003), remaining lower than PRO_HIGH at 2 h (-0.40 ± 0.06 v -0.26 ± 0.06 pg·mL^-1 normalized relative change; p = 0.015). Absolute PYY concentration increased to a similar extent post-meal (PRO_MOD: 84.9 ± 8.9 to 147.1 ± 11.9 pg·mL^-1, PRO_HIGH: 100.6 ± 9.5 to 143.3 ± 12.0 pg·mL^-1; p < 0.001), but expressed as relative change difference was significantly greater for PRO_MOD at 2 h (+0.39 ± 0.20 pg·mL^-1 v -0.28 ± 0.12 pg·mL^-1; p = 0.001). Perceived hunger, fullness and satisfaction post-meal were comparable between diets (p > 0.05). However, desire to eat remained significantly blunted for PRO_MOD (p = 0.048). PRO_HIGH does not confer additional satiating benefits in resistance-trained individuals during short-term energy deficit. Ghrelin and PYY responses to a test-meal support the contention that satiety was maintained following PRO_MOD, although athletes experiencing negative symptoms (i.e., cravings) may benefit from protein-rich meals as opposed to over-consumption of protein.

The effect of breakfast with different macronutrient composition on PYY, ghrelin, and ad libitum intake 4 h after breakfast in Indonesian obese women

OBJECTIVES

Gut hormones, such as PYY and ghrelin, are associated with appetite control and obesity. Protein is thought to be the most satiating nutrient and could affect the production of several gut hormones. The purpose of the current study was to find the effect of breakfast with different protein composition on PYY, ghrelin, and ad libitum intake 4 h after breakfast.

RESULTS

This clinical trial involves 22 obese women participants. Subjects were given three types of breakfast: low protein consumption (12.4% protein), medium protein (23.5% protein), and high protein (40.6% protein). PYY and ghrelin levels were measured at 0, 15, 60, 120, and 180 min after breakfast. Ad libitum meal was given 4 h after breakfast and measured after. This study found that there is no significant difference in PYY and ghrelin level at each measurement time between different type of breakfast. This study also found no significant difference of ad libitum energy intake between different type of breakfast. Trial registration ClinicalTrials.gov NCT03697486, 3 December 2018. Retrospectively registered.

Acute Effects of Substitution, and Addition, of Carbohydrates and Fat to Protein on Gastric Emptying, Blood Glucose, Gut Hormones, Appetite, and Energy Intake

Whey protein, when ingested on its own, load-dependently slows gastric emptying and stimulates gut hormone concentrations in healthy young men. The aim of this study was to determine the effects of substitution, and addition, of carbohydrate (dextrose) and fat (olive oil) to whey protein. In randomized, double-blind order, 13 healthy young men (age: 23 ± 1 years, body mass index: 24 ± 1 kg/m²) ingested a control drink (450 mL; ~2 kcal/'control') or iso-volumetric drinks containing protein/carbohydrate/fat: (i) 14 g/28 g/12.4 g (280 kcal/'M_280'), (ii) 70 g/28 g/12.4 g (504kcal/'M_504'), and (iii) 70 g/0 g/0 g (280 kcal/'P_280'), on 4 separate study days. Gastric emptying (n = 11, 3D-ultrasonography), blood glucose, plasma insulin, ghrelin, cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) concentrations (0⁻180 min), appetite (visual analogue scales), and ad-libitum buffet-meal energy intake (180⁻210 min) were determined. Substitution of protein with carbohydrate and fat was associated with faster gastric emptying (lower 50% emptying time (T50)), reduced suppression of ghrelin, and stimulation of GLP-1 (all P < 0.001); while the addition of carbohydrate and fat to protein did not affect gastric emptying or gut hormone responses significantly. Total energy intake (i.e., drink plus meal) was greater after all caloric drinks than control (P < 0.001). In conclusion, substitution of whey protein with dextrose and olive oil accelerated gastric emptying. Higher protein content of a mixed macronutrient drink increased gut hormone and insulin responses.

