Influence of dietary fat polyunsaturated to saturated ratio on energy substrate utilization in obesity

Comparing acute effects of extra virgin coconut oil and extra virgin olive oil consumption on appetite and food intake in normal-weight and obese male subjects

Objectives

The aim of this study is to compare acute effects of consuming extra virgin coconut oil (EVCO) as a source of medium chain fatty acids and extra virgin olive oil (EVOO) as a source of long chain fatty acids in normal weight and obese subjects.

Design

Randomised, crossover design.

Participants

Metabolically healthy twenty male subjects (10 normal weight; 10 obese) aged 19–40 years.

Intervention

Subjects consumed breakfast meals containing skimmed milk, fat-free white cheese, bread and EVCO (25 g) or EVOO (25 g).

Outcome measures

Visual analog scale evaluations, resting metabolic rate measurements and selected blood parameters analysis (glucose, triglyceride, insulin and plasma peptide YY) were performed before and after the test breakfast meals. In addition, energy intakes were evaluated by ad libitum lunch meal at 180 min.

Results

Visual analogue scale values of hunger and desire to eat decreased significantly after EVCO consumption than EVOO consumption in normal weight subjects at 180 min. There was an increase trend in plasma PYY at 30 and 180 min after EVCO breakfast compared to EVOO breakfast. Ad libitum energy intakes after EVCO and EVOO consumption in normal weight subjects were 924 ± 302; 845 ± 158 kcal (p = 0.272), respectively whereas in obese subjects were 859 ± 238; 994 ± 265 kcal (p = 0.069) respectively.

Conclusion

The results of this study shows that consumption of EVCO compared to EVOO may have suppressive effect on hunger and desire to eat, may affect postprandial PYY levels differently and have no effect on postprandial energy expenditure.

Trial registration

Clinical Trials NCT04738929.

Metabolic Responses to Eight Weeks of Consuming Cottonseed Oil v. Olive Oil in Adults with Dyslipidemia, a Randomized Trial

BACKGROUND

Differences in metabolic responses between diets rich in monounsaturated (MUFA) and polyunsaturated fats (PUFA) could affect energy balance and weight maintenance. The present study was a secondary analysis to investigate 8-week diet interventions rich in either PUFA (cottonseed oil (CSO)) or MUFA (olive oil (OO)) on metabolic responses in adults with dyslipidemia.

METHODS

Forty-one adults with dyslipidemia completed this randomized trial consisting of an 8-week partial-outpatient feeding trial. Provided foods accounted for ~60% of their daily energy needs, with ~30% of energy needs provided by CSO (n=20) or OO (n=21). At pre- and post-diet intervention visits, participants consumed a high saturated fat (SFA) meal (35% daily energy needs, 47.9% from SFA), and fasting and 3.5h postprandial indirect calorimetry was used to measure energy expenditure (EE) and substrate oxidation.

RESULTS

No changes were observed in fasting measures. The OO group had greater increases in postprandial EE (p=0.002); however, there were no differences in substrate oxidation between groups. A lack of metabolic flexibility was found in both groups, which was partially explained by changes in insulin sensitivity (homeostasis model assessment of insulin resistance (HOMA-IR)).

CONCLUSIONS

The results of the present study show OO, but not CSO, diet enrichment improves EE following the occasional high SFA meal, which may improve weight maintenance over time. Registered at clinicaltrials.gov (NCT04397055). This article is protected by copyright. All rights reserved.

Pecan-enriched diets increase energy expenditure and fat oxidation in adults at-risk for cardiovascular disease in a randomised, controlled trial

BACKGROUND

Research indicates that diets enriched with unsaturated fatty acids improve energy metabolism, although studies on tree nuts, which are a rich source of those fats, are limited. The present study aimed to examine the impact of daily pecan consumption for 8 weeks on energy metabolism in adults with hypercholesterolaemia or at higher risk for cardiovascular disease (CVD) (body mass index ≥ 28 kg m^-2 ).

METHODS

For this randomised, controlled trial, 56 sedentary adults were randomised into one of three treatments for an 8-week intervention: two pecan groups and a nut-free control group (n = 18). The ADD group (n = 16) consumed pecans as part of a free-living diet, whereas the SUB group (n = 18) substituted the pecans for isocaloric foods from their habitual diet. At baseline and 8 weeks, a high saturated fat meal was consumed along with indirect calorimetry measurements at fasting and for 4 h postprandially to determine changes in resting metabolic rate (RMR), diet induced thermogenesis (DIT) and substrate utilisation (primary outcomes). Forty-seven participants completed the trial and were included in analyses.

RESULTS

In the SUB group, there was an increase in fasting RMR (1607 ± 117 to 1701 ± 114 kcal day^-1 ; p = 0.01) and fasting fat oxidation (0.83 ± 0.08 to 0.99 ± 0.08 g/15 min; p = 0.009) and a decrease in fasting respiratory exchange ratio (0.85 ± 0.01 to 0.83 ± 0.01; p = 0.05) from pre- to post-intervention. In the ADD group, there was an increase in postprandial DIT (p < 0.001). There were no changes within the control group or between groups for any outcome measure.

CONCLUSIONS

Daily consumption of pecans may increase select measures of energy expenditure and fat oxidation in adults at-risk for CVD.

Adherence to the Mediterranean diet and body composition of breast-feeding mothers: the potential role of unsaturated fatty acids

A paucity of evidence is available regarding the impact of diet's quality during pregnancy and lactation on the body composition of breast-feeding mothers. The purpose of the present study was to evaluate the association between maternal degree of adherence to the Mediterranean diet (MD) and body composition measures specifically those relating to body fat, in the lactation period. A cross-sectional study on healthy mothers of full-term babies has been conducted. At 30 ± 10 d after delivery, anthropometric measurements and body composition were assessed. A food frequency questionnaire was performed to compute the Italian Mediterranean Index (IMI) score as an index of adherence to the MD. Data related to pregnancy such as pre-pregnancy weight, gestational weight gain and morbidities were also collected. The 147 mothers included were categorised in IMI-1 (IMI score < 5; n 92) and IMI-2 (IMI score ≥ 5; n 55) groups. IMI-2 mothers showed higher daily energy, total carbohydrates, starch and fibre intakes than IMI-1. The dietary habits of IMI-2 mothers reflect the typical characteristics of MD: they consumed higher quantities of proteins and lipids of vegetal origin, higher amounts of monounsaturated and polyunsaturated fatty acids (PUFAs) and lower saturated to PUFAs ratio. The IMI-2 group showed lower absolute fat mass and fat mass index compared to IMI-1 [(20⋅2 ± 5⋅9) v. (22⋅9 ± 8⋅4) kg; P 0⋅036 and (7⋅5 ± 2⋅2) v. (8⋅5 ± 3⋅1) kg/m²; P 0⋅036, respectively], whereas body weight [(61⋅1 ± 8⋅0) v. (63⋅3 ± 9⋅2) kg] and body mass index [(22⋅4 ± 2⋅6) v. (23⋅3 ± 3⋅5) kg/m²] were similar. The degree of adherence to the MD during pregnancy and lactation is positively associated with lower maternal fat deposition in the breast-feeding period. The higher quality of dietary lipids, probably in synergy with the assumption of starchy carbohydrates and fibre, could influence maternal body fat.

The effect of extra virgin olive oil on anthropometric indices, lipid profile, and markers of oxidative stress and inflammation in patients with depression, a double-blind randomised controlled trial

BACKGROUND

Epidemiological evidence suggests a mutual association between depression and obesity and also an anti-obesity effect for olive oil. We examined the effect of extra virgin olive oil (EVOO) on weight, waist circumference, and a number of cardiovascular risk factors in patients with depression.

