Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum

Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome

PURPOSE OF REVIEW

The goal of this paper is to review current literature on nutritional ketosis within the context of weight management and metabolic syndrome, namely, insulin resistance, lipid profile, cardiovascular disease risk, and development of non-alcoholic fatty liver disease. We provide background on the mechanism of ketogenesis and describe nutritional ketosis.

RECENT FINDINGS

Nutritional ketosis has been found to improve metabolic and inflammatory markers, including lipids, HbA1c, high-sensitivity CRP, fasting insulin and glucose levels, and aid in weight management. We discuss these findings and elaborate on potential mechanisms of ketones for promoting weight loss, decreasing hunger, and increasing satiety. Humans have evolved with the capacity for metabolic flexibility and the ability to use ketones for fuel. During states of low dietary carbohydrate intake, insulin levels remain low and ketogenesis takes place. These conditions promote breakdown of excess fat stores, sparing of lean muscle, and improvement in insulin sensitivity.

Effects of Weight-Loss Interventions on Short-Chain Fatty Acid Concentrations in Blood and Feces of Adults: A Systematic Review

Short-chain fatty acids (SCFAs, mainly acetate, propionate, and butyrate), which are primarily derived from the gut microbiome, may exert anti-inflammatory and immunomodulatory effects, and regulate energy homeostasis. It has been suggested that weight loss may affect SCFA metabolism, but a systematic review of intervention studies is lacking. We aimed to systematically assess the effects of dietary, physical activity-based, and surgical weight-loss interventions among overweight [body mass index (BMI) 25-29.9 kg/m2)] or obese (BMI ≥30 kg/m2) adults (≥18 y) on concentrations of acetate, propionate, butyrate, and total SCFAs in blood, urine, or feces. We conducted a systematic literature search in PubMed, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) up to April 30, 2018 for randomized and nonrandomized weight-loss trials among overweight or obese adults, in which the concentrations of individual and total SCFAs were assessed. A total of 9 studies consisting of 2 randomized parallel-arm trials, 4 crossover trials, and 3 nonrandomized clinical or surgical trials were included. In the majority of studies, changes in fecal SCFA concentrations were assessed, whereas changes in serum SCFAs were reported from 1 trial. Individual and total SCFA concentrations either remained unchanged or decreased significantly following weight loss. Three of the dietary interventions that resulted in decreased SCFA concentrations were low (≤5% of energy) in total carbohydrates. Most of the studies had a high risk of bias. Decreases in SCFA concentrations may accompany weight loss induced by bariatric surgery or dietary restriction among overweight or obese adults, particularly when carbohydrate intake is reduced. However, findings were inconsistent and based on studies with high to unclear risk of bias, and small sample sizes. Because measurements of fecal SCFAs may not be ideal due to limited sample standardization, well-powered trials with repeated blood measurements of SCFAs are required. This review was registered at PROSPERO as CRD42018088716.

[Ketogenic Diet and its Evidence-Based Therapeutic Implementation in Endocrine Diseases]

Ketogenic Diet and its Evidence-Based Therapeutic Implementation in Endocrine Diseases Abstract. Abstract: The ketogenic diet (KD) is a high-fat and very low-carb diet, which has been used primarily for treatment of therapy-resistant epilepsy in children. Implementation of the KD in other target populations is increasingly being discussed. This literature review provides first indications for a clinical benefit of the KD in diabetes mellitus type 2 (T2DM) and polycystic ovarian syndrome (PCOS). In many analysed studies, KD led to significant weight loss and had beneficial effects on lipoprotein profile and insulin resistance. In half of the comparative studies with T2DM, the KD lead to signifiantly greater reductions in HbA1c-levels (HbA1c difference: -0.5 to -1.5 %) compared to reference diets (HbA1c difference: +0.2 to -0.5 %). Nevertheless, study results are too heterogenic for a general recommendation of the KD in this patient population.

Investigating the effect of sex and ketosis on weight-loss-induced changes in appetite

BACKGROUND

Diet-induced weight loss (WL) is usually accompanied by increased appetite, a response that seems to be absent when ketogenic diets are used. It remains unknown if sex modulates the appetite suppressant effect of ketosis.

OBJECTIVE

The aim of this study was to examine if sex modulates the impact of WL-induced changes in appetite and if ketosis alters these responses.

METHODS

Ninety-five individuals (55 females) with obesity (BMI [kg/m 2]: 37  ± 4) underwent 8 wk of a very-low-energy diet, followed by 4 wk of refeeding and weight stabilization. Body composition, plasma concentration of β-hydroxybutyrate (β-HB) and appetite-related hormones (active ghrelin, active glucagon-like peptide 1 [GLP-1], total peptide YY [PYY], cholecystokinin and insulin), and subjective feelings of appetite were measured at baseline, week 9 in ketosis, and week 13 out of ketosis.

RESULTS

The mean WL at week 9 was 17% for males and 15% for females, which was maintained at week 13. Weight, fat, and fat-free mass loss were greater in males (P < 0.001 for all) and the increase in β-HB at week 9 higher in females (1.174 ± 0.096 compared with 0.783 ± 0.112 mmol/L, P = 0.029). Basal and postprandial GLP-1 and postprandial PYY (all P < 0.05) were significantly different for males and females. There were no significant sex × time interactions for any other appetite-related hormones or subjective feelings of appetite. At week 9, basal GLP-1 was decreased only in males (P < 0.001), whereas postprandial GLP-1 was increased only in females (P < 0.001). No significant changes in postprandial PYY were observed over time for either sex.

CONCLUSIONS

Ketosis appears to have a greater beneficial impact on GLP-1 in females. However, sex does not seem to modulate the changes in the secretion of other appetite-related hormones, or subjective feelings of appetite, seen with WL, regardless of the ketotic state. This trial was registered at clinicaltrials.gov as NCT01834859.

Concentration-Dependent Effects of a Dietary Ketone Ester on Components of Energy Balance in Mice

Objectives: Exogenous ketones may provide therapeutic benefit in treatment of obesity. Administration of the ketone ester (KE) R,S-1,3-butanediol acetoacetate diester (BD-AcAc2) decreases body weight in mice, but effects on energy balance have not been extensively characterized. The purpose of this investigation was to explore concentration-dependent effects of BD-AcAc2 on energy intake and expenditure in mice. Methods: Forty-two male C57BL/6J mice were randomly assigned to one of seven isocaloric diets (n = 6 per group): (1) Control (CON, 0% KE by kcals); (2) KE5 (5% KE); (3) KE10 (10% KE); (4) KE15 (15% KE); (5) KE20 (20% KE); (6) KE25 (25% KE); and (7) KE30 (30% KE) for 3 weeks. Energy intake and body weight were measured daily. Fat mass (FM), lean body mass (LBM), and energy expenditure (EE) were measured at completion of the study. Differences among groups were compared to CON using ANOVA and ANCOVA. Results: Mean energy intake was similar between CON and each concentration of KE, except KE30 which was 12% lower than CON (P < 0.01). KE25 and KE30 had lower body weight and FM compared to CON, while only KE30 had lower LBM (P < 0.03). Adjusted resting and total EE were lower in KE30 compared to CON (P < 0.03), but similar for all other groups. Conclusions: A diet comprised of 30% energy from BD-AcAc2 results in lower energy intake, coincident with lower body weight and whole animal adiposity; while KE20 and KE25 have significantly lower body weight and adiposity effects independent of changes in energy intake or expenditure.

Bone microstructure and metabolism changes under the combined intervention of ketogenic diet with intermittent fasting: an in vivo study of rats

Ketogenic diet (KD) has been used in epilepsy for decades, but previous studies found it may cause severe bone loss. Every-other-day ketogenic diet (EODKD), the combination of KD with intermittent fasting, showed better potential for seizure control recently, while its effects on bone remain unknown. This study aims to establish different ketogenic rat models and compare the influence of EODKD with KD on bone microstructure and metabolism. Thirty male Sprague-Dawley rats were divided into Control, KD and EODKD groups, fed with standard diet, continuous and intermittent ketogenic diet respectively. After 12 weeks, bone mineral density (BMD) and body fat percentage were obtained by dual energy X-ray absorptiometry. Micro-CT and three-point bending test were used to evaluate the bone microstructure and mechanical properties. Activities of serum alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) were measured, together with the osteogenic capabilities of bone marrow stromal cells (BMSCs) tested by ALP activities and alizarin red stain in different osteogenic stage. Both EODKD and KD induced higher ketone and more fat percentage, but led to lower body weight compared with Control group. They both compromised bone mass and mechanical properties. Compared with KD, EODKD demonstrated higher ketone levels, but it also inhibited osteoclastic process as well as early osteogenic differentiation. In general, EODKD accelerated ketosis, but may not deteriorate bone microstructure and strength than KD.