Breakfast Consumption in the UK: Patterns, Nutrient Intake and Diet Quality. A Study from the International Breakfast Research Initiative Group

Breakfast consumption is associated with higher overall dietary adequacy; however, there is a lack of quantitative guidelines for optimal nutrient intakes at breakfast in the UK. This study aimed to investigate nutrient and food group intakes at breakfast and examine their relationship to overall Diet Quality (DQ). Data from the most recent National Diet and Nutrition Survey (NDNS, 2008⁻2014) were accessed to provide a representative sample (n = 8174) of the UK population, aged 5⁻96 years, mean age of 33 years. Food intake was measured by a 4-day estimated food diary and DQ was assessed by the Nutrient Rich Food Index 9.3 method. Energy- and socio-economic-adjusted nutrient and food group intakes were compared across age groups and DQ tertiles by ANCOVA. Breakfast contributed 20⁻22% to total energy intake. Breakfast intakes of carbohydrate and non-milk extrinsic sugars (NMES) were higher, and intakes of protein, total fat and saturated fatty acid (SFA) were lower, than relative daily intakes. Breakfast was particularly rich in B vitamins, vitamin D, calcium, iron, iodine and magnesium. From the lowest to the highest DQ tertile decreasing intakes of NMES, SFA and total fat and increasing intakes of carbohydrate, protein, fibre and most micronutrients were found. These findings could help to inform the development of nutrient-based recommendations for a balanced breakfast for the first time in the UK.

Subjective feelings of appetite of wholegrain breakfasts evaluated under controlled, laboratory and 'at home' conditions

BACKGROUND

Appetite regulating properties of foods are usually investigated under laboratory conditions, whereas in real life, foods are consumed under at home conditions. The objective of this study was to compare the acute effects of breakfasts when tested in a laboratory condition and in an at home condition. Appetite regulating properties of two bread breakfasts and two cereal breakfasts were also compared.

SUBJECTS AND METHODS

In this randomized cross-over trial balanced for laboratory and at home test conditions, thirty-two women consumed five breakfasts, i.e. two bread breakfasts, two cereal breakfasts and one fried-egg breakfast. Visual analogue scales for measuring appetite were captured via an on-line scoring system and were analyzed as incremental area under the curve, as satiation phase and as satiety phase.

RESULTS

Location effects were limited to two small effects only. An overall location effect in hunger feelings was observed (p = 0.040), which occurred specifically during the short satiation period (p = 0.0002) where hunger feelings scored higher under laboratory conditions. Similarly, a location effect was observed for desire to eat (p = 0.001); this was again higher under laboratory conditions. No other location effects were observed. Bread breakfasts did not differ in their appetite regulating properties. The Steel Cut oatmeal breakfast was reported to be more satiating (p = 0.001) as compared to the ready-to-eat cereal.

CONCLUSIONS

Whereas the five breakfasts varied somewhat in their appetite regulating properties, evaluation under laboratory conditions overall did not result in different appetite scores compared to the at home conditions. This suggests that at home testing may be a useful alternative to laboratory test conditions for nutrition research.

The effects of added whey protein to a pre-operative carbohydrate drink on glucose and insulin response

BACKGROUND

Pre-operative complex carbohydrate (CHO) drinks are recommended to attenuate post-operative insulin resistance. However, many institutions use simple CHO drinks, which while convenient, may have less metabolic effects. Whey protein may enhance insulin release when added to complex CHO. The aim of this study was to compare the insulin response to simple CHO vs. simple CHO supplemented with whey protein.

METHODS

Twelve healthy volunteers participated in this double-blinded, within subject, cross-over design study investigating insulin response to simple CHO drink vs. simple CHO + whey (CHO + W) drink. The primary outcome was the accumulated insulin response during 180 min after ingestion of the drinks (Area under the curve, AUC). Secondary outcomes included plasma glucose and ghrelin levels, and gastric emptying rate estimated by acetaminophen absorption technique. Data presented as mean (SD).