METHODS

The randomised double-blind controlled trial was conducted on 62 patients with depression. Patients were randomly allocated to EVOO and sunflower oil groups (n = 31 for each) that consumed 25 mL/day of the corresponding oils for 52 days. An isocaloric diet was prescribed to each patient according to his/her previous energy intake with considering the energy provided by the administered oils. Weight, body mass index (BMI), waist circumference, blood lipids, malondialdehyde, and hs-C reactive protein (CRP) analysis were performed using the intention-to-treat approach.

RESULTS

BMI was significantly decreased in sunflower oil group (-0.20 ± 0.53 kg/m² , P = .047) and waist circumference was significantly decreased in EVOO group (-2.15 ± 2.09 cm, P < .001); however, only reduction of waist circumference was significantly different between groups (P < .001). High-density lipoprotein (HDL) cholesterol was significantly increased in EVOO group (3.02 ± 6.79 mg/dL, P = .03), without showing a significant between-group difference. Other lipids, malondialdehyde, and hs-CRP did not change.

CONCLUSION

Overall, the results suggest that both EVOO and sunflower oil may benefit overweight patients with depression, as they respectively decreased waist circumference and BMI without need for administration of a low-calorie diet.

Polyunsaturated fatty acids as modulators of fat mass and lean mass in human body composition regulation and cardiometabolic health

It is now recognized that the amount and type of dietary fat consumed play an important role in metabolic health. In humans, high intake of polyunsaturated fatty acids (PUFAs) has been associated with reductions in cardiovascular disease risk, improvements in glucose homeostasis, and changes in body composition that involve reductions in central adiposity and, more recently, increases in lean body mass. There is also emerging evidence, which suggests that high intakes of the plant-based essential fatty acids (ePUFAs)-n-6 linoleic acid (LA) and n-3 α-linolenic acid (ALA)-have a greater impact on body composition (fat mass and lean mass) and on glucose homeostasis than the marine-derived long-chain n-3 PUFA-eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In addition, high intake of both ePUFAs (LA and ALA) may also have anti-inflammatory effects in humans. The purpose of this review is to highlight the emerging evidence, from both epidemiological prospective studies and clinical intervention trials, of a role for PUFA, in particular ePUFA, in the long-term regulation of body weight and body composition, and their impact on cardiometabolic health. It also discusses current notions about the mechanisms by which PUFAs modulate fat mass and lean mass through altered control of energy intake, thermogenesis, or lean-fat partitioning.

A review on differential effects of dietary fatty acids on weight, appetite and energy expenditure

The association between weight and chronic diseases is well defined. The quality and quantity of dietary fatty acids is an important external factor and appetite and energy expenditure, are important internal factors in determining body weight. On the other hand, dietary fatty acids composition can modulate appetite and energy metabolism, but not all fats are equal in producing metabolic responses.Given the accumulating evidence for differential effects of various dietary fatty acids, one important area of investigation is to scrutinize their roles in weight, appetite and energy expenditure modulation. There is substantial evidence to suggest that saturated fatty acids have a greater effect on appetite control, although in the long run may result in more weight gain than unsaturated fatty acids due to a weaker stimulation of energy expenditure. In contrast, mono-unsaturated fats do not have much effects on appetite control, but they can be beneficial in weight control over the long term due to stimulatory effects on energy expenditure. Interestingly, in case of poly unsaturated fats, including n-3 and n-6, their effect on increasing energy expenditure is aligned, but they act differently in controlling weight and appetite.

Body composition, not dietary fatty acid composition, explains metabolic responses following a high-fat meal in premenopausal normal-weight women: a single-blind, randomised, crossover study

The aim of this study was to examine the effect of three different fatty acid (FA)-rich meals enriched in either SFA, MUFA or PUFA on postprandial metabolic responses in premenopausal, normal-weight women. For this randomised, single-blind, crossover study, three high-fat (HF) meals rich in either SFA, MUFA or PUFA (65 % energy from fat; 35 % of participants’ total daily energy needs) were tested. For each visit, anthropometrics and RMR were measured following a 12–15 h fast. Then, participants consumed one of the HF meals, and respiratory gases were collected using indirect calorimetry for 3 h postprandially. Energy expenditure (EE) following a SFA-rich meal was significantly higher than a MUFA-rich meal (P = 0·04; η2 = 0·19), but SFA was not significantly different from PUFA. There was a trend towards significance in EE between PUFA and MUFA (P = 0·06). After adjusting for fat-free mass (FFM), there were no longer condition or time effects for EE, although FFM remained a significant predictor (P = 0·005; η2 = 0·45). There were no significant differences between conditions for dietary-induced thermogenesis or substrate oxidation. The relationship between fat mass (FM) and both total fat oxidation (r 0·62; P = 0·025) and total change in RER following a MUFA-rich meal was observed (r −0·55; P = 0·05). In conclusion, weight loss through increases in EE may be best achieved by increasing FFM rather than selection of FA type. Further, a relationship exists between FM and fat oxidation following a MUFA-rich meal, most likely due to an unidentified mechanism.

Effects of sweet almond (Prunus amygdalus) suspension on blood biochemical parameters in experimentally induced hyperlipidemic mice

Aim:

The present study aimed to examine the effects of sweet almond (Prunus amygdalus) suspension (SAS) on the measurements of blood biochemical parameters in male albino mice, in which hyperlipidemia was induced experimentally.

Materials and Methods:

Seventy male albino mice were divided randomly into seven groups (10 mice/group). The first group was the untreated control group (negative control). The second group comprised hyperlipidemic mice that did not receive SAS treatment (positive control). The other five groups consisted of hyperlipidemic mice that were orally administered five different doses of SAS (285, 571, 857, 1128, and 1428 mg/kg body weight). Hyperlipidemia was induced in mice by adding 1% cholesterol to the diet along with 0.5% H₂O₂ to the drinking water, with ad libitum access to both food and water for 60 consecutive days. Prothrombin time, partial thromboplastin time, clotting time, and platelet count were measured. Serum lipid profile (total cholesterol [TC], triacylglycerol [TAG], low-density lipoprotein cholesterol [LDL-C], very LDL-C [VLDL-C], and high-density lipoprotein cholesterol [HDL-C]) was also determined.

Results:

Prothrombin time, partial thromboplastin time, and clotting time significantly increased only in groups treated with SAS, especially at the dosage of 1428 mg/kg compared with the positive control group. Blood platelet count significantly decreased in SAS-treated groups. The serum levels of TC, TAG, LDL-C, and VLDL-C in the SAS-treated groups (857, 1128, and 1428 mg/kg) significantly decreased, whereas the serum level of HDL-C significantly increased compared with that of the positive control group.

Conclusion:

SAS administered orally at 1428 mg/kg body weight was the dose that most significantly decreased platelet count and serum levels of TC, TAG, LDL-C, and VLDL-C and increased prothrombin time, partial thromboplastin time, and clotting time as well as serum level of HDL-C in experimentally induced hyperlipidemic mice.

Differential Effects of Monounsaturated and Polyunsaturated Fats on Satiety and Gut Hormone Responses in Healthy Subjects

The difference between fat saturation on postprandial hormone responses and acute appetite control is not well understood. The aim of this study was to compare the postprandial ghrelin, gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP1) response and subjective appetite responses after isoenergetic high-fat meals rich in either monounsaturated (MUFAs) or polyunsaturated fatty acids (PUFAs) in healthy Chinese males. A randomized, controlled, single-blinded crossover study was conducted in 13 healthy Chinese men. Two high-fat meals (64% of energy) rich in MUFAs or PUFAs were tested. Total ghrelin, GIP and active GLP1 and visual analog scale (VAS) were measured over 4 h. Ghrelin was reduced greater after MUFA compared to PUFA at the beginning of the meal (at 30 and 60 min) and was significantly negatively correlated with subjective VAS for preoccupation for both MUFA and PUFA meals. No significant difference for ghrelin 240 min incremental area under the curve (iAUCs) were found. MUFA induced higher GIP response than PUFA. GIP was associated with all the VAS measurements except preoccupation for MUFA meal. No difference was found for GLP1 between two meals, nor was GLP1 associated with VAS. In conclusion, the results demonstrate that ghrelin, GIP and VAS respond differently to MUFA and PUFA meals. Ghrelin and GIP, but not GLP1, were associated with acute appetite control, especially after MUFA meal.