Post hoc analyses of surrogate markers of non-alcoholic fatty liver disease (NAFLD) and liver fibrosis in patients with type 2 diabetes in a digitally supported continuous care intervention: an open-label, non-randomised controlled study

OBJECTIVE

One year of comprehensive continuous care intervention (CCI) through nutritional ketosis improves glycosylated haemoglobin(HbA1c), body weight and liver enzymes among patients with type 2 diabetes (T2D). Here, we report the effect of the CCI on surrogate scores of non-alcoholic fatty liver disease (NAFLD) and liver fibrosis.

METHODS

This was a non-randomised longitudinal study, including adults with T2D who were self-enrolled to the CCI (n=262) or to receive usual care (UC, n=87) during 1 year. An NAFLD liver fat score (N-LFS) >-0.640 defined the presence of fatty liver. An NAFLD fibrosis score (NFS) of >0.675 identified subjects with advanced fibrosis. Changes in N-LFS and NFS at 1 year were the main endpoints.

RESULTS

At baseline, NAFLD was present in 95% of patients in the CCI and 90% of patients in the UC. At 1 year, weight loss of ≥5% was achieved in 79% of patients in the CCI versus 19% of patients in UC (p<0.001). N-LFS mean score was reduced in the CCI group (-1.95±0.22, p<0.001), whereas it was not changed in the UC (0.47±0.41, p=0.26) (CCI vs UC, p<0.001). NFS was reduced in the CCI group (-0.65±0.06, p<0.001) compared with UC (0.26±0.11, p=0.02) (p<0.001 between two groups). In the CCI group, the percentage of individuals with a low probability of advanced fibrosis increased from 18% at baseline to 33% at 1 year (p<0.001).

CONCLUSIONS

One year of a digitally supported CCI significantly improved surrogates of NAFLD and advanced fibrosis in patients with T2D.

TRIAL REGISTRATION NUMBER

NCT02519309; Results.

Low-carbohydrate diets differing in carbohydrate restriction improve cardiometabolic and anthropometric markers in healthy adults: A randomised clinical trial

BACKGROUND

Low-carbohydrate, high-fat (LCHF) diets are useful for treating a range of health conditions, but there is little research evaluating the degree of carbohydrate restriction on outcome measures. This study compares anthropometric and cardiometabolic outcomes between differing carbohydrate-restricted diets.

OBJECTIVE

Our hypothesis was that moderate carbohydrate restriction is easier to maintain and more effective for improving cardiometabolic health markers than greater restriction.

DESIGN

A total of 77 healthy participants were randomised to a very low-carbohydrate ketogenic diet (VLCKD), low-carbohydrate diet (LCD), or moderate-low carbohydrate diet (MCD), containing 5%, 15% and 25% total energy from carbohydrate, respectively, for 12-weeks. Anthropometric and metabolic health measures were taken at baseline and at 12 weeks. Using ANOVA, both within and between-group outcomes were analysed.

RESULTS

Of 77 participants, 39 (51%) completed the study. In these completers overall, significant reductions in weight and body mass index occurred ((mean change) 3.7 kg/m2; 95% confidence limits (CL): 3.8, 1.8), along with increases in high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, (0.49 mmol/L; 95% CL; 0.06, 0.92; p = 0.03), and total cholesterol concentrations (0.11 mmol/L; 95% CL; 0.00, 0.23; p = 0.05). Triglyceride (TG) levels were reduced by 0.12 mmol/L (95% CL; -0.20, 0.02; p = 0.02). No significant changes occurred between groups. The largest improvements in high density lipoprotein cholesterol (HDL-c) and TG and anthropometric changes occurred for the VLCKD group.

CONCLUSIONS

Low-carbohydrate, high-fat diets have a positive effect on markers of health. Adherence to the allocation of carbohydrate was more easily achieved in MCD, and LCD groups compared to VLCKD and there were comparable improvements in weight loss and waist circumference and greater improvements in HDL-c and TG with greater carbohydrate restriction.

Bone loss and biomechanical reduction of appendicular and axial bones under ketogenic diet in rats

A ketogenic diet (KD) is composed of low-carbohydrate, high-fat and adequate levels of protein. It has been used for decades as a method to treat pediatric refractory epilepsy. However, recently, its side effects on the bones have received increasing attention. In order to comprehensively evaluate the effect of KD on the microstructures and mechanical properties of the skeleton, 14 male Sprague-Dawley rats were equally divided into two groups and fed with a KD (ratio of fat to carbohydrate and protein, 3:1) or a standard diet for 12 weeks. Body weight, as well as blood ketone and glucose levels, were monitored during the experiment. Bone morphometric analyses via micro-computerized tomography were performed on cortical and trabecular bone at the middle L4 vertebral body, the proximal humerus and tibia. The compressive stiffness and strength of scanned skeletal areas were calculated using micro-finite element analysis. The KD led to higher ketone levels and lower glucose levels, with reduced body weight and total bone mineral density (TBMD). After 12 weeks, the diet reduced the bone volume fraction, the trabecular number of cancellous bone, cortical thickness, total cross-sectional area inside the periosteal envelope and the bone area of cortical bone in the tibia and humerus, while increasing trabecular separation. However, KD may not affect the L4 vertebral body. The serum calcium or phosphate concentrations in the blood remained unchanged. In addition, bone stiffness and strength were clearly decreased by the KD, and significantly correlated with the BMD and bone area at all scanned sites. In conclusion, KD led to significant bone loss and reduced biomechanical function in appendicular bones, with a lesser impact on axial bones.

Associations of specific dietary protein with longitudinal insulin resistance, prediabetes and type 2 diabetes: The Rotterdam Study

BACKGROUND & AIMS

High protein intake has been linked to increased type 2 diabetes (T2D) risk. However, if this association differs by protein from specific food sources, and if a habitual high protein intake affects insulin resistance and prediabetes risk are largely unknown. We aimed to investigate associations between protein intake from different food sources with longitudinal insulin resistance, and risk of prediabetes and T2D.

METHODS

Our analyses included 6822 participants aged ≥45 years without diabetes at baseline in three sub-cohorts of the prospective population-based Rotterdam Study. We measured protein intake at baseline using food-frequency questionnaires. Data on longitudinal homeostatic model assessment of insulin resistance (HOMA-IR), and incidence of prediabetes and T2D were available from 1993 to 2014.

RESULTS

During follow-up, we documented 931 prediabetes cases and 643 T2D cases. After adjusting for sociodemographic, lifestyle, and dietary factors, higher total protein intake was associated with higher longitudinal HOMA-IR and with higher risk of prediabetes and T2D (per 5% increment in energy from protein at the expense of carbohydrate, for HOMA-IR: β = 0.10, (95%CI 0.07, 0.12); for prediabetes: HR = 1.34 (1.24 1.44); for T2D: HR = 1.37 (1.26, 1.49)). These associations were mainly driven by total animal protein (for HOMA-IR: 0.10 (0.07, 0.12); for prediabetes: 1.35 (1.24, 1.45); for T2D: 1.37 (1.26; 1.49)). The harmful associations of total animal protein were contributed to by protein from meat, fish, and dairy (e.g. for HOMA-IR: protein from meat, 0.13 (0.10, 0.17); from fish, 0.08 (0.03, 0.13); from dairy, 0.04 (0.0003, 0.08)). After additional adjustment for longitudinal waist circumference, associations of total protein and total animal protein with longitudinal HOMA-IR and prediabetes risk were attenuated, but remained statistically significant. Total plant protein, as well as protein from legumes and nuts, from grains, from potatoes, or from fruits and vegetables, was not associated with any of the outcomes.