RESULTS

There was no differences in accumulated insulin response after the CHO or CHO + W drinks [AUC: 15 (8) vs. 20 (14) nmol/l, P = 0.27]. Insulin and glucose levels peaked between 30 and 60 min and reached 215 (95) pmol/l and 7 (1) mmol/l after the CHO drink and to 264 (232) pmol/l and 6.5 (1) mmol/l after the CHO + W drink. There were no differences in glucose or ghrelin levels or gastric emptying with the addition of whey.

CONCLUSION

The addition of whey protein to a simple CHO drink did not change the insulin response in healthy individuals. The peak insulin responses to simple CHO with or without whey protein were lower than that previously reported with complex CHO drinks. The impact of simple carbohydrate drinks with lower insulin response on peri-operative insulin sensitivity requires further study.

Effects of Substitution, and Adding of Carbohydrate and Fat to Whey-Protein on Energy Intake, Appetite, Gastric Emptying, Glucose, Insulin, Ghrelin, CCK and GLP-1 in Healthy Older Men-A Randomized Controlled Trial

Protein-rich supplements are used widely for the management of malnutrition in the elderly. We reported previously that the suppression of energy intake by whey protein is less in older than younger adults. The aim was to determine the effects of substitution, and adding of carbohydrate and fat to whey protein, on ad libitum energy intake from a buffet meal (180-210 min), gastric emptying (3D-ultrasonography), plasma gut hormone concentrations (0-180 min) and appetite (visual analogue scales), in healthy older men. In a randomized, double-blind order, 13 older men (75 ± 2 years) ingested drinks (~450 mL) containing: (i) 70 g whey protein (280 kcal; 'P₂₈₀'); (ii) 14 g protein, 28 g carbohydrate, 12.4 g fat (280 kcal; 'M₂₈₀'); (iii) 70 g protein, 28 g carbohydrate, 12.4 g fat (504 kcal; 'M₅₀₄'); or (iv) control (~2 kcal). The caloric drinks, compared to a control, did not suppress appetite or energy intake; there was an increase in total energy intake (drink + meal, p < 0.05), which was increased most by the M₅₀₄-drink. P₂₈₀- and M₅₀₄-drink ingestion were associated with slower a gastric-emptying time (n = 9), lower ghrelin, and higher cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) than M₂₈₀ (p < 0.05). Glucose and insulin were increased most by the mixed-macronutrient drinks (p < 0.05). In conclusion, energy intake was not suppressed, compared to a control, and particularly whey protein, affected gastric emptying and gut hormone responses.

Increased Protein Consumption during the Day from an Energy-Restricted Diet Augments Satiety but Does Not Reduce Daily Fat or Carbohydrate Intake on a Free-Living Test Day in Overweight Women

Background: Higher-protein (HP) energy-restriction diets improve weight management to a greater extent than normal-protein (NP) versions. Potential mechanisms of action with regard to assessment of eating behaviors across the day have not been widely examined during energy restriction.Objectives: The objectives of this study were to test whether the consumption of an HP energy-restriction diet reduces carbohydrate and fat intakes through improvements in daily appetite, satiety, and food cravings compared with NP versions and to test whether protein type within the NP diets alters protein-related satiety.Methods: Seventeen overweight women [mean ± SEM age: 36 ± 1 y; body mass index (kg/m²): 28.4 ± 0.1] completed a randomized, controlled-feeding crossover study. Participants were provided with the following ∼1250-kcal/d energy-restricted (-750-kcal/d deficit) diets, each for 6 d: HP [124 g protein/d; 60% from beef and 40% from plant sources (HP-BEEF)] or NP (48 g protein/d) that was protein-type matched (NP-BEEF) or unmatched [100% from plant-based sources (NP-PLANT)]. On day 6 of each diet period, participants completed a 12-h testing day containing repetitive appetite, satiety, and food-craving questionnaires. On day 7, the participants were asked to consume their protein requirement within each respective diet but were provided with a surplus of carbohydrate- and fat-rich foods to consume, ad libitum, at each eating occasion across the day. All outcomes reported were primary study outcomes.Results: The HP-BEEF diet reduced daily hunger by 16%, desire to eat by 15%, prospective food consumption by 14%, and fast-food cravings by 15% but increased daily fullness by 25% compared with the NP-BEEF and NP-PLANT diets (all P < 0.05). However, consuming more protein throughout the day did not reduce the energy consumed ad libitum from the fat- and carbohydrate-rich foods (HP-BEEF: 2000 ± 180 kcal/d; NP-BEEF: 2120 ± 190 kcal/d; NP-PLANT: 2070 ± 180 kcal/d). None of the outcomes differed between the NP-BEEF and NP-PLANT treatments.Conclusions: Although appetite control, satiety, and food cravings improved after an HP energy-restriction diet, increased protein consumption did not reduce carbohydrate and fat intakes throughout the free-living test day in overweight healthy women exposed to highly palatable foods. This trial was registered at clinicaltrials.gov as NCT02614729.