The Effect of Canola Oil on Body Weight and Composition: A Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials

A number of clinical trials have examined the effect of canola oil (CO) on body composition in recent years; however, the results have been inconsistent. The present investigation aims to examine the effect of CO on body weight (BW) and body composition using a systematic review and meta-analysis of controlled clinical trials. Online databases including PubMed, Scopus, and Google Scholar were searched up to February, 2018 for randomized controlled clinical trials that examined the effect of CO on anthropometric measures and body composition indexes in adults. The Cochrane Collaboration's tool was used to assess the risk of bias in individual studies. A random-effects model was used to evaluate the effect of CO consumption on several outcomes: BW, body mass index, waist circumference, hip circumference, waist-to-hip ratio, android-to-gynoid ratio, and body lean and fat mass. In total, 25 studies were included in the systematic review. The meta-analysis revealed that CO consumption reduces BW [weighted mean difference (WMD) = -0.30 kg; 95% CI: -0.52, -0.08 kg, P = 0.007; n = 23 effect sizes], particularly in participants with type 2 diabetes (WMD = -0.63 kg; 95% CI: -1.09, -0.17 kg, P = 0.007), in studies with a parallel design (WMD = -0.49 kg; 95% CI: -0.85, -0.14 kg, P = 0.006), in nonfeeding trials (WMD = -0.32 kg; 95% CI: -0.55, -0.09 kg, P = 0.006), and when compared with saturated fat (WMD = -0.40 kg; 95% CI: -0.74, -0.06 kg, P = 0.019). CO consumption did not significantly affect any other anthropometric measures or body fat markers (P > 0.05). Although CO consumption results in a modest decrease in BW, no significant effect was observed on other adiposity indexes. Further well-constructed clinical trials that target BW and body composition as their primary outcomes are needed.

Metabolic responses to high-fat diets rich in MUFAv. PUFA

Dietary fatty acid (FA) composition may influence metabolism, possibly affecting weight management. The purpose of this study was to compare the effects of a 5-d diet rich in PUFAv. MUFA. A total of fifteen normal-weight men participated in a randomised cross-over design with two feeding trials (3 d lead-in diet, pre-diet visit, 5-d PUFA- or MUFA-rich diet, post-diet visit). The 5-d diets (50 % fat) were rich in either PUFA (25 % of energy) or MUFA (25 % of energy). At pre- and post-diet visits, subjects consumed breakfast and lunch test meals, rich in the FA for that 5-d diet. Indirect calorimetry was used for 4 h after each meal. There were no treatment differences in fasting metabolism acutely or after the 5-d diet. For acute meal responses before diet, RER was higher for PUFAv. MUFA (0·86 (sem0·01)v. 0·84 (sem0·01),P<0·05), whereas diet-induced thermogenesis (DIT) was lower for PUFAv. MUFA (18·91 (SEM1·46)v. 21·46 (SEM1·34) kJ,P<0·05). After the 5-d diets, the change in RER was different for PUFAv. MUFA (−0·02 (sem0·01)v. 0·00 (sem0·01),P<0·05). Similarly, the change in fat oxidation was greater for PUFAv. MUFA (0·18 (sem0·07)v. 0·04 (sem0·06) g,P<0·05). In conclusion, acutely, a MUFA-rich meal results in lower RER and greater DIT. However, after a 5-d high-fat diet, the change in metabolic responses was greater in the PUFA diet, showing the metabolic adaptability of a PUFA-rich diet.

Oleoylethanolamide: The role of a bioactive lipid amide in modulating eating behaviour

Fatty acid ethanolamides are lipid mediators that regulate a plethora of physiological functions. One such bioactive lipid mediator, oleoylethanolamide (OEA), is a potent agonist of the peroxisome proliferator-activated receptor-alpha (PPAR-α), which modulates increased expression of the fatty acid translocase CD36 that enables the regulation of feeding behaviour. Consumption of dietary fat rich in oleic acid activates taste receptors in the gut activating specific enzymes that lead to the formation of OEA. OEA further combines with PPAR-α to enable fat oxidation in the liver, resulting in enhanced energy production. Evidence suggests that sustained ingestion of a high-fat diet abolishes the anorexic signal of OEA. Additionally, malfunction of the enterocyte that transforms oleic acid produced during fat digestion into OEA might be responsible for reduced satiety and hyperphagia, resulting in overweight and obesity. Thus, OEA anorectic signalling may be an essential element of the physiology and metabolic system regulating dietary fat intake and obesity. The evidence reviewed in this article indicates that intake of oleic acid, and thereby the resulting OEA imparting anorexic properties, is dependent on CD36, PPAR-α, enterocyte fat sensory receptors, histamine, oxytocin and dopamine; leading to increased fat oxidation and enhanced energy expenditure to induce satiety and increase feeding latency; and that a disruption in any of these systems will cease/curb fat-induced satiety.

Benefits of Nut Consumption on Insulin Resistance and Cardiovascular Risk Factors: Multiple Potential Mechanisms of Actions

Epidemiological and clinical studies have indicated that nut consumption could be a healthy dietary strategy to prevent and treat type 2 diabetes (T2DM) and related cardiovascular disease (CVD). The objective of this review is to examine the potential mechanisms of action of nuts addressing effects on glycemic control, weight management, energy balance, appetite, gut microbiota modification, lipid metabolism, oxidative stress, inflammation, endothelial function and blood pressure with a focus on data from both animal and human studies. The favourable effects of nuts could be explained by the unique nutrient composition and bioactive compounds in nuts. Unsaturated fatty acids (monounsaturated fatty acids and polyunsaturated fatty acids) present in nuts may play a role in glucose control and appetite suppression. Fiber and polyphenols in nuts may also have an anti-diabetic effect by altering gut microbiota. Nuts lower serum cholesterol by reduced cholesterol absorption, inhibition of HMG-CoA reductase and increased bile acid production by stimulation of 7-α hydroxylase. Arginine and magnesium improve inflammation, oxidative stress, endothelial function and blood pressure. In conclusion, nuts contain compounds that favourably influence glucose homeostasis, weight control and vascular health. Further investigations are required to identify the most important mechanisms by which nuts decrease the risk of T2DM and CVD.

High Fat Diet with a High Monounsaturated Fatty Acid and Polyunsaturated/Saturated Fatty Acid Ratio Suppresses Body Fat Accumulation and Weight Gain in Obese Hamsters

The aim of this study was to investigate the effect of a high fat diet with experimental oil consisting of 60% MUFAs (monounsaturated fatty acids) with a P/S ratio of 5 on fat deposition and lipid metabolism in obese hamsters. Hamsters were randomly assigned to a control group and a diet-induced obesity group for nine weeks. Then an additional eight-week experimental period began, during which obese hamsters were randomly divided into three groups and fed different amounts of the experimental oil mixture in their diets as follows: 5%, 15%, and 20% w/w (OB-M5, OB-M15, and OB-M20 groups, respectively). The results showed that the OB-M15 and OB-M20 groups had significantly lower blood cholesterol and higher insulin levels. Compared to the control group, the three obese groups exhibited higher hepatic fatty acid synthase activity; however, the acyl-CoA oxidase activities were also enhanced. Although dietary fat content differed, there were no differences in energy intake, final body weights, and epididymal fat weights among the four groups. These results suggest that regardless of whether the specimens had a high fat intake or not, dietary fat containing high MUFAs with a high P/S ratio had beneficial effects on maintaining blood lipid profiles and may not result in body fat accumulation in obese hamsters, possibly by promoting lipolytic enzyme activities.