CONCLUSIONS

Higher intake of animal protein, from meat, dairy and fish food sources, is associated with higher longitudinal insulin resistance and risk of prediabetes and T2D, which may be partly mediated by obesity over time. Furthermore, plant protein from different sources is not related to insulin resistance, and risk of prediabetes and T2D. Our findings highlight the importance of specific protein food sources and that habitual high animal protein intake may already in early stages be harmful in the development of T2D.

Effects of differing levels of carbohydrate restriction on mood achievement of nutritional ketosis, and symptoms of carbohydrate withdrawal in healthy adults: A randomized clinical trial

OBJECTIVES

To our knowledge, minimal research exists on the effects of diets differing in carbohydrate restriction on symptoms of carbohydrate withdrawal and mood, and the achievement of nutritional ketosis (NK). The aim of this study was to compare ketonaemia, symptoms of carbohydrate withdrawal, and mood. We hypothesized that a moderate carbohydrate restriction would result in fewer symptoms and a reduced effect on mood.

METHODS

Seventy-seven healthy participants (25 men and 52 women; mean age: 39 y, range: 25-49; mean body mass index 27 kg/m², range: 20-39) were randomized to receive either a very-low-carbohydrate ketogenic diet (VLCKD), low-carbohydrate diet (LCD), or moderately low-carbohydrate diet (MCD), containing 5%, 15%, and 25% total energy (TE) from carbohydrate, respectively, for 3 wk. Fasting blood ketone measures were recorded daily upon waking along with a data from symptom questionnaire and a 5-point mood-state scale. Using analysis of variance and a 5% two-sided α level to determine statistical significance, between-group outcomes were analyzed. Additional association and analyses were conducted by multiple linear regression.

RESULTS

In 75 of 77 initial participants included for analysis, mean serum levels of β-hydroxybutyrate (βOHB) were increased by 0.27 ± 0.32, 0.41 ± 0.38, and 0.62 ± 0.49 mmol/L for MCD, LCD, and VLCKD, respectively (P = 0.013). The achievement of NK was consistent for both VLCKD and LCD groups and sporadic for the MCD group. Only the VLCKD group exhibited 95% confidence interval levels that were consistently ≥0.5 mmol/L. The overall mean change in sum of symptoms scores (SOSS) from baseline was 0.81 ± 2.84 (P < 0.001). Changes in SOSS were highest in the VLCKD group (1.49 ± 2.47), followed by LCD (0.65 ± 2.70) and MCD (0.18 ± 3.3; P = 0.264). Small, statistically significant increases were seen for headache severity, constipation, diarrhea, halitosis, muscle cramps and muscle weakness, and light-headedness, whereas intestinal bloating and craving for sugar and starch improved from baseline. Only halitosis (P = 0.039) and muscle weakness (P = 0.005) differed significantly between the groups. Mood improved significantly from baseline overall, but there was no significant difference between groups (P = 0.181) CONCLUSIONS: Diets containing 5% TE from carbohydrates are ketogenic, but diets containing between 15% and 25% TE from carbohydrates can also result in mean βOHB ≥0.5 mmol/L. There was no meaningful difference in symptoms of carbohydrate withdrawal between diets that contain 5% to 25% TE from carbohydrate, and mood was improved overall, with no significant difference between interventions. Our conclusion, therefore, is that reduced carbohydrate diets should be prescribed by need rather than the desire to mitigate symptoms of carbohydrate withdrawal.

Effects of Ad libitum Low-Carbohydrate High-Fat Dieting in Middle-Age Male Runners

PURPOSE

This study examined the effects of a 3-wk ad libitum, low-carbohydrate (<50 g·d) high-fat (~70% of calories) (LCHF) diet on markers of endurance performance in middle-age, recreationally competitive male runners.

METHODS

All subjects (n = 8) after their normal high-carbohydrate (HC) diet had anthropometric measures assessed and completed five 10-min running bouts at multiple individual race paces in the heat while physiological variables, metabolic variables, and perceptual responses were recorded. After 20 min of rest, participants completed a 5-km time trial on a road course. Subjects then consumed an LCHF diet for 3 wk and returned for repeat testing.

RESULTS

Body mass and seven-site skinfold thickness sum decreased by approximately 2.5 kg (P < 0.01) and 13 mm (P < 0.05) after LCHF diet. Rectal temperature was higher after the first 10 min of exercise (37.7°C ± 0.3°C vs 37.3°C ± 0.2°C) in the HC diet but did not differ at any other time with LCHF diet. Heart rate and perceptual measures did not display any consistent differences between treatments excluding thirst sensation for LCHF diet. RER and carbohydrate oxidation declined significantly, whereas fat oxidation increased after LCHF diet for every pace (P < 0.01). There was no significant difference (P = 0.25) in a 5-km time trial performance, but LCHF diet (23.45 ± 2.25 min) displayed a trend of improved performance versus HC (23.92 ± 2.57 min).

CONCLUSION

Improved body composition and fat oxidation from LCHF diet potentially negate expected performance decrement from reduced carbohydrate use late in exercise for nonelite runners. An acute decrease in training capacity is expected; however, if performance improvement is not exhibited after 3 wk, diet cessation is suggested for negative responders.

Three-Year Chronic Consumption of Low-Carbohydrate Diet Impairs Exercise Performance and Has a Small Unfavorable Effect on Lipid Profile in Middle-Aged Men

The objective of this research was to determine whether chronic (average 3.58 ± 1.56 years) deliberate adherence to low carbohydrate diets (LCDs) is associated with selected markers of metabolism, risk factors of cardiovascular disease (CVD), body mass and physical performance in apparently healthy middle-aged men (n = 12). The control group comprised age, body mass and height matched men using mixed diets (MDs). The diets used were registered for 7 days and analyzed in terms of the energy, carbohydrate, fat and protein contents. It was found that the diets used were isoenergetic, yet varied considerably in carbohydrate and fat content. The LCDs significantly intensified the ketogenesis process, increased resting blood total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and heart rate, (HR) and decreased respiratory exchange ratio (RER) in relation to MD subjects. An exercise trial revealed significant impairment of exercise in subjects following the LCDs. The results showed that in the case where the subjects of two investigated groups did not differ in their somatic variables, long-term adherence to the LCDs was associated with substantially reduced exercise performance in apparently healthy subjects, along with an association with a small unfavorable effect on their lipid profile.

Two-Week Exclusive Supplementation of Modified Ketogenic Nutrition Drink Reserves Lean Body Mass and Improves Blood Lipid Profile in Obese Adults: A Randomized Clinical Trial

The ketogenic diet has long been recommended in patients with neurological disorders, and its protective effects on the cardiovascular system are of growing research interest. This study aimed to investigate the effects of two-week of low-calorie ketogenic nutrition drinks in obese adults. Subjects were randomized to consume drinks either a ketone-to-non-ketone ratio of 4:1 (KD 4:1), a drink partially complemented with protein at 1.7:1 (KD 1.7:1), or a balanced nutrition drink (BD). Changes in body weight, body composition, blood lipid profile, and blood ketone bodies were investigated. Blood ketone bodies were induced and maintained in the group that consumed both 4:1 and 1.7:1 ketogenic drinks (p < 0.001). Body weight and body fat mass significantly declined in all groups between 0 and 1 week and between 1 and 2 weeks (p < 0.05), while skeletal muscle mass remained unchanged only in the KD 1.7:1 group (p > 0.05). The blood lipid profile improved, appetite was reduced, and fullness was maintained in the two ketogenic drink groups. This study indicates the possibility for the development of obesity treatments based on ketogenic nutrition drinks even with a moderate ketogenic ratio of 1.7:1, as well as adjuvant therapies based on ketosis induction and maintenance for the treatment of other diseases and health conditions.

Changes in food reward during weight management interventions - a systematic review

BACKGROUND

Does food reward increase or decrease during weight management attempts? Excessive food intake is the main behavioural determinant of obesity; therefore, a better understanding of food reward and its relationship with food intake and weight outcomes could contribute to more effective weight management solutions.