Appetite and Gut Hormones Response to a Putative α-Glucosidase Inhibitor, Salacia Chinensis, in Overweight/Obese Adults: A Double Blind Randomized Controlled Trial

Animal studies indicate Salacia reduces body weight, possibly due to its α-glucosidase inhibitor (α-GI) properties, but this has not been examined previously. In this study, a randomized, placebo-controlled, three-way cross-over design was used to evaluate whether Salacia Chinensis (SC) reduces appetite in healthy overweight/obese individuals (body mass index 28.8 ±3.6 kg/m²; 32 ± 12 years). Forty-eight participants were fasted overnight and consumed a dose of SC (300 or 500 mg) or placebo with a fixed breakfast meal at each visit. Appetite sensations, glycemic indices and gastrointestinal peptides were measured. Results indicated that SC had no effect on postprandial appetite. However, in women, hunger was reduced by SC compared to placebo at multiple time points (300 mg; p < 0.05), but not in men. Area under the curve (AUC) for serum glucose, insulin and amylin was attenuated with SC compared to placebo (p < 0.05). Glucagon like peptide-1 had two peaks after the meal, but the AUC did not differ between groups. The AUC of peak areas for peptide YY and ghrelin were greater for SC than placebo (p < 0.05). These findings indicate that Salacia decreases glycemic indices supporting its role as an α-GI, and affects certain gastrointestinal peptides suggesting it may be an appetite modulator.

High-energy breakfast based on whey protein reduces body weight, postprandial glycemia and HbA1C in Type 2 diabetes

Acute studies show that addition of whey protein at breakfast has a glucose-lowering effect through increased incretin and insulin secretion. However, whether this is a long-term effect in Type 2 diabetes is unknown. Fifty-six Type 2 diabetes participants aged 58.9±4.5 years, BMI 32.1±0.9 kg/m² and HbA_1C 7.8±0.1% (61.6±0.79 mmol/mol) were randomized to one of 3 isocaloric diets with similar lunch and dinner, but different breakfast: 1) 42 g total protein, 28 g whey (WBdiet, n=19); 2) 42 g various protein sources (PBdiet, n=19); or 3) high-carbohydrate breakfast, 17 g protein from various sources (CBdiet, n=18). Body weight and HbA_1C were examined after 12 weeks. All participants underwent three all-day meal challenges for postprandial glycemia, insulin, C-peptide, intact glucagon-like peptide 1 (iGLP-1), ghrelin and hunger and satiety scores. Overall postprandial AUC_glucose was reduced by 12% in PBdiet and by 19% in WBdiet, compared with CBdiet (P<.0001). Compared with PBdiet and CBdiet, WBdiet led to a greater postprandial overall AUC for insulin, C-peptide, iGLP-1 and satiety scores, while postprandial overall AUC for ghrelin and hunger scores were reduced (P<.0001). After 12 weeks, HbA_1C was reduced after WBdiet by 0.89±0.05% (11.5±0.6 mmol/mol), after PBdiet by 0.6±0.04% (7.1±0.31 mmol/mol) and after CBdiet by 0.36±0.04% (2.9±0.31 mmol/mol) (P<.0001). Furthermore, the participants on WBdiet lost 7.6±0.3 kg, PBdiet 6.1±0.3 kg and CBdiet 3.5±0.3 kg (P<.0001). Whey protein-based breakfast is an important adjuvant in the management of Type 2 diabetes.