Central obesity and the Mediterranean diet: A systematic review of intervention trials

Central obesity is associated with chronic low-grade inflammation, and is a risk factor for cardiometabolic syndrome. The Mediterranean diet pattern has a convincing evidence-base for improving cardiometabolic health. This review investigated the impact of Mediterranean diet interventions on central obesity, specifically. A systematic literature search was conducted in the MEDLINE, CINAHL, EMBASE and Cochrane library databases. Search terms included: 'Mediterranean Diet', 'Mediterranean dietary pattern', 'central obesity' and 'visceral fat'. The search was limited to English language and humans ≥18 years. Eighteen articles met the eligibility criteria and reported at least one outcome measure of central obesity with Mediterranean diet intervention. Central obesity measures included waist circumference (16 studies), waist-hip ratio (5 studies) and visceral fat (2 studies). Thirteen (72%) of the studies, totaling 7186 subjects (5168 subjects assigned to a Mediterranean Diet), reported a significant reduction in central obesity with a Mediterranean-type diet. However, seven out of these 13 interventions employed energy restriction, and only three showed a statistically significant favorable effect of the Mediterranean diet relative to a control group. This systematic review highlights the potential for a Mediterranean diet intervention to reduce central obesity and in turn reduce obesity-related chronic disease risk and associated public health burden.

Consumption of alpha-linolenic acid-enriched diacylglycerol induces increase in dietary fat oxidation compared with alpha-linolenic acid-enriched triacylglycerol: A randomized, double-blind trial

Fat metabolism is an important consideration in obesity. Alpha-linolenic acid-enriched diacylglycerol (ALA-DAG), which mainly occurs as ALA esterifies to 1,3-diacyl-sn-glycerol (1,3-DAG), has beneficial effects on fat metabolism and body weight compared with triacylglycerol (TAG). Moreover, compared with ALA-TAG, ALA-DAG enhances β-oxidation activity in the small intestine and liver in rodents. We hypothesized that ALA-DAG consumption may increase dietary fat oxidation compared with ALA-TAG in humans. To examine this hypothesis, we conducted a randomized double-blind cross-over trial in 17 normal and moderately obese men and women (BMI: 25.7±2.0 kg/m², mean±SD). Each participant was assigned to a 4-week intervention period with 2.5 g/day of ALA-DAG or ALA-TAG consumption, followed by a 4-week washout period between consumption of each diet. Dietary fat oxidation, assessed based on the ¹³CO₂ recovery rate in the breath, was significantly increased by ALA-DAG consumption compared with ALA-TAG consumption (17.0±4.5% and 14.1±5.9%, respectively, P<.05). In addition, ALA-DAG consumption significantly decreased the visceral fat area compared with ALA-TAG (102.9±51.9 cm² and 110.9±51.7 cm², respectively; P<.05). These results indicate that ALA-DAG consumption may be useful for preventing obesity.

Indirect Calorimetry: From Bench to Bedside

Accurate determination of energy expenditure (EE) is vitally important yet often neglected in clinical practice. Indirect calorimetry (IC) provides one of the most sensitive, accurate, and noninvasive measurements of EE in an individual. Over the last couple of decades, this technique has been applied to clinical circumstances such as acute illness and parenteral nutrition. Beyond assessing the nutritional needs, it has also shed light on various aspects of nutrient assimilation, thermogenesis, the energetics of physical exercise, and the pathogenesis of obesity and diabetes. However, because of little or no experience with IC provided during medical education, the benefits of IC are poorly appreciated. Newer technology, cost-effectiveness, and a better understanding of how to interpret measurements should lead to more frequent use of IC. This review focuses on the physicochemical background of IC, the various indications for use, techniques and instruments, potential pitfalls in measurement, and the recent advances in technology that has adapted the technique to long-term studies in humans.

Dietary fat composition, total body fat and regional body fat distribution in two Caucasian populations of middle-aged and older adult women

OBJECTIVE

We aimed to study whether dietary fat composition (n-3 and n-6 polyunsaturated fatty acids ratio (PUFAs) and PUFAs and saturated fatty acids (SFAs) ratio) is associated with total body fat (TF) and body fat distribution and whether this association was modified by the presence of chronic disease in middle-aged and elderly women in two population-based cohorts in the Netherlands and Australia.

METHODS

The study was performed in the Rotterdam Study (RS), a prospective cohort study among subjects aged 55 years and older (N = 1182 women) and the Calcium Intake Fracture Outcome Study (CAIFOS), a 5-year randomized controlled trial among women age 70+ (N = 891). At baseline, diet (i.e. PUFAs and SFAs) was measured by validated food frequency questionnaires. TF was assessed using Dual-energy X-ray absorptiometry in both studies and android abdominal fat (AF), gynoid fat (GF) and the android/gynoid ratio (A/G ratio) in the RS but not the CAIFOS. Chronic disease was defined as the presence of cardiovascular disease, diabetes mellitus and cancer.

RESULTS

No association was found between dietary n-3/n-6 PUFAs ratio or SFA/PUFAs ratio with TF in both cohorts. In the RS, a high n-3/n-6 PUFAs ratio was associated with a higher AF (3rd vs. 2nd tertile (reference): β: 0.15; 95% CI: 0.05, 0.24) but not with the A/G ratio. A low SFA/PUFA ratio was associated with a lower AF (1st vs. 2nd tertile (reference): β: -0.12; 95% CI: -0.22, -0.06) but not with the A/G ratio. Presence of chronic disease was found to be a significant effect modifier in both cohorts with regard to n-3/n-6 PUFAs and TF (P < 0.05). In participants without chronic disease, a higher n-3/n-6 PUFAs ratio was associated with a higher TF in the RS cohort (3rd vs. 2nd tertile (reference): β: 0.94; 95% CI: 0.12, 1.76), but this was not replicated in CAIFOS.

CONCLUSION

These findings do not support the hypothesis that dietary fat composition is consistently associated with TF and body fat distribution in women. Future studies should clarify to what extent these findings may be influenced by the presence of chronic disease.

Effects of different amounts and types of dietary fatty acids on the body weight, fat accumulation, and lipid metabolism in hamsters

OBJECTIVES

The aim of this study was to explore the effects of different amounts of dietary fatty acids on body weight, fat accumulation, and lipid metabolism of hamsters.

METHODS

Sixty male golden Syrian hamsters were randomly divided into six groups. Three of the groups (the S groups) were fed experimental diets containing 5%, 15%, and 20% (w/w) fat of soybean oil (S5, S15, and S20, respectively), and the other three groups (the M groups) were fed the same proportions of an experimental oil mixture (M5, M15, and M20, respectively). The experimental oil mixture consisted of 60% monounsaturated fatty acids (MUFAs) and a polyunsaturated-to-saturated fatty acid ratio of 5 with a mixture of soybean and canola oils. Food consumption was measured daily, and body weights were measured weekly. Serum insulin and leptin concentrations were measured and hepatic fatty acid metabolic enzymes and adipose differentiation markers were determined using an enzyme activity analysis and quantitative polymerase chain reaction.

RESULTS

Results showed that the weight and weight gain of the S20 group were significantly greater than those of the other five groups. When the total fat consumption increased, the body weight, weight gain, and adipose tissue weight of the S groups significantly increased, but there were no significant differences in these parameters among the M groups. Serum low-density lipoprotein cholesterol concentrations were significantly lower in the M15 and S15 groups. The S20 group had significantly higher leptin and insulin concentrations and lipoprotein lipase was promoted, but the acetyl-coenzyme A oxidase and carnitine palmitoyltransferase-1, were significantly lower.