METHODS

This systematic review assessed the role of changes in food reward (directly or indirectly measured) during weight management interventions. Four databases were searched for articles published until April 2018 involving weight management interventions (all types and designs) in healthy adults with overweight or obesity.

RESULTS

Of 239 full-text articles assessed, 17 longitudinal studies were included. Twelve studies reported a significant change in food reward over time. When compared with control interventions, dietary, pharmacological, behavioural and cognitive interventions were effective in decreasing liking and/or wanting for high-energy food using a range of methodologies to assess food reward. Three studies reported that decreased food reward was associated with improved weight management outcomes.

CONCLUSION

Food reward appears to decrease rather than increase during weight management interventions. Future studies specifically targeting the hedonic aspects of food intake (liking/wanting) are needed to gain a better understanding of how to uncouple the obesogenic relationship between food reward and overeating.

Weight loss, improved physical performance, cognitive function, eating behavior, and metabolic profile in a 12-week ketogenic diet in obese adults

The ketogenic diet (KD) is being increasingly promoted as a strategy to fight obesity. Although the KD is effective for weight loss and weight control, comprehensive determination of its relationship with biochemical, physiological and psychological changes is still largely unexplored. We hypothesized that a 12-week KD (12KD) would significantly affect body weight, physical performance, cognitive function, eating behaviors, the metabolic and hormonal profile in obese adults, although differently in men and women. In an uncontrolled intervention, 35 sedentary obese adults (13 men, 25 women), aged 37 ± 7 years with a BMI 36.1 ± 5.6 kg/m² underwent a 12KD between March 2017 and June 2017 at the University of Primorska. The 12KD resulted in decreased appetite, significant weight loss of participants (-18 ± 9 kg men vs. -11 ± 3 kg women; P < .001), decreased emotional and external eating (P < .001 for both), increased body image satisfaction (P < .001) and improved physical performance (P < .001). Biochemically, a significant drop in glucose (P = .026), and a significant increase in LDL-cholesterol (P = .031), CRP (P = .007), and BDNF (P = .035) were observed in the first 2 weeks; then, all listed parameters returned to baseline. On the other hand, a significant reduction in insulin (P < .001) and leptin levels (P < .001), and a significant increase in adiponectin (P = .008) and NPY (P = .009) were detected throughout the duration of the 12KD. Our results show the efficacy of the 12KD on weight loss, physical performance, cognitive function, eating behaviors and metabolic profile. However, the long-term effects of a KD on these outcomes needs to be further studied before general recommendations can be made.

Effect of A Very Low-Calorie Ketogenic Diet on Food and Alcohol Cravings, Physical and Sexual Activity, Sleep Disturbances, and Quality of Life in Obese Patients

Psychological well-being and hunger and food control are two relevant factors involved in the success of weight-loss therapy in treating obesity. Thus, this study aims to evaluate food and alcohol cravings, physical and sexual activity, sleep, and life quality (QoL) in obese patients following a very low-calorie ketogenic (VLCK) diet, as well as the role of weight lost and ketosis on these parameters. A battery of psychological test was performed in twenty obese patients (12 females, 47.2 ± 10.2 year and BMI of 35.5 ± 4.4) through the course of a 4-month VLCK diet on four subsequent visits: baseline, maximum ketosis, reduced ketosis, and endpoint. Each subject acted as their own control. Relevantly, the dietary-induced changes in body composition (7.7 units of BMI lost, 18 kg of fat mass (1.2 kg of visceral fat mass)) were associated with a statistically significant improvement in food craving scores, physical activity, sleepiness, and female sexual function. Overall, these results also translated in a notable enhancement in QoL of the treated obese patients. Therefore, the rapid and sustained weight and fat mass (FM) loss induced by the VLCK diet is associated with good food control and improvements in the psychological well-being parameters in obese subjects, which could contribute to the long-term success of this therapy.

Implementing a low-carbohydrate, ketogenic diet to manage type 2 diabetes mellitus

INTRODUCTION

Type 2 diabetes mellitus (T2DM) has reached epidemic proportions in the modern world. For individuals affected by obesity-related T2DM, clinical studies have shown that carbohydrate restriction and weight loss can improve hyperglycemia, obesity, and T2DM.

AREAS COVERED

Reducing carbohydrate intake to a certain level, typically below 50 g per day, leads to increased ketogenesis in order to provide fuel for the body. Such low-carbohydrate, ketogenic diets were employed to treat obesity and diabetes in the 19^th and early 20^th centuries. Recent clinical research has reinvigorated the use of the ketogenic diet for individuals with obesity and diabetes. Although characterized by chronic hyperglycemia, the underlying cause of T2DM is hyperinsulinemia and insulin resistance, typically as a result of increased energy intake leading to obesity. The ketogenic diet substantially reduces the glycemic response that results from dietary carbohydrate as well as improves the underlying insulin resistance. This review combines a literature search of the published science and practical guidance based on clinical experience.

EXPERT COMMENTARY

While the current treatment of T2DM emphasizes drug treatment and a higher carbohydrate diet, the ketogenic diet is an effective alternative that relies less on medication, and may even be a preferable option when medications are not available.

High protein diets do not affect anthropometric indexes and cardiometabolic risk factors among children with excess weight: A randomized controlled trial

Introduction: Limited information exists regarding the effects of high protein (HP) diets on cardiovascular disease (CVD) risk factors among overweight and obese children. Our aim was to determine the effects of an HP diet on anthropometric indexes and CVD risk factors among overweight and obese children. Methods: In a parallel randomized controlled trial, we recruited 50 overweight and obese children, aged 6-11 years, for a 10 week HP or control diet (protein, carbohydrate, fat: 25%, 45%, 30% in the HP diet vs. 15%, 55%, 30% in the control diet, respectively). Fasting blood glucose (FBG) serum insulin levels, lipid profiles, systolic and diastolic blood pressure (SBP and DBP), and anthropometric measurements were assessed using standard guidelines. Results: 86% of children completed the trial. Percent changes (PC) for anthropometric and biochemical variables were not significantly different between the two groups. The PC of serum triglyceride (TG) level was significantly decreased in the HP group compared to in the control group (PC: -10.16±4.30% vs.12.11±7.80%; P = 0.01) in the crude model, but not in the adjusted model. For other variables, we did not find any significant differences between the HP group and the controls. Conclusion: In the present study, we did not find any significant effect of adherence to an HP diet in improving anthropometric measurements or other CVD risk factors among obese and overweight children.

Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial

BACKGROUND

Ketogenic diets (KD) have become a popular method of promoting weight loss. More recently, some have recommended that athletes adhere to ketogenic diets in order to optimize changes in body composition during training. This study evaluated the efficacy of an 8-week ketogenic diet (KD) during energy surplus and resistance training (RT) protocol on body composition in trained men.

METHODS

Twenty-four healthy men (age 30 ± 4.7 years; weight 76.7 ± 8.2 kg; height 174.3 ± 19.7 cm) performed an 8-week RT program. Participants were randomly assigned to a KD group (n = 9), non-KD group (n = 10, NKD), and control group (n = 5, CG) in hyperenergetic condition. Body composition changes were measured by dual energy X-ray absorptiometry (DXA). Compliance with the ketosis state was monitored by measuring urinary ketones weekly. Data were analyzed using a univariate, multivariate and repeated measures general linear model (GLM) statistics.