Effect of two bakery products on short-term food intake and gut-hormones in young adults: a pilot study

The aim of this study is to compare the effect of conventional bread and a whole grain bread on appetite and energy intake, satiety and satiety gut-hormones. A randomized controlled crossover pilot study was carried out in 11 university students (age: 18.7 ± 0.9 years; body mass index: 22.7 ± 2.7 kg/m(2)). Participants consumed two different mid-morning cereal-based snacks, including a conventional or whole grain bread. Two testing days were completed, including satiety questionnaires, blood sampling and consumption of standardized breakfast, mid-morning test-snacks and ad libitum lunch. Several gut-hormones were analysed and satiation was assessed using Visual Analogue Scale scores. The consumption of whole grain bread increased satiety perception, decreased the remained energy intake during the testing day, and decreased the postprandial response of peptide YY, compared with conventional bread (p < 0.005). These data suggest that the consumption of whole grain bread might be a useful strategy to improve satiety.

Effects of Higher Dietary Protein and Fiber Intakes at Breakfast on Postprandial Glucose, Insulin, and 24-h Interstitial Glucose in Overweight Adults

Dietary protein and fiber independently influence insulin-mediated glucose control. However, potential additive effects are not well-known. Men and women (n = 20; age: 26 ± 5 years; body mass index: 26.1 ± 0.2 kg/m²; mean ± standard deviation) consumed normal protein and fiber (NPNF; NP = 12.5 g, NF = 2 g), normal protein and high fiber (NPHF; NP = 12.5 g, HF = 8 g), high protein and normal fiber (HPNF; HP = 25 g, NF = 2 g), or high protein and fiber (HPHF; HP = 25 g, HF = 8 g) breakfast treatments during four 2-week interventions in a randomized crossover fashion. On the last day of each intervention, meal tolerance tests were completed to assess postprandial (every 60 min for 240 min) serum glucose and insulin concentrations. Continuous glucose monitoring was used to measure 24-h interstitial glucose during five days of the second week of each intervention. Repeated-measures ANOVA was applied for data analyses. The HPHF treatment did not affect postprandial glucose and insulin responses or 24-h glucose total area under the curve (AUC). Higher fiber intake reduced 240-min insulin AUC. Doubling the amount of protein from 12.5 g to 25 g/meal and quadrupling fiber from 2 to 8 g/meal at breakfast was not an effective strategy for modulating insulin-mediated glucose responses in these young, overweight adults.

Effect of macronutrients and fiber on postprandial glycemic responses and meal glycemic index and glycemic load value determinations

Background: The potential confounding effect of different amounts and proportions of macronutrients across eating patterns on meal or dietary glycemic index (GI) and glycemic load (GL) value determinations has remained partially unaddressed.Objective: The study aimed to determine the effects of different amounts of macronutrients and fiber on measured meal GI and GL values.Design: Four studies were conducted during which participants [n = 20-22; women: 50%; age: 50-80 y; body mass index (in kg/m²): 25-30)] received food challenges containing different amounts of the variable nutrient in a random order. Added to the standard 50 g available carbohydrate from white bread was 12.5, 25, or 50 g carbohydrate; 12.5, 25, or 50 g protein; and 5.6, 11.1, or 22.2 g fat from rice cereal, tuna, and unsalted butter, respectively, and 4.8 or 9.6 g fiber from oat cereal. Arterialized venous blood was sampled for 2 h, and measured meal GI and GL and insulin index (II) values were calculated by using the incremental area under the curve (AUC_i) method.Results: Adding carbohydrate to the standard white-bread challenge increased glucose AUC_i (P < 0.0001), measured meal GI (P = 0.0066), and mean GL (P < 0.0001). Adding protein (50 g only) decreased glucose AUC_i (P = 0.0026), measured meal GI (P = 0.0139), and meal GL (P = 0.0140). Adding fat or fiber had no significant effect on these variables. Adding carbohydrate (50 g), protein (50 g), and fat (11.1 g) increased the insulin AUC_i or II; fiber had no effect.Conclusions: These data indicate that uncertainty in the determination of meal GI and GL values is introduced when carbohydrate-containing foods are consumed concurrently with protein (equal amount of carbohydrate challenge) but not with carbohydrate-, fat-, or fiber-containing foods. Future studies are needed to evaluate whether this uncertainty also influences the prediction of average dietary GI and GL values for eating patterns. This trial was registered at clinicaltrials.gov as NCT01023646.