CONCLUSIONS

The study demonstrated that a special experimental oil mixture (with 60% MUFAs and a ratio of 5) with high fat can prevent body weight gain and body fat accumulation by lowering insulin concentrations and increasing hepatic lipolytic enzyme activities.

Nutritional Considerations for Performance in Young Athletes

Nutrition is an integral component to any athletes training and performance program. In adults the balance between energy intake and energy demands is crucial in training, recovery, and performance. In young athletes the demands for training and performance remain but should be a secondary focus behind the demands associated with maintaining the proper growth and maturation. Research interventions imposing significant physiological loads and diet manipulation are limited in youth due to the ethical considerations related to potential negative impacts on the growth and maturation processes associated with younger individuals. This necessary limitation results in practitioners providing nutritional guidance to young athletes to rely on exercise nutrition recommendations intended for adults. While many of the recommendations can appropriately be repurposed for the younger athlete attention needs to be taken towards the differences in metabolic needs and physiological differences.

Effect of dietary fatty acid composition on substrate utilization and body weight maintenance in humans

BACKGROUND/PURPOSE

Dietary fat content is a primary factor associated with the increase in global obesity rates. There is a delay in achieving fat balance following exposure to a high-fat (HF) diet (≥ 40% of total energy from fat) and fat balance is closely linked to energy balance. Exercise has been shown to improve this rate of adaptation to a HF diet. Recently, however, the role of dietary fatty acid composition on energy and macronutrient balance has come into question.

METHODS

We chose studies that compared monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA). We have reviewed studies that measured diet-induced thermogenesis (DIT), energy expenditure (EE), or fat oxidation (FOx) in response to a HF meal challenge, or long-term dietary intervention comparing these fatty acids.

RESULTS

While single-meal studies show that SFA induce lower DIT and FOx compared to unsaturated fats, the effect of the degree of unsaturation (MUFA vs. PUFA) appears to yet be determined. Long-term dietary interventions also support the notion that unsaturated fats induce greater EE, DIT, and/or FOx versus SFA and that a high MUFA diet induces more weight loss compared to a high SFA diet. Sex and BMI status also affect the metabolic responses to different fatty acids; however, more research in these areas is warranted.

CONCLUSION

SFA are likely more obesigenic than MUFA, and PUFA. The unsaturated fats appear to be more metabolically beneficial, specifically MUFA ≥ PUFA > SFA, as evidenced by the higher DIT and FOx following HF meals or diets.

Health benefits of nut consumption with special reference to body weight control

Nuts are an integral part of the Mediterranean food patterns, and their incorporation into the regular diets of human beings is believed to provide many health benefits. The recent recognition of nuts as "heart-healthy" foods by the U.S. Food and Drug Administration has given a major boost to the positive image of nuts. Nut consumption has been associated with several health benefits, such as antioxidant, hypocholesterolemic, cardioprotective, anticancer, anti-inflammatory, and antidiabetic benefits, among other functional properties. However, although nuts possess these many health benefits, their consumption has been hampered by a lack of adequate information regarding those benefits. In addition, because nuts are energy-dense foods with high-fat content, there is a misconception among consumers that increased consumption may lead to unwanted gain in body weight with the risk of developing overweight/obesity. Nonetheless, available epidemiologic studies and short-term controlled feeding trials have supported the theory that the inclusion of nuts in the typical diet does not induce weight gain, despite an expected increase in total caloric intake. To address the misperception about nuts and body weight gain, the present review focuses mainly on the relation between nut consumption and body weight gain, in the context of the many health benefits of nuts.

Decreased plasma cholesterol concentrations after PUFA-rich diets are not due to reduced cholesterol absorption/synthesis

Plasma cholesterol concentrations increase with consumption of high saturated fatty acid (SFA) and decrease with high polyunsaturated fatty acid (PUFA) diets, leading to shifts in lipid levels consistent with reduction in heart disease risk. Direct measurements of cholesterol absorption, one of the key regulators of plasma cholesterol levels, have not been performed in humans after consumption of high PUFA diets. Thus, cholesterol absorption and fractional synthesis rates (FSRs) were measured in 16 healthy adults (8 males and 9 females) using a randomized cross-over study with a diet containing high (PUFA/SFA) P/S ratio (2:1) and a low P/S ratio (0.5:1). Cholesterol absorption and fractional cholesterol synthetic rates were measured using stable isotopes after 20 days of dietary intervention. Diet did not affect cholesterol absorption or synthesis. There was a significant decrease in plasma cholesterol concentrations (P < 0.02), specifically LDL-cholesterol (P < 0.02), without a change in HDL-cholesterol or triacylglycerol concentrations. Intraluminal cholesterol solubilization and plasma sterol (cholesterol biosynthetic intermediates and plant sterols) levels were not affected by diet. Thus, consumption of diets with a high P/S ratio reduces plasma total and LDL-cholesterol concentrations independent of shifts in cholesterol absorption or synthesis.

Effects of Different Dietary Fat Types on Postprandial Appetite and Energy Expenditure

OBJECTIVE

Observational studies suggest that monounsaturated (MUFA) and trans fatty acids (TRANS) are more fattening than polyunsaturated fatty acids (PUFA). Therefore, the aim of this study was to investigate the acute effect of intake of PUFA, MUFA, or TRANS on appetite and energy expenditure (EE).

RESEARCH METHODS AND PROCEDURES

Three test meals were randomly given in a cross-over design to 19 overweight (BMI: 26.8 +/- 0.4 kg/m2), young (25.2 +/- 0.7 years) men. The fat-rich breakfasts (0.8 g fat/kg body weight, 60% energy from fat) varied only in the source of C:18-fat. EE was measured continuously in a respiration chamber, and appetite sensations were rated by visual analog scales before and every 30 minutes, for 5 hours, after the meal. After 5 hours, an ad libitum meal was served, and energy intake was registered. Sensory evaluations of all meals were given using visual analog scales. Data were analyzed by two-way ANOVA.

RESULTS

There were no differences in basal or postprandial values of appetite ratings and EE, in subsequent ad libitum energy intake, or in the sensory evaluation of the test meals among the 3 test days.

DISCUSSION

Giving acutely large amounts of MUFA, PUFA, or TRANS did not impose any differences in appetite and EE in overweight humans. However, studies with extended protocols and other subject groups are warranted to investigate the long-term effect of dietary fat quality on the regulation of energy balance and body weight.

Evaluation of the salivary proteome as a surrogate tissue for systems biology approaches to understanding appetite

Current measurement of appetite depends upon tools that are either subjective (visual analogue scales), or invasive (blood). Saliva is increasingly recognised as a valuable resource for biomarker analysis. Proteomics workflows may provide alternative means for the assessment of appetitive response. The study aimed to assess the potential value of the salivary proteome to detect novel biomarkers of appetite using an iTRAQ-based workflow. Diurnal variation of salivary protein concentrations was assessed. A randomised, controlled, crossover study examined the effects on the salivary proteome of isocaloric doses of various long chain fatty acid (LCFA) oil emulsions compared to no treatment (NT). Fasted males provided saliva samples before and following NT or dosing with LCFA emulsions. The oil component of the DHA emulsion contained predominantly docosahexaenoic acid and the oil component of OA contained predominantly oleic acid. Several proteins were present in significantly (p<0.05) different quantities in saliva samples taken following treatments compared to fasting samples. DHA caused alterations in thioredoxin and serpin B4 relative to OA and NT. A further study evaluated energy intake (EI) in response to LCFA in conjunction with subjective appetite scoring. DHA was associated with significantly lower EI relative to NT and OA (p=0.039). The collective data suggest investigation of salivary proteome may be of value in appetitive response. This article is part of a Special Issue entitled: Proteomics: The clinical link.