RESULTS

There was a significant reduction in fat mass (mean change, 95% CI; p-value; Cohen's d effect size [ES]; - 0.8 [- 1.6, - 0.1] kg; p < 0.05; ES = - 0.46) and visceral adipose tissue (- 96.5 [- 159.0, - 34.0] g; p < 0.05; ES = - 0.84), while no significant changes were observed in the NKD and CG in fat mass (- 0,5 [- 1.2, 0.3] kg; p > 0.05; ES = - 0.17 and - 0,5 [- 2.4, 1.3] kg; p > 0.05; ES = - 0.12, respectively) or visceral adipose tissue (- 33.8 [- 90.4, 22.8]; p > 0.5; ES = - 0.17 and 1.7 [- 133.3, 136.7]; p > 0.05; ES = 0.01, respectively). No significant increases were observed in total body weight (- 0.9 [- 2.3, 0.6]; p > 0.05; ES = [- 0.18]) and muscle mass (- 0.1 [- 1.1,1.0]; p > 0,05; ES = - 0.04) in the KD group, but the NKD group showed increases in these parameters (0.9 [0.3, 1.5] kg; p < 0.05; ES = 0.18 and (1.3[0.5, 2.2] kg; p < 0,05; ES = 0.31, respectively). There were no changes neither in total body weight nor lean body mass (0.3 [- 1.2, 1.9]; p > 0.05; ES = 0.05 and 0.8 [- 0.4, 2.1]; p > 0.05; ES = 0.26, respectively) in the CG.

CONCLUSION

Our results suggest that a KD might be an alternative dietary approach to decrease fat mass and visceral adipose tissue without decreasing lean body mass; however, it might not be useful to increase muscle mass during positive energy balance in men undergoing RT for 8 weeks.

The use of nutritional supplements to induce ketosis and reduce symptoms associated with keto-induction: a narrative review

Background

Adaptation to a ketogenic diet (keto-induction) can cause unpleasant symptoms, and this can reduce tolerability of the diet. Several methods have been suggested as useful for encouraging entry into nutritional ketosis (NK) and reducing symptoms of keto-induction. This paper reviews the scientific literature on the effects of these methods on time-to-NK and on symptoms during the keto-induction phase.

Methods

PubMed, Science Direct, CINAHL, MEDLINE, Alt Health Watch, Food Science Source and EBSCO Psychology and Behavioural Sciences Collection electronic databases were searched online. Various purported ketogenic supplements were searched along with the terms “ketogenic diet”, “ketogenic”, “ketosis” and ketonaemia (/ ketonemia). Additionally, author names and reference lists were used for further search of the selected papers for related references.

Results

Evidence, from one mouse study, suggests that leucine doesn’t significantly increase beta-hydroxybutyrate (BOHB) but the addition of leucine to a ketogenic diet in humans, while increasing the protein-to-fat ratio of the diet, doesn’t reduce ketosis. Animal studies indicate that the short chain fatty acids acetic acid and butyric acid, increase ketone body concentrations. However, only one study has been performed in humans. This demonstrated that butyric acid is more ketogenic than either leucine or an 8-chain monoglyceride. Medium-chain triglycerides (MCTs) increase BOHB in a linear, dose-dependent manner, and promote both ketonaemia and ketogenesis. Exogenous ketones promote ketonaemia but may inhibit ketogenesis.

Conclusions

There is a clear ketogenic effect of supplemental MCTs; however, it is unclear whether they independently improve time to NK and reduce symptoms of keto-induction. There is limited research on the potential for other supplements to improve time to NK and reduce symptoms of keto-induction. Few studies have specifically evaluated symptoms and adverse effects of a ketogenic diet during the induction phase. Those that have typically were not designed to evaluate these variables as primary outcomes, and thus, more research is required to elucidate the role that supplementation might play in encouraging ketogenesis, improve time to NK, and reduce symptoms associated with keto-induction.

Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults

With an ageing population, dietary approaches to promote health and independence later in life are needed. In part, this can be achieved by maintaining muscle mass and strength as people age. New evidence suggests that current dietary recommendations for protein intake may be insufficient to achieve this goal and that individuals might benefit by increasing their intake and frequency of consumption of high-quality protein. However, the environmental effects of increasing animal-protein production are a concern, and alternative, more sustainable protein sources should be considered. Protein is known to be more satiating than other macronutrients, and it is unclear whether diets high in plant proteins affect the appetite of older adults as they should be recommended for individuals at risk of malnutrition. The review considers the protein needs of an ageing population (>40 years old), sustainable protein sources, appetite-related implications of diets high in plant proteins, and related areas for future research.

Chronic Ketogenic Low Carbohydrate High Fat Diet Has Minimal Effects on Acid-Base Status in Elite Athletes

Although short (up to 3 days) exposure to major shifts in macronutrient intake appears to alter acid-base status, the effects of sustained (>1 week) interventions in elite athletes has not been determined. Using a non-randomized, parallel design, we examined the effect of adaptations to 21 days of a ketogenic low carbohydrate high fat (LCHF) or periodized carbohydrate (PCHO) diet on pre- and post-exercise blood pH, and concentrations of bicarbonate (HCO₃-) and lactate (La-) in comparison to a high carbohydrate (HCHO) control. Twenty-four (17 male and 7 female) elite-level race walkers completed 21 days of either LCHF (n = 9), PCHO (n = 7), or HCHO (n = 8) under controlled diet and training conditions. At baseline and post-intervention, blood pH, blood [HCO₃-], and blood [La-] were measured before and after a graded exercise test. Net endogenous acid production (NEAP) over the previous 48-72 h was also calculated from monitored dietary intake. LCHF was not associated with significant differences in blood pH, [HCO₃-], or [La-], compared with the HCHO diet pre- or post-exercise, despite a significantly higher NEAP (mEq·day-1) (95% CI = [10.44; 36.04]). Our results indicate that chronic dietary interventions are unlikely to influence acid-base status in elite athletes, which may be due to pre-existing training adaptations, such as an enhanced buffering capacity, or the actions of respiratory and renal pathways, which have a greater influence on regulation of acid-base status than nutritional intake.

A Ketone Ester Drink Lowers Human Ghrelin and Appetite

OBJECTIVE

The ketones d-β-hydroxybutyrate (BHB) and acetoacetate are elevated during prolonged fasting or during a "ketogenic" diet. Although weight loss on a ketogenic diet may be associated with decreased appetite and altered gut hormone levels, it is unknown whether such changes are caused by elevated blood ketones. This study investigated the effects of an exogenous ketone ester (KE) on appetite.

METHODS

Following an overnight fast, subjects with normal weight (n = 15) consumed 1.9 kcal/kg of KE, or isocaloric dextrose (DEXT), in drinks matched for volume, taste, tonicity, and color. Blood samples were analyzed for BHB, glucose, insulin, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide tyrosine tyrosine (PYY), and a three-measure visual analogue scale was used to measure hunger, fullness, and desire to eat.

RESULTS

KE consumption increased blood BHB levels from 0.2 to 3.3 mM after 60 minutes. DEXT consumption increased plasma glucose levels between 30 and 60 minutes. Postprandial plasma insulin, ghrelin, GLP-1, and PYY levels were significantly lower 2 to 4 hours after KE consumption, compared with DEXT consumption. Temporally related to the observed suppression of ghrelin, reported hunger and desire to eat were also significantly suppressed 1.5 hours after consumption of KE, compared with consumption of DEXT.

CONCLUSIONS

Increased blood ketone levels may directly suppress appetite, as KE drinks lowered plasma ghrelin levels, perceived hunger, and desire to eat.

A high carbohydrate, but not fat or protein meal attenuates postprandial ghrelin, PYY and GLP-1 responses in Chinese men

It is known that the macronutrient content of a meal has different impacts on the postprandial satiety and appetite hormonal responses. Whether obesity interacts with such nutrient-dependent responses is not well characterized. We examined the postprandial appetite and satiety hormonal responses after a high-protein (HP), high-carbohydrate (HC), or high-fat (HF) mixed meal. This was a randomized cross-over study of 9 lean insulin-sensitive (mean±SEM HOMA-IR 0.83±0.10) and 9 obese insulin-resistant (HOMA-IR 4.34±0.41) young (age 21–40 years), normoglycaemic Chinese men. We measured fasting and postprandial plasma concentration of glucose, insulin, active glucagon-like peptide-1 (GLP-1), total peptide-YY (PYY), and acyl-ghrelin in response to HP, HF, or HC meals. Overall postprandial plasma insulin response was more robust in the lean compared to obese subjects. The postprandial GLP-1 response after HF or HP meal was higher than HC meal in both lean and obese subjects. In obese subjects, HF meal induced higher response in postprandial PYY compared to HC meal. HP and HF meals also suppressed ghrelin greater compared to HC meal in the obese than lean subjects. In conclusion, a high-protein or high-fat meal induces a more favorable postprandial satiety and appetite hormonal response than a high-carbohydrate meal in obese insulin-resistant subjects.