Effect on Nitrogen Balance, Thermogenesis, Body Composition, Satiety, and Circulating Branched Chain Amino Acid Levels up to One Year after Surgery: Protocol of a Randomized Controlled Trial on Dietary Protein During Surgical Weight Loss

Background

Bariatric surgery (BS), the most effective treatment for severe obesity, typically results in 40-50 kg weight loss in the year following the surgery. Beyond its action on protein metabolism, dietary protein intake (PI) affects satiety, thermogenesis, energy efficiency, and body composition (BC). However, the required amount of PI after surgical weight loss is not known. The current daily PI recommendation for diet-induced weight loss is 0.8 g/kg ideal body weight (IBW) per day, but whether this amount is sufficient to preserve fat-free mass during active surgical weight loss is unknown.

Objective

To evaluate the effect of a 3-month dietary protein supplementation (PS) on nitrogen balance (NB), BC, energy expenditure, and satiety in women undergoing either gastric bypass or vertical sleeve gastrectomy.

Methods

In this randomized prospective study, participants will be randomized to a high protein supplementation group (1.2 g/kg IBW per day) or standard protein supplementation group (0.8 g/kg IBW per day) based on current guidelines. Outcome measures including NB, BC, circulating branched chain amino acids, and satiety, which will be assessed presurgery, and at 3-months and 12-months postsurgery.

Results

To date, no studies have examined the effect of dietary PS after BS. Current guidelines for PI after surgery are based on weak evidence.

Conclusions

The results of this study will contribute to the development of evidence-based data regarding the safe and optimal dietary PI and supplementation after BS.

Trial Registration

Clinicaltrials.gov NCT02269410; http://clinicaltrials.gov/ct2/show/NCT02269410 (Archived by WebCite at http://www.webcitation.org/6m2f2QLeg).

Raised FGF-21 and Triglycerides Accompany Increased Energy Intake Driven by Protein Leverage in Lean, Healthy Individuals: A Randomised Trial

A dominant appetite for protein drives increased energy intake in humans when the proportion of protein in the diet is reduced down to approximately 10% of total energy. Compensatory feeding for protein is apparent over a 1–2 d period but the mechanisms driving this regulation are not fully understood. Fibroblast growth factor-21 (FGF-21) has been identified as a candidate protein signal as levels increase in the circulation when dietary protein is low. The aim of this randomised controlled trial was to assess whether changes in percent dietary protein over a 4 d ad libitum experimental period in lean, healthy participants influenced energy intake, metabolic health, circulating FGF-21 and appetite regulating hormones including ghrelin, glucagon like peptide-1 and cholecystokinin. Twenty-two lean, healthy participants were fed ad libitum diets containing 10, 15 and 25% protein, over three, 4 d controlled, in-house experimental periods. Reduced dietary protein intake from 25% to 10% over a period of 4 d was associated with 14% increased energy intake (p = 0.02) as previously reported, and a 6-fold increase in fasting circulating plasma FGF-21 levels (p<0.0001), a 1.5-fold increase in serum triglycerides (p<0.0001), and a 0.9-fold decrease in serum total cholesterol (p = 0.02). Serum HDL cholesterol was reduced with a reduction in dietary protein from 15% to 10% (p = 0.01) over 4 d but not from 25% to 10% (p = 0.1) and the change from baseline was not different between diets. Plasma fasting insulin levels following the 4 d study period were significantly lower following the 25% ad libitum study period compared to the 15% protein period (p = 0.014) but not the 10% protein period (p = 0.2). Variability in interstitial glucose during each study period increased with a decrease in dietary protein from 25% to 15% and 10% (p = 0.001 and p = 0.04, respectively). Ghrelin, glucagon-like peptide-1 and cholecystokinin were unchanged. Increases in energy intake, plasma FGF-21 and serum triglycerides were associated with reductions in percent dietary protein from 25% to 10% energy over a 4 d ad libitum in-house feeding period and may be important in regulation of dietary protein intake.