Nuts improve diet quality compared to other energy-dense snacks while maintaining body weight

Previous studies have reported that regular nut consumption reduces cardiovascular disease (CVD) risk and does not promote weight gain despite the fact that nuts are energy-dense. However, no studies have investigated the body composition of those regularly consuming nuts compared to similar intakes of other snacks of equal energy density. This parallel study (n = 118) examined the effects of providing daily portions (~1100 kJ/d) of hazelnuts, chocolate, or potato crisps compared to a control group receiving no snacks for twelve weeks. Effects on body weight and composition, blood lipids and lipoproteins, resting metabolic rate (RMR), appetite indices, and dietary quality were compared. At week 12, there was no significant difference in any of the outcome measurements between the groups except for dietary quality, which improved significantly in the nut group. Nuts can be incorporated into the diet without adversely affecting body weight and can improve diet quality.

Increased intake of dietary polyunsaturated fat does not promote whole body or preferential abdominal fat mass loss in overweight adults

OBJECTIVE

There is evidence that increasing the proportion of polyunsaturated fatty acids (PUFA) in a diet can enhance the rate of fat oxidation acutely. Higher PUFA in a diet has also been associated with greater abdominal fat loss in longer term studies. This study aimed to investigate if higher PUFA intake would result in greater fat mass loss over a 12-week period, mainly from the abdominal region.

METHODS

Data at the 12-week time point from two weight loss studies, both comparing high PUFA versus low PUFA diets was, accessed for 141 overweight subjects from the same area. Specifically, data on anthropometric measurements (weight, height, BMI, body composition, waist and hip circumference, SAT, VAT) and dietary intake were analyzed. The relationship between fat mass and VAT changes was examined using a differential equation.

RESULTS

Energy consumption decreased significantly in both study groups. The low fat groups decreased total dietary fat while the HPUFA groups increased PUFA intake significantly. All anthropometric measurements reduced significantly over time but there was no difference between the two dietary groups. The relationship between fat mass and visceral adipose tissue (VAT) loss was allometric.

CONCLUSION

A higher PUFA intake did not lead to greater fat mass loss and there was no additional preferential loss of VAT following higher PUFA consumption.

Influence of dietary fatty acid composition and exercise on changes in fat oxidation from a high-fat diet

Acute high-fat (HF) diets can lead to short-term positive fat balances until the body increases fat oxidation to match intake. The purpose of this study was to examine the effects of a HF diet, rich in either mono-unsaturated or saturated fatty acids (FAs) and exercise, on the rate at which the body adapts to a HF diet.13C-labeled oleate and 2H-labeled palmitate were also given to determine the contribution of exogenous vs. global fat oxidation. Eight healthy men (age of 18–45 yr; body mass index of 22 ± 3 kg/m2) were randomized in a 2 × 2 crossover design. The four treatments were a high saturated fat diet with exercise (SE) or sedentary (SS) conditions and a high monounsaturated fat diet with exercise (UE) or sedentary (US) conditions. Subjects stayed for 5 days in a metabolic chamber. All meals were provided. On day 1, 30% of energy intake was from fat, whereas days 2–5 had 50% of energy as fat. Subjects exercised on a stationary cycle at 45% of maximal oxygen uptake for 2 h each day. Respiratory gases and urinary nitrogen were collected to calculate fat oxidation. Change from day 1 to day 5 showed both exercise treatments increased fat oxidation (SE: 76 ± 30 g, P = 0.001; UE: 118 ± 31 g, P < 0.001), whereas neither sedentary condition changed fat oxidation (SS: −10 ± 33 g, P = not significant; US: 41 ± 14 g, P = 0.07). No differences for dietary FA composition were found. Exercise led to a faster adaptation to a HF diet by increasing fat oxidation and achieving fat balance by day 5. Dietary FA composition did not differentially affect 24-h fat oxidation.

No evidence of differential effects of SFA, MUFA or PUFA on post-ingestive satiety and energy intake: a randomised trial of fatty acid saturation

BACKGROUND

High fat diets have long been associated with weight gain and obesity, and the weak satiety response elicited in response to dietary lipids is likely to play a role. Suppression of appetite and food intake has consistently been shown to be diminished with high fat relative to either high protein or carbohydrate meals. There is however some evidence that the satiating capacity of lipids may be modulated when physicochemical properties are altered, but studies investigating the effect of lipid saturation on appetite have generated inconsistent findings. This study investigated the effects of changes in fatty acid saturation on post-ingestive satiety and energy intake.

METHODS

High-fat (HF) test breakfasts (2.0 MJ) containing 26 g lipid were given to 18 healthy, lean men in a 3 treatment randomised cross-over design, each treatment separated by a washout of at least 3 days. The breakfasts were high in saturated (SFA, 65% of total fat), polyunsaturated (PUFA, 76%) or monounsaturated (MUFA, 76%) fatty acids, and comprised 2 savoury muffins. Participants rated appetite sensations using visual analogue scales (VAS) to assess palatability immediately following the meals, and hunger and fullness prior to the HF breakfast and throughout the day. Energy intake was measured by covert weighing of a lunch meal which was served 3.5 h after the breakfast, and from which the participants ate ad libitum.

RESULTS

There was no difference in VAS ratings of pleasantness, visual appearance, smell, taste, aftertaste and overall palatability between the 3 high-fat test breakfasts. However, there was also no differential effect of the 3 treatments on ratings of hunger, fullness, satisfaction or prospective food consumption during the 3.5 h following the breakfast meal and over the full 6 h experiment. Energy and macronutrient intake at lunch also did not differ between treatments (mean, sem; SFA: 5275.9 +/- 286.5 kJ; PUFA: 5227.7 +/- 403.9 kJ; MUFA: 5215.6 +/- 329.5 kJ; P > 0.05). The maximum difference in energy intake between treatments was less than 2%.

CONCLUSIONS

There was no evidence of a difference in post-ingestion satiety between high fat meals which differed in saturation profile in this group of lean, healthy men.

Effects of different ratios of monounsaturated and polyunsaturated fatty acids to saturated fatty acids on regulating body fat deposition in hamsters

OBJECTIVE

Effects of monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid consumption on regulating body fat accumulation and body weight gain are controversial between animal and human studies.

METHODS

We designed a 2 x 2 factorial study, with two levels of MUFAs (60% and 30%) and two levels of polyunsaturated-to-saturated fatty acid (P/S) ratio (5 and 3) to prepare four kinds of experimental oils consisting of 60% MUFAs with a high or low P/S ratio (HMHR or HMLR, respectively) or 30% MUFAs with a high or low P/S ratio (LMHR or LMLR, respectively). Thirty-two male golden Syrian hamsters were randomly divided into four groups and fed the experimental diets containing 15% (w/w) fat for 12 wk.

RESULTS

No difference was observed in the mean daily food intake. Hamsters fed the LMLR diet had increased weight gain, epididymal and retroperitoneal white adipose tissues, plasma non-esterified fatty acids, insulin, hepatic acetyl coenzyme A carboxylase and malic enzyme activities, and mRNA expressions of peroxisome proliferator-activated receptor-alpha and sterol regulatory element-binding protein-1c among all groups (P < 0.05). Hamsters fed the HMHR diet had lower plasma insulin levels and hepatic acetyl coenzyme A carboxylase activities among groups (P < 0.05) and elevated hepatic acyl coenzyme A oxidase and carnitine palmitoyltransferase-I activities compared with those fed the LMLR diet (P < 0.05).

CONCLUSION

Hamsters fed the LMLR diet had increased weight gain and body fat accumulation, whereas the HMHR diet appeared to be beneficial in preventing white adipose tissue accumulation by decreasing plasma insulin levels and increasing hepatic lipolytic enzyme activities involved in beta-oxidation.

Could the quality of dietary fat, and not just its quantity, be related to risk of obesity?