Strategies to Improve Adherence to Dietary Weight Loss Interventions in Research and Real-World Settings

Dietary interventions are the cornerstone of obesity treatment. The optimal dietary approach to weight loss is a hotly debated topic among health professionals and the lay public alike. An emerging body of evidence suggests that a higher level of adherence to a diet, regardless of the type of diet, is an important factor in weight loss success over the short and long term. Key strategies to improve adherence include designing dietary weight loss interventions (such as ketogenic diets) that help to control the increased drive to eat that accompanies weight loss, tailoring dietary interventions to a person’s dietary preferences (and nutritional requirements), and promoting self-monitoring of food intake. The aim of this paper is to examine these strategies, which can be used to improve adherence and thereby increase the success of dietary weight loss interventions.

Effect of high-protein meal replacement on weight and cardiometabolic profile in overweight/obese Asian Indians in North India

The aim of the present study was to evaluate the impact of a high-protein meal replacement (HPMR) on weight and metabolic, lipid and inflammatory parameters in overweight/obese Asian Indians. In this 12-week open-label, parallel-arm randomised controlled trial, 122 overweight/obese men and women were administered either a HPMR or a control diet after 2 weeks of diet and exercise run-in. Body weight, waist circumference (WC), percentage body fat (%BF), fasting blood glucose, post-oral glucose tolerance test (post-OGTT) blood glucose, fasting and post-OGTT serum insulin, lipid profile, high-sensitivity C-reactive protein (hs-CRP), kidney function and hepatic aminotransferases were assessed before and after the intervention. Additional improvement in mean values for the following parameters in the HPMR group compared with the control group was observed: body weight, 4·9 % (95 % CI 3·8, 6·1; P<0·001); WC, 3·8 % (95 % CI 2·5, 5·1; P<0·001); %BF, 6·3 % (95 % CI 4·3, 8·2; P<0·001); systolic blood pressure, 2·8 % (95 % CI 0·4, 5·1; P=0·002); diastolic blood pressure, 3·5 % (95 % CI 0·7, 6·3; P= 0·01); post-OGTT blood glucose, 7·3 % (95 % CI 1·4, 13·1; P=0·02); total cholesterol, 2·5 % (95 % CI 1·6, 3·5; P<0·001); LDL-cholesterol, 7·3 % (95 % CI 1·7, 12·9; P<0·01); alanine aminotransferase, 22·0 % (95 % CI 2·1, 42; P=0·03) and aspartate aminotransferase, 15·2 % (95 % CI 0·9, 29·5; P=0·04). The absolute reduction in BMI was 0·9 units in the intervention arm compared with the control arm (-0·9 %, 95 % CI -1·4, -0·5; P<0·001) and in serum TAG was 11·9 mg/dl (-11·9 mg/dl, 95 % CI -21·1, -2·7; P<0·01). The reduction in fasting serum insulin in the intervention v. the control arm was 3·8 v. 0 % (P=0·002); post-OGTT serum insulin was 50·3 v. 77·3 mU/l (P=0·005); and hs-CRP, 16·7 % v. 0 % (P=0·002). These findings show that intervention with HPMR may lead to significant weight loss and improvement in obesity measures, metabolic, lipid and inflammatory parameters and hepatic transaminases in overweight/obese Asian Indians.

International society of sports nutrition position stand: diets and body composition

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of diet types (macronutrient composition; eating styles) and their influence on body composition. The ISSN has concluded the following. 1) There is a multitude of diet types and eating styles, whereby numerous subtypes fall under each major dietary archetype. 2) All body composition assessment methods have strengths and limitations. 3) Diets primarily focused on fat loss are driven by a sustained caloric deficit. The higher the baseline body fat level, the more aggressively the caloric deficit may be imposed. Slower rates of weight loss can better preserve lean mass (LM) in leaner subjects. 4) Diets focused primarily on accruing LM are driven by a sustained caloric surplus to facilitate anabolic processes and support increasing resistance-training demands. The composition and magnitude of the surplus, as well as training status of the subjects can influence the nature of the gains. 5) A wide range of dietary approaches (low-fat to low-carbohydrate/ketogenic, and all points between) can be similarly effective for improving body composition. 6) Increasing dietary protein to levels significantly beyond current recommendations for athletic populations may result in improved body composition. Higher protein intakes (2.3–3.1 g/kg FFM) may be required to maximize muscle retention in lean, resistance-trained subjects under hypocaloric conditions. Emerging research on very high protein intakes (>3 g/kg) has demonstrated that the known thermic, satiating, and LM-preserving effects of dietary protein might be amplified in resistance-training subjects. 7) The collective body of intermittent caloric restriction research demonstrates no significant advantage over daily caloric restriction for improving body composition. 8) The long-term success of a diet depends upon compliance and suppression or circumvention of mitigating factors such as adaptive thermogenesis. 9) There is a paucity of research on women and older populations, as well as a wide range of untapped permutations of feeding frequency and macronutrient distribution at various energetic balances combined with training. Behavioral and lifestyle modification strategies are still poorly researched areas of weight management.

Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies

The treatment of obesity and cardiovascular diseases is one of the most difficult and important challenges nowadays. Weight loss is frequently offered as a therapy and is aimed at improving some of the components of the metabolic syndrome. Among various diets, ketogenic diets, which are very low in carbohydrates and usually high in fats and/or proteins, have gained in popularity. Results regarding the impact of such diets on cardiovascular risk factors are controversial, both in animals and humans, but some improvements notably in obesity and type 2 diabetes have been described. Unfortunately, these effects seem to be limited in time. Moreover, these diets are not totally safe and can be associated with some adverse events. Notably, in rodents, development of nonalcoholic fatty liver disease (NAFLD) and insulin resistance have been described. The aim of this review is to discuss the role of ketogenic diets on different cardiovascular risk factors in both animals and humans based on available evidence.

Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review

Low-carbohydrate high-fat (LCHF) diets are a highly contentious current topic in nutrition. This narrative review aims to provide clinicians with a broad overview of the effects of LCHF diets on body weight, glycaemic control and cardiovascular risk factors while addressing some common concerns and misconceptions. Blood total cholesterol and LDL-cholesterol concentrations show a variable, highly individual response to LCHF diets, and should be monitored in patients adhering to this diet. In contrast, available evidence from clinical and preclinical studies indicates that LCHF diets consistently improve all other markers of cardiovascular risk-lowering elevated blood glucose, insulin, triglyceride, ApoB and saturated fat (especially palmitoleic acid) concentrations, reducing small dense LDL particle numbers, glycated haemoglobin (HbA_1c) levels, blood pressure and body weight while increasing low HDL-cholesterol concentrations and reversing non-alcoholic fatty liver disease (NAFLD). This particular combination of favourable modifications to all these risk factors is a benefit unique to LCHF diets. These effects are likely due in part to reduced hunger and decreased ad libitum calorie intake common to low-carbohydrate diets, allied to a reduction in hyperinsulinaemia, and reversal of NAFLD. Although LCHF diets may not be suitable for everyone, available evidence shows this eating plan to be a safe and efficacious dietary option to be considered. LCHF diets may also be particularly beneficial in patients with atherogenic dyslipidaemia, insulin resistance, and the frequently associated NAFLD.

A Nutritional Perspective of Ketogenic Diet in Cancer: A Narrative Review

The predominant use of glucose anaerobically by cancer cells (Warburg effect) may be the most important characteristic the majority of these cells have in common and, therefore, a potential metabolic pathway to be targeted during cancer treatment. Because this effect relates to fuel oxidation, dietary manipulation has been hypothesized as an important strategy during cancer treatment. As such, the concept of a ketogenic diet (KD) in cancer emerged as a metabolic therapy (ie, targeting cancer cell metabolism) rather than a dietary approach. The therapeutic mechanisms of action of this high-fat, moderate-to-low protein, and very-low-carbohydrate diet may potentially influence cancer treatment and prognosis. Considering the lack of a dietetics-focused narrative review on this topic, we compiled the evidence related to the use of this diet in humans with diverse cancer types and stages, also focusing on the nutrition and health perspective. The use of KD in cancer shows potentially promising, but inconsistent, results. The limited number of studies and differences in study design and characteristics contribute to overall poor quality evidence, limiting the ability to draw evidence-based conclusions. However, the potential positive influences a KD may have on cancer treatment justify the need for well-designed clinical trials to better elucidate the mechanisms by which this dietary approach affects nutritional status, cancer prognosis, and overall health. The role of registered dietitian nutritionists is demonstrated to be crucial in planning and implementing KD protocols in oncology research settings, while also ensuring patients' adherence and optimal nutritional status.