Critical review evaluating the pig as a model for human nutritional physiology

The present review examines the pig as a model for physiological studies in human subjects related to nutrient sensing, appetite regulation, gut barrier function, intestinal microbiota and nutritional neuroscience. The nutrient-sensing mechanisms regarding acids (sour), carbohydrates (sweet), glutamic acid (umami) and fatty acids are conserved between humans and pigs. In contrast, pigs show limited perception of high-intensity sweeteners and NaCl and sense a wider array of amino acids than humans. Differences on bitter taste may reflect the adaptation to ecosystems. In relation to appetite regulation, plasma concentrations of cholecystokinin and glucagon-like peptide-1 are similar in pigs and humans, while peptide YY in pigs is ten to twenty times higher and ghrelin two to five times lower than in humans. Pigs are an excellent model for human studies for vagal nerve function related to the hormonal regulation of food intake. Similarly, the study of gut barrier functions reveals conserved defence mechanisms between the two species particularly in functional permeability. However, human data are scant for some of the defence systems and nutritional programming. The pig model has been valuable for studying the changes in human microbiota following nutritional interventions. In particular, the use of human flora-associated pigs is a useful model for infants, but the long-term stability of the implanted human microbiota in pigs remains to be investigated. The similarity of the pig and human brain anatomy and development is paradigmatic. Brain explorations and therapies described in pig, when compared with available human data, highlight their value in nutritional neuroscience, particularly regarding functional neuroimaging techniques.

The Effects of Increased Protein Intake on Fullness: A Meta-Analysis and Its Limitations

BACKGROUND

Higher protein intake has been implicated in weight management because of its appetitive properties. However, the effects of protein intake on appetitive sensations such as fullness have not been systematically assessed. Meta-analysis is a useful technique to evaluate evidence of an intervention's effect on testable outcomes, but it also has important limitations.

OBJECTIVE

The primary aim of this study was to synthesize the available evidence on the effect of protein intake on fullness using a quantitative meta-analysis and a secondary directional analysis using the vote-counting procedure. A tertiary aim was to address limitations of meta-analyses as they pertain to findings from this meta-analysis.

DESIGN

We searched multiple databases for interventional studies that evaluated the effect of increased protein intake on fullness ratings. Inclusion criteria for both analyses were as follows: healthy human participants, preload studies that utilized intact dietary protein, delivery of protein load orally, and studies reporting fullness as an outcome. For the meta-analysis, an additional criterion was that the studies also needed to report 2- to 4-hour area under the curve value for fullness.

RESULTS

Five studies met all criteria for the meta-analysis. Twenty-eight studies met all criteria for the directional analysis. The meta-analysis indicated higher protein preloads have a greater effect on fullness than lower protein preloads (overall effect estimate: 2,435.74 mm.240 min, (95% CI 1,375.18 to 3,496.31 mm.240 min; P<0.0001). The directional analysis also revealed a positive effect on fullness with higher protein preloads (P<0.01). Many related scientifically rigorous studies were excluded from the analysis because analytical criteria required a narrowly focused research question.

