Thermophysiological adaptations to passive mild heat acclimation.

Passive mild heat acclimation (PMHA) reflects realistic temperature challenges encountered in everyday life. Active heat acclimation, combining heat exposure and exercise, influences several important thermophysiological parameters; for example, it decreases core temperature and enhances heat exchange via the skin. However, it is unclear whether PMHA elicits comparable adaptations. Therefore, this study investigated the effect of PMHA on thermophysiological parameters. Participants were exposed to slightly increased temperatures (∼33°C/22% RH) for 6 h/d over 7 consecutive days. To study physiologic responses before and after PMHA, participants underwent a temperature ramp (UP), where ambient temperature increased from a thermoneutral value (28.8 ± 0.3°C) to 37.5 ± 0.6°C. During UP, core and skin temperature, water loss, cardiovascular parameters, skin blood flow and energy expenditure were measured. Three intervals were selected to compare data before and after PMHA: baseline (minutes 30-55: 28.44 ± 0.21°C), T1 (minutes 105-115: 33.29 ± 0.4°C) and T2 (minutes 130-140: 35.68 ± 0.61°C). After 7 d of PMHA, core (T1: -0.13 ± 0.13°C, P = 0.011; T2: -0.14 ± 0.15°C, P = 0.026) and proximal skin temperature (T1: -0.22 ± 0.29°C, P = 0.029) were lower during UP, whereas distal skin temperature was higher in a thermoneutral state (baseline: +0.74 ± 0.77°C, P = 0.009) and during UP (T1: +0.49 ± 0.76°C, P = .057 (not significant), T2:+0.51 ± 0.63°C, P = .022). Moreover, water loss was reduced (-30.5 ± 33.3 ml, P = 0.012) and both systolic (-7.7 ± 7.7 mmHg, P = 0.015) and diastolic (-4.4 ± 4.8 mmHg, P = 0.001) blood pressures were lowered in a thermoneutral state. During UP, only systolic blood pressure was decreased (T2: -6.1 ± 4.4 mmHg, P = 0.003). Skin blood flow was significantly decreased at T1 (-28.35 ± 38.96%, P = 0.037), yet energy expenditure remained unchanged. In conclusion, despite the mild heat stimulus, we show that PMHA induces distinct thermophysiological adaptations leading to increased resilience to heat.

Diet-induced weight loss decreases adipose tissue oxygen tension with parallel changes in adipose tissue phenotype and insulin sensitivity in overweight humans.

BACKGROUND/OBJECTIVES: Although adipose tissue (AT) hypoxia is present in rodent models of obesity, evidence for this in humans is limited. Here, we investigated the effects of diet-induced weight loss (WL) on abdominal subcutaneous AT oxygen tension (pO2), AT blood flow (ATBF), AT capillary density, AT morphology and transcriptome, systemic inflammatory markers and insulin sensitivity in humans. SUBJECTS/METHODS: Fifteen overweight and obese individuals underwent a dietary intervention (DI), consisting of a 5-week very-low-calorie diet (VLCD, 500 kcal day-1; WL), and a subsequent 4-week weight stable diet (WS). Body composition, AT pO2 (optochemical monitoring), ATBF (133Xe washout), and whole-body insulin sensitivity were determined, and AT biopsies were collected at baseline, end of WL (week 5) and end of WS (week 9). RESULTS: Body weight, body fat percentage and adipocyte size decreased significantly during the DI period. The DI markedly decreased AT pO2 and improved insulin sensitivity, but did not alter ATBF. Finally, the DI increased AT gene expression of pathways related to mitochondrial biogenesis and non-mitochondrial oxygen consumption. CONCLUSIONS: VLCD-induced WL markedly decreases abdominal subcutaneous AT pO2, which is paralleled by a reduction in adipocyte size, increased AT gene expression of mitochondrial biogenesis markers and non-mitochondrial oxygen consumption pathways, and improved whole-body insulin sensitivity in humans.

Weight loss-induced cellular stress in subcutaneous adipose tissue and the risk for weight regain in overweight and obese adults.

BACKGROUND/OBJECTIVE: Weight loss is often followed by weight regain after the dietary intervention (DI). Cellular stress is increased in adipose