Differential effects of L-tryptophan and L-leucine administration on brain resting state functional networks and plasma hormone levels

Depending on their protein content, single meals can rapidly influence the uptake of amino acids into the brain and thereby modify brain functions. The current study investigates the effects of two different amino acids on the human gut-brain system, using a multimodal approach, integrating physiological and neuroimaging data. In a randomized, placebo-controlled trial, L-tryptophan, L-leucine, glucose and water were administered directly into the gut of 20 healthy subjects. Functional MRI (fMRI) in a resting state paradigm (RS), combined with the assessment of insulin and glucose blood concentration, was performed before and after treatment. Independent component analysis with dual regression technique was applied to RS-fMRI data. Results were corrected for multiple comparisons. In comparison to glucose and water, L-tryptophan consistently modifies the connectivity of the cingulate cortex in the default mode network, of the insula in the saliency network and of the sensory cortex in the somatosensory network. L-leucine has lesser effects on these functional networks. L-tryptophan and L-leucine also modified plasma insulin concentration. Finally, significant correlations were found between brain modifications after L-tryptophan administration and insulin plasma levels. This study shows that acute L-tryptophan and L-leucine intake directly influence the brain networks underpinning the food-reward system and appetite regulation.

Hypothalamic sensing of ketone bodies after prolonged cerebral exposure leads to metabolic control dysregulation

Ketone bodies have been shown to transiently stimulate food intake and modify energy homeostasis regulatory systems following cerebral infusion for a moderate period of time (<6 hours). As ketone bodies are usually enhanced during episodes of fasting, this effect might correspond to a physiological regulation. In contrast, ketone bodies levels remain elevated for prolonged periods during obesity, and thus could play an important role in the development of this pathology. In order to understand this transition, ketone bodies were infused through a catheter inserted in the carotid to directly stimulate the brain for a period of 24 hours. Food ingested and blood circulating parameters involved in metabolic control as well as glucose homeostasis were determined. Results show that ketone bodies infusion for 24 hours increased food intake associated with a stimulation of hypothalamic orexigenic neuropeptides. Moreover, insulinemia was increased and caused a decrease in glucose production despite an increased resistance to insulin. The present study confirms that ketone bodies reaching the brain stimulates food intake. Moreover, we provide evidence that a prolonged hyperketonemia leads to a dysregulation of energy homeostasis control mechanisms. Finally, this study shows that brain exposure to ketone bodies alters insulin signaling and consequently glucose homeostasis.

Combined effects of resistance training and carbohydrate-restrictive or conventional diets on weight loss, blood variables and endothelium function

ABSTRACT Objective: To compare the effects of either a carbohydrate-restrictive diets or a conventional hypoenergetic diet combined with resistance training. Methods: Twenty-one overweight and obese adults participated in an eight-week program consisting of progressive resistance training combined with carbohydrate-restrictive diets (initially set at <30 g carbohydrate; n=12) or conventional hypoenergetic diet (30% energetic restriction; carbohydrate/protein/lipid: 51/18/31% of total energy consumption; n=9). It was hypothesized that the carbohydrate-restrictive diets would induce greater weight loss but that both diets would elicit similar effects on selected health markers. Body mass, and body composition, blood variables and flow-mediated brachial artery dilation (flow-mediated brachial artery dilation; by ultrasound) were used to assess changes due to the interventions. Results: Significant within-group reductions in body mass (-5.4±3.5%; p=0.001 versus -3.7±3.0%; p=0.015) and body fat (body fat; -10.2±7.0%; p=0.005 versus -9.6±8.8%; p=0.017) were identified for carbohydrate-restrictive diets and conventional hypoenergetic diet, respectively, but there were no significant differences between groups as the result of the interventions. Fat free mass, blood variables and flow-mediated brachial artery dilation did not significantly change, except for the total cholesterol/high-density lipoprotein ratio, which was reduced 10.4±16.9% in carbohydrate-restrictive diets (p=0.037) and 0.5±11.3% in conventional hypoenergetic diet (p=0.398). Conclusion: Carbohydrate-restrictive diets associated with resistance training was as effective as conventional hypoenergetic diet in decreasing body mass and body fat, as well as maintaining fat free mass, blood variables and flow-mediated brachial artery dilation, however it was more effective at lowering the total cholesterol/low density lipoprotein ratio.

The effects of a low-carbohydrate diet on appetite: A randomized controlled trial

BACKGROUND AND AIMS

The relationship between dietary macronutrient composition and appetite is controversial. We examined the effects of a year-long low-carbohydrate diet compared to a low-fat diet on appetite-related hormones and self-reported change in appetite.

METHODS AND RESULTS

A total of 148 adults with a body mass index 30-45 kg/m(2), who were free of diabetes, cardiovascular disease and chronic kidney disease at baseline were randomly assigned to either a low-carbohydrate diet (carbohydrate [excluding dietary fiber]<40 g/day; N = 75) or a low-fat diet (<30% energy from fat, <7% from saturated fat; N = 73). Participants in both groups attended individual and group dietary counseling sessions where they were provided the same behavioral curriculum and advised to maintain baseline levels of physical activity. Appetite and appetite-related hormones were measured at 0, 3, 6 and 12 months of intervention. At 12 months, mean changes (95% CI) in peptide YY were -34.8 pg/mL (-41.0 to -28.6) and in the low-carbohydrate group and -44.2 pg/mL (-50.4 to -38.0) in the low-fat group (net change: 9.54 pg/mL [0.6 to 18.2]; p = 0.036). Approximately 99% of dietary effects on peptide YY are explained by differences in dietary macronutrient content. There was no difference in change in ghrelin or self-reported change in appetite between the groups.

CONCLUSIONS

A low-fat diet reduced peptide YY more than a low-carbohydrate diet. These findings suggest that satiety may be better preserved on a low-carbohydrate diet, as compared to a low fat diet.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00609271.

Changes of Mouse Gut Microbiota Diversity and Composition by Modulating Dietary Protein and Carbohydrate Contents: A Pilot Study

Dietary proteins influence colorectal cancer (CRC) risk, depending on their quantity and quality. Here, using pyrosequencing, we compared the fecal microbiota composition in Balb/c mice fed either a normal protein/carbohydrate diet (ND, 20% casein and 68% carbohydrate) or a high-protein/low-carbohydrate diet (HPLCD, 30% casein and 57% carbohydrate). The results showed that HPLCD feeding for 2 weeks reduced the diversity and altered the composition of the microbiota compared with the ND mice, which included a decrease in the proportion of the family Lachnospiraceae and Ruminococcaceae and increases in the proportions of the genus Bacteroides and Parabacteroides, especially the species EF09600_s and EF604598_s. Similar changes were reported in patients with inflammatory bowel disease, and in mouse models of CRC and colitis, respectively. This suggests that HPLCD may lead to a deleterious luminal environment and may have adverse effects on the intestinal health of individuals consuming such a diet.