CONCLUSIONS

The present analyses show that higher protein preloads increase fullness ratings more than lower protein preloads under tightly defined conditions. Extrapolation of findings to common conditions outside the specified criteria of this analysis must be made cautiously, as must speculation about the influence of fullness sensations on ingestive behavior, body weight, and various health outcomes.

In vitro bioactive properties of intact and enzymatically hydrolysed whey protein: targeting the enteroinsular axis

Enzymatically hydrolysed milk proteins have a variety of biofunctional effects some of which may be beneficial in the management of type 2 diabetes mellitus. The purpose of this study was to evaluate the effect of commercially available intact and hydrolysed whey protein ingredients (DH 32, DH 45) on markers of the enteroinsular axis (glucagon like peptide-1 secretion, dipeptidyl peptidase IV inhibition, insulin secretion and antioxidant activity) before and after simulated gastrointestinal digestion (SGID). A whey protein hydrolysate, DH32, significantly enhanced (P < 0.05) insulin secretion from BRIN BD11 β-cells compared to the positive control (16.7 mM glucose and 10 mM Ala). The whey protein hydrolysates inhibited dipeptidyl peptidase IV activity, yielding half maximal inhibitory concentration values (IC50) of 1.5 ± 0.1 and 1.1 ± 0.1 mg mL(-1) for the DH 32 and DH 45, samples respectively, and were significantly more potent than the intact whey (P < 0.05). Enzymatic hydrolysis of whey protein significantly enhanced (P < 0.05) its antioxidant activity compared to intact whey, as measured by the oxygen radical absorbance capacity assay (ORAC). This antioxidant activity was maintained (DH 32, P > 0.05) or enhanced (DH 45, P < 0.05) following SGID. Intact whey stimulated GLP-1 secretion from enteroendocrine cells compared to vehicle control (P < 0.05). This data confirm that whey proteins and peptides can act through multiple targets within the enteroinsular axis and as such may have glucoregulatory potential.

Acute load-dependent effects of oral whey protein on gastric emptying, gut hormone release, glycemia, appetite, and energy intake in healthy men

BACKGROUND

In healthy individuals, intraduodenal whey protein load-dependently modulates gastrointestinal motor and hormonal functions and suppresses energy intake. The effect of oral whey, particularly the impact of load, has not been evaluated.

OBJECTIVE

The purpose of this study was to quantify gastric emptying of 30 and 70 g of oral whey protein loads and their relation to gastrointestinal hormone, glycemic, and appetitive responses.

DESIGN

On 3 separate occasions in a randomized, double-blind order, 18 lean men [mean ± SEM age: 24.8 ± 1.4 y; body mass index (in kg/m(2)): 21.6 ± 0.5] received iso-osmolar, equally palatable drinks (∼450 mL) containing 30 g pure whey protein isolate (L), 70 g pure whey protein isolate (H), or saline (control). Gastric emptying (with the use of 3-dimensional ultrasound), plasma cholecystokinin, glucagon-like peptide 1, glucose-dependent insulinotropic peptide, insulin, glucagon, total amino acids, and blood glucose were measured for 180 min after consumption of the drinks, and energy intake at a buffet-style lunch was quantified.

RESULTS

Gastric emptying of the L and H drinks was comparable when expressed in kilocalories per minute (L: 2.6 ± 0.2 kcal/min; H: 2.9 ± 0.3 kcal/min) and related between individuals (r = 0.54, P < 0.01). Gastrointestinal hormone, insulin, and glucagon responses to the L and H drinks were comparable until ∼45-60 min after ingestion, after which time the responses became more differentiated. Blood glucose was modestly reduced after the H drink between t = 45 and 150 min when compared with the L drink (all P < 0.05). Energy intake was suppressed by both L and H drinks compared with control (P < 0.05) (control: 1174 ± 91 kcal; L: 1027 ± 81 kcal; and H: 997 ± 71 kcal).

CONCLUSION

These findings indicate that, in healthy lean men, the rate of gastric emptying of whey protein is independent of load and determines the initial gastrointestinal hormone response. This study was registered at www.anzctr.org.au as 12611000706976.