This review focuses on the possible association between types of fatty acids and weight change. It examines the biological plausibility underlining these associations and the evidence obtained to date from clinical trials and epidemiological studies. Animal studies have shown that dietary short- and medium-chain fatty acids compared to long-chain fatty acids appear to promote weight loss. Similarly, monounsaturated fatty acids (MUFAs) appear to favor weight loss compared to saturated fatty acids (SFAs) in human studies. The structure of fatty acids seems to affect their degree of oxidation and deposition. Although results are conflicting, human studies follow the general trend reported in animal studies. These trials suggest that some fatty acids are prone to oxidation and some others lead to fat storage when comparing isocaloric diets. For instance, n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic and docosahexaenoic acids are preferentially oxidizied to other PUFA but results remain inconsistent. Epidemiological studies concerning this issue reported that total dietary fat, which includes MUFA, PUFA, and SFA could increase the risk of obesity, but results are few and conflicting. The rising biological plausibility linking dietary fat quality and risk of obesity, together with the rather recent addition of fatty acids content in food composition tables, support the need for major epidemiological studies in that area.

Nuts: source of energy and macronutrients

On the basis of the high fat content of nuts, they are traditionally considered as foods that provide a high amount of energy. However, epidemiologic and clinical observations do not indicate an association between nut intake and increased BMI. There is a notorious variability in macronutrient composition among nuts, although they have some consistent patterns. Nuts contain all major macronutrients: protein, carbohydrate, and fat. The total protein content is relatively high, which makes them a good source of plant protein (especially for vegetarians). Although nuts contain low amounts of some essential amino acids, this is not a nutritional concern due to the complement of protein. In addition, nuts have a low lysine:arginine ratio, which is inversely associated with the risk of developing hypercholesterolemia and atherosclerosis. Carbohydrates are the second highest macronutrient in nuts in terms of total calories provided. The fat fraction is characterized by a high amount of unsaturated fatty acids and a low content of saturated fatty acids. In conclusion, the high content in unsaturated fatty acids, the low lysine:arginine ratio, and the presence of other bioactive molecules (such as fibre, phytosterols, vitamin and other antioxidants, and minerals) make the addition of nuts to healthy diets a useful tool for the prevention of cardiovascular heart diseases.

A comparison of the influence of a high-fat diet enriched in monounsaturated fatty acids and conventional diet on weight loss and metabolic parameters in obese non-diabetic and Type 2 diabetic patients

AIMS

The aim of our study was to compare the influence of a hypocaloric, high-fat diet enriched with MUFA (M) and conventional diet (C) on weight loss and metabolic parameters in obese non-diabetic and obese Type 2 diabetic subjects over a 3-month period. It was our hypothesis that the enriched diet would be more effective in decreasing blood glucose and glycated haemoglobin (HbA(1c)) than the control diet.

METHODS

Twenty-seven Type 2 diabetic patients (54.5 +/- 3.5 years; DM), treated with diet or oral glucose-lowering agents, and 31 obese non-diabetic subjects (53.6 +/- 3.5 years; OB) were randomized to M or C. Individual calculations of energy requirements were based on the formula: [resting energy expenditure (REE) x 1.5] - 600 kcal. Subjects were assessed by a dietitian every 2 weeks and by a physician every month. Statistical analyses were carried out between the four groups--DM/M, DM/C, OB/M and OB/C--using pair Student's test and anova.

RESULTS

After 3 months, body weight, waist-hip ratio, total body fat, levels of C-peptide, triglycerides and homeostasis model assessment (HOMA) decreased in all four groups (P < 0.01). However, fasting blood glucose and HbA(1c) decreased (P < 0.01) and high-density lipoprotein cholesterol increased significantly only in the DM/M group (P < 0.05). In general, M was well tolerated.

CONCLUSIONS

Individualized M and C diets were successful in improving metabolic and anthropometric parameters in both the obese non-diabetic and the Type 2 diabetic subjects. Although the superiority of the higher fat diet did not reach statistical significance, the decline in blood glucose and HbA(1c) in the Type 2 diabetic group on M was encouraging.

THE COW AS A MODEL TO STUDY FOOD INTAKE REGULATION

Animal models have been invaluable for studying aspects of food intake regulation that for various reasons cannot be observed in humans. The dairy cow is a unique animal model because of an unrivaled energy requirement; its great drive to eat results in feeding behavior responses to treatments within the physiological range. Cows' docile nature and large size make them ideal for measuring temporal treatment effects because digestion and absorption kinetics and responses in endocrine systems, gene expression, metabolite pools and fluxes, and feeding behavior can be measured simultaneously. Thus, cows are important models to investigate interactions of short-term signals regulating food intake. Furthermore, different physiological states throughout the lactation cycle provide powerful models to study how short- and long-term signals interact to affect long-term energy status. The use of the cow as a model can lead to breakthroughs in understanding the complex interactions of signals regulating food intake.

Substrate metabolism, nutrient balance and obesity development in children and adolescents: a target for intervention?

Obesity results from the organism's inability to maintain energy balance over a long term. Childhood obesity and its related factors and pathological consequences tend to persist into adulthood. A cluster of factors, including high energy density in the diet (high fat intake), low energy expenditure, and disturbed substrate oxidation, favour the increase in fat mass. Oxidation of three major macronutrients and their roles in the regulation of energy balance, particularly in children and adolescents, are discussed. Total glucose oxidation is not different between obese and lean children; exogenous glucose utilization is higher whereas endogenous glucose utilization is lower in obese compared with lean children. Carbohydrate composition of the diet determines carbohydrate oxidation regardless of fat content of the diet. Both exogenous and endogenous fat oxidation are higher in obese than in lean subjects. The influence of high fat intake on accumulation of fat mass is operative rather over a long term. Several future directions are addressed, such that a combination of increased physical activity and modification in diet composition, in terms of energy density and glycemic index, is recommended for children and adolescents.

Insulin sensitivity is increased and fat oxidation after a high-fat meal is reduced in normal-weight healthy men with strong familial predisposition to overweight

OBJECTIVE

To evaluate whether postprandial abnormalities of energy expenditure and/or lipid oxidation are present in healthy, normal-weight subjects with a strong family history of obesity and thus at high risk to become obese.

DESIGN

Case-control study.

SUBJECTS

A total of 16 young healthy men participated in the study. Eight subjects had both parents overweight (father's and mother's body mass index (BMI) >25 kg/m(2)) and eight had both parents with normal body weight (father's and mother's BMI<25 kg/m(2), respectively). The group of subjects with overweight parents was similar to that with normal-weight parents (control group) in terms of BMI (23.7+/-1.7 vs 22.7+/-1.1 kg/m(2)) (M+/-s.d.) and fat-free body mass (FFM) (60.5+/-4.9 vs 58.4+/-2.0 kg), but was slightly older than the control group (25.4+/-3.3 vs 22.7+/-2.4 y; P<0.05).

MEASUREMENTS

Energy expenditure (EE) was measured by indirect calorimetry, and blood samples were taken for the evaluation of metabolic variables in the fasting state and every hour for 8 h after a standard fat-rich meal (protein 15%, carbohydrate 34%, fat 51%, 4090 kJ).

RESULTS

: Fasting plasma glucose, cholesterol, HDL-cholesterol, triglyceride, free fatty acid (FFA) and leptin concentrations were similar in both groups of participants, but subjects with overweight parents has significantly lower plasma insulin concentrations (5.11+/-0.51 vs 7.07+/-1.56 microU/ml; P<0.007) and HOMA index of insulin resistance (1.1+/-0.1 vs 1.6+/-0.4; P<0.01). Postprandial plasma glucose, triglyceride, FFA and leptin concentrations were similar in the two groups, whereas insulin levels were significantly lower in the group with both parents overweight at 3, 5, 6, 7 and 8 h. Fasting and postprandial EE, and fasting lipid and carbohydrate oxidation were similar in both groups. On the contrary, postprandial carbohydrate oxidation (incremental area under curve) was significantly higher (196.25+/-94.75 vs 75.88+/-74.72 mg/kg FFM x 8 h; P<0.007) and that of lipid oxidation lower (90.93+/-80.32 vs 163.68+/-108.22 mg/kg FFM x 8 h; P<0.05) in the group of subjects with overweight parents.

CONCLUSION

Normal-weight subjects with a strong family history of obesity present a reduced lipid oxidation in the postprandial period and a metabolic profile characterized by low plasma insulin levels and the HOMA index, which is compatible with increased insulin sensitivity. These metabolic characteristics may be considered as early predictors of weight gain and are probably genetically determined.

The acute effects of olive oil v. cream on postprandial thermogenesis and substrate oxidation in postmenopausal women

The influence of the source of dietary fat on postprandial thermogenesis and substrate oxidation rates, was examined in twelve postmenopausal women aged 57-73 years, with BMI 21.9-38.3 kg/m(2). A single blind, randomised, paired comparison of two high-fat, isoenergetic, mixed test meals was conducted. The major source of fat was either cream (CREAM) or extra virgin olive oil (EVOO). RMR, diet-induced thermogenesis (DIT) and substrate oxidation rates over 5 h were measured by indirect calorimetry. There were no differences in body weight, RMR, fasting carbohydrate or fat oxidation rates between the two occasions. DIT (EVOO 97 (SD 46) v. CREAM 76 (SD 69) kJ/5 h and EVOO 5.2 (SD 2.5) v. CREAM 4.1 (SD 3.7)% energy) did not differ between the two test meals. The postprandial increase in carbohydrate oxidation rates, relative to their respective fasting values (DeltaCOX), was significantly lower following the EVOO meal (EVOO 10.6 (SD 8.3) v. CREAM 17.5 (SD 10) g/5 h; paired t test, P=0.023), while postprandial fat oxidation rates (DeltaFOX) were significantly higher (EVOO 0.0 (SD 4.4) v. CREAM -3.6 (sd 4.0) g/5 h; P=0.028). In the eight obese subjects, however, DIT was significantly higher following the EVOO meal (EVOO 5.1 (SD 2.0) v. CREAM 2.5 (sd 2.9) %; P=0.01). This was accompanied by a significantly lower DeltaCOX (EVOO 10.9 (SD 9.9) v. CREAM 17.3 (SD 10.5) g/5 h; P=0.03) and significantly higher DeltaFOX (EVOO 0.11 (SD 4.4) v. CREAM -4.1 (SD 4.5) g/5 h, P=0.034). The present study showed that olive oil significantly promoted postprandial fat oxidation and stimulated DIT in abdominally obese postmenopausal women.

Nut consumption, body weight and insulin resistance

The beneficial effects of nuts on cardiovascular health are well known. However, since nuts provide a high caloric and fat content, some concern exists regarding a potential detrimental effect on body weight and insulin resistance. The current data available did not support such a negative effect of nut consumption on the short term or when nuts are included on diets that meet energy needs. Furthermore, there is some intriguing evidence that nuts can help to regulate body weight and protect against type II diabetes. This, however, still has to be proved and more research is needed to address the specific effects of nuts on satiety, energy balance, body weight and insulin resistance.

Nut consumption and body weight

Frequent nut consumption is associated with lower rates of coronary artery disease (CAD). Also, nut-rich diets improve the serum lipid profile of participants in dietary intervention trials. However, nuts are fatty foods, and in theory their regular consumption may lead to body weight gain. Because obesity is a major public health problem and a risk factor for CAD, clinicians and policy makers ponder several questions. Will hypercholesterolemic patients advised to consume nuts gain weight? Is recommending increased nut consumption to the general population for CAD prevention sound public health advice? Epidemiologic studies indicate an inverse association between frequency of nut consumption and body mass index. In well-controlled nut-feeding trials, no changes in body weight were observed. Some studies on free-living subjects in which no constraints on body weight are imposed show a nonsignificant tendency to lower weight while subjects are on the nut diets. In another line of evidence, preliminary data indicate that subjects on nut-rich diets excrete more fat in stools. Further research is needed to study the effects of nut consumption on energy balance and body weight. In the meantime, the available cumulative data do not indicate that free-living people on self-selected diets including nuts frequently have a higher body mass index or a tendency to gain weight.

Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men

A randomised crossover study of eight overweight or obese men (aged 24-49 years, BMI 25.5-31.3 kg/m(2)), who followed two diets for 4 weeks each, was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition, but differing energy content. The % total energy from saturated fat, monounsaturated fat and polyunsaturated fat was 24, 13 and 3 % respectively on the saturated fatty acid (SFA)-rich diet and 11, 22 and 7 % respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80 % of the unsaturated fats consumed on both diets. Body composition, blood pressure, energy expenditure (resting and postprandial metabolic rates, substrate oxidation rate, physical activity), serum lipids, the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P< or =0.05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2.1 (SE 0.4) kg, P=0.0015) and fat mass (-2.6 (SE 0.6) kg, P=0.0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake, energy expenditure, substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat, predominantly MUFA, can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.

Insulin sensitivity is increased and fat oxidation after a high-fat meal is reduced in normal-weight healthy men with strong familial predisposition to overweight

OBJECTIVE

To evaluate whether postprandial abnormalities of energy expenditure and/or lipid oxidation are present in healthy, normal-weight subjects with a strong family history of obesity and thus at high risk to become obese.

DESIGN

Case-control study.

SUBJECTS

A total of 16 young healthy men participated in the study. Eight subjects had both parents overweight (father's and mother's body mass index (BMI) >25 kg/m(2)) and eight had both parents with normal body weight (father's and mother's BMI<25 kg/m(2), respectively). The group of subjects with overweight parents was similar to that with normal-weight parents (control group) in terms of BMI (23.7+/-1.7 vs 22.7+/-1.1 kg/m(2)) (M+/-s.d.) and fat-free body mass (FFM) (60.5+/-4.9 vs 58.4+/-2.0 kg), but was slightly older than the control group (25.4+/-3.3 vs 22.7+/-2.4 y; P<0.05).

MEASUREMENTS

Energy expenditure (EE) was measured by indirect calorimetry, and blood samples were taken for the evaluation of metabolic variables in the fasting state and every hour for 8 h after a standard fat-rich meal (protein 15%, carbohydrate 34%, fat 51%, 4090 kJ).

RESULTS

Fasting plasma glucose, cholesterol, HDL-cholesterol, triglyceride, free fatty acid (FFA) and leptin concentrations were similar in both groups of participants, but subjects with overweight parents has significantly lower plasma insulin concentrations (5.11+/-0.51 vs 7.07+/-1.56 microU/ml; P<0.007) and HOMA index of insulin resistance (1.1+/-0.1 vs 1.6+/-0.4; P<0.01). Postprandial plasma glucose, triglyceride, FFA and leptin concentrations were similar in the two groups, whereas insulin levels were significantly lower in the group with both parents overweight at 3, 5, 6, 7 and 8 h. Fasting and postprandial EE, and fasting lipid and carbohydrate oxidation were similar in both groups. On the contrary, postprandial carbohydrate oxidation (incremental area under curve) was significantly higher (196.25+/-94.75 vs 75.88+/-74.72 mg/kg FFM x 8 h; P<0.007) and that of lipid oxidation lower (90.93+/-80.32 vs 163.68+/-108.22 mg/kg FFM x 8 h; P<0.05) in the group of subjects with overweight parents.

CONCLUSION

Normal-weight subjects with a strong family history of obesity present a reduced lipid oxidation in the postprandial period and a metabolic profile characterized by low plasma insulin levels and the HOMA index, which is compatible with increased insulin sensitivity. These metabolic characteristics may be considered as early predictors of weight gain and are probably genetically determined.