High Leucine Diets Stimulate Cerebral Branched-Chain Amino Acid Degradation and Modify Serotonin and Ketone Body Concentrations in a Pig Model

In addition to its role as an essential protein component, leucine (Leu) displays several other metabolic functions such as activation of protein synthesis. This property makes it an interesting amino acid for the therapy of human muscle atrophy and for livestock production. However, Leu can stimulate its own degradation via the branched-chain keto acid dehydrogenase complex (BCKDH). To examine the response of several tissues to excessive Leu, pigs were fed diets containing two- (L2) and four-fold (L4) higher Leu contents than the recommended amount (control). We found that the L4 diet led to a pronounced increase in BCKDH activity in the brain (2.5-fold, P < 0.05), liver (1.8-fold, P < 0.05) and cardiac muscle (1.7-fold, P < 0.05), whereas we found no changes in enzyme activity in the pancreas, skeletal muscle, adipose tissue and intestinal mucosa. The L2 diet had only weak effects on BCKDH activity. Both high Leu diets reduced the concentrations of free valine and isoleucine in nearly all tissues. In the brain, high Leu diets modified the amount of tryptophan available: for serotonin synthesis. Compared to the controls, pigs treated with the high Leu diets consumed less food, showed increased plasma concentrations of 3-hydroxybutyrate and reduced levels of circulating serotonin. In conclusion, excessive Leu can stimulate BCKDH activity in several tissues, including the brain. Changes in cerebral tryptophan, along with the changes in amino acid-derived metabolites in the plasma may limit the use of high Leu diets to treat muscle atrophy or to increase muscle growth.

Energy-restricted, high-protein diets more effectively impact cardiometabolic profile in overweight and obese women than lower-protein diets

BACKGROUND & AIMS

High-protein energy-restricted diets have demonstrated efficacy in promoting weight loss in overweight and obesity. However, the protein percentage that achieves optimal efficacy and acceptability remains unknown. We sought to assess the effects of three energy-reduced diets with different percentages of calories from protein (20%, 27%, and 35%) on weight loss and lipids. Secondary outcomes included diet acceptability and compliance.

METHODS

Six-month, randomized study included women aged 18-80 years with BMI of 27.5-45 kg/m² and who were not taking lipid-lowering drugs. We randomly assigned 91 women to one of three calorie-reduced diets with: protein, 20%, 27%, or 35% (80% from animal protein); carbohydrates, 50%, 43%, or 35%; fat, 30%. Dietary intervention involved individual visits with a nutritionist every 2 weeks during the first 3 months. We performed a follow-up visit at 6 months.

RESULTS

Eighty women aged 44.0 ± 9.08 years with BMI of 37.7 ± 3.39 kg/m² completed the study. At 3 months, weight loss was -8.16 ± 4.18 kg, -9.66 ± 5.28 kg, and -10.7 ± 4.28 kg in the 20%, 27%, and 35%-protein groups, respectively (P = 0.16). These figures slightly and homogeneously increased at 6 months. Around 65% of women following 35%-protein diet lost ≥10% of body weight vs. ∼33% in 20%-protein group (P = 0.023). Significant decreases occurred in fat mass, lipids and insulin resistance, especially in the 35%-protein group (P < 0.05 vs. 20% protein). This improvement was not fully explained by weight loss. Triglyceride change was negatively correlated with animal-protein intake. All groups provided similar responses to an acceptance, palatability, and satisfaction questionnaire.

CONCLUSIONS

An energy-restricted diet with 35% protein, mostly of animal origin, more effectively impacts cardiometabolic profile than an energy-restricted diet with lower protein content although no clear benefit between diets in terms of overall weight loss was observed. The high-protein diet displayed an excellent safety profile and acceptability. This trial was registered in ClinicalTrials.gov as NCT02160496.

CLINICAL TRIAL REGISTRATION

The clinical trial has been registered in ClinicalTrials.gov (Identifier: NCT02160496).

Evidence for hypothalamic ketone body sensing: impact on food intake and peripheral metabolic responses in mice

Monocarboxylates have been implicated in the control of energy homeostasis. Among them, the putative role of ketone bodies produced notably during high-fat diet (HFD) has not been thoroughly explored. In this study, we aimed to determine the impact of a specific rise in cerebral ketone bodies on food intake and energy homeostasis regulation. A carotid infusion of ketone bodies was performed on mice to stimulate sensitive brain areas for 6 or 12 h. At each time point, food intake and different markers of energy homeostasis were analyzed to reveal the consequences of cerebral increase in ketone body level detection. First, an increase in food intake appeared over a 12-h period of brain ketone body perfusion. This stimulated food intake was associated with an increased expression of the hypothalamic neuropeptides NPY and AgRP as well as phosphorylated AMPK and is due to ketone bodies sensed by the brain, as blood ketone body levels did not change at that time. In parallel, gluconeogenesis and insulin sensitivity were transiently altered. Indeed, a dysregulation of glucose production and insulin secretion was observed after 6 h of ketone body perfusion, which reversed to normal at 12 h of perfusion. Altogether, these results suggest that an increase in brain ketone body concentration leads to hyperphagia and a transient perturbation of peripheral metabolic homeostasis.

Food science and food ingredients: the need for reliable scientific approaches and correct communication, Florence, 24 March 2015

This report summarises the proceedings of a conference organised by the Italian Association of Hospital Cardiologists. The aim was to consider the process by which dietary guidelines (DG) are developed and the quality of evidence underpinning these guidelines, as well as debating whether or not this has resulted in DG that are effective in terms of health improvement. Key points were a caution about false positives in research, the importance of holistic DG rather than single nutrient targets, the need for appropriate disease endpoints in studies and control of confounders, a plea for less reliance on observational studies which cannot address cause-and-effect relationships and a need to bear in mind unintended consequences. Options for improving the system and the quality of evidence were discussed.

Fish oil supplemented for 9 months does not improve glycaemic control or insulin sensitivity in subjects with impaired glucose regulation: a parallel randomised controlled trial

The effects of fish oil (FO) supplementation on glycaemic control are unclear, and positive effects may occur only when the phospholipid content of tissue membranes exceeds 14 % asn-3 PUFA. Subjects (n36, thirty-three completed) were paired based on metabolic parameters and allocated into a parallel double-blind randomised trial with one of each pair offered daily either 6 g of FO (3·9 gn-3 PUFA) or 6 g of maize oil (MO) for 9 months. Hyperinsulinaemic–euglycaemic–euaminoacidaemic (HIEGEAA) clamps (with [6,62H2glucose]) were performed at the start and end of the intervention. Endogenous glucose production (EGP) and whole-body protein turnover (WBPT) were each measured after an overnight fast. The primary outcome involved the effect of oil type on insulin sensitivity related to glycaemic control. The secondary outcome involved the effect of oil type on WBPT. Subjects on FO (n16) had increased erythrocyten-3 PUFA concentrations >14 %, whereas subjects on MO (n17) had unalteredn-3 PUFA concentrations at 9 %. Type of oil had no effect on fasting EGP, insulin sensitivity or total glucose disposal during the HIEGEAA clamp. In contrast, under insulin-stimulated conditions, total protein disposal (P=0·007) and endogenous WBPT (P=0·001) were both increased with FO. In an associated pilot study (n4, three completed), althoughn-3 PUFA in erythrocyte membranes increased to >14 % with the FO supplement, the enrichment in muscle membranes remained lower (8 %;P<0·001). In conclusion, long-term supplementation with FO, at amounts near the safety limits set by regulatory authorities in Europe and the USA, did not alter glycaemic control but did have an impact on WBPT.

Prevention of type 2 diabetes through lifestyle modification: is there a role for higher-protein diets?

Type 2 diabetes (T2D) incidence is increasing worldwide, driven by a rapidly changing environment and lifestyle and increasing rates of overweight and obesity. Prevention of diabetes is key and is most likely achieved through prevention of weight gain and/or successful long-term weight loss maintenance. Weight loss is readily achievable but there is considerable challenge in maintaining that weight loss over the long term. Lower-fat carbohydrate-based diets are widely used for T2D prevention. This is supported primarily by 3 successful long-term interventions, the US Diabetes Prevention Program, the Finnish Diabetes Prevention Study, and the Chinese Da Qing Study, but evidence is building in support of novel higher-protein (>20% of energy) diets for successful weight loss maintenance and prevention of T2D. Higher-protein diets have the advantage of having relatively low energy density, aiding longer-term appetite suppression, and preserving lean body mass, all central to successful weight loss and prevention of weight regain. Here, we review the carbohydrate-based intervention trials and present mechanistic evidence in support of increased dietary protein for weight loss maintenance and a possible novel role in prevention of dysglycemia and T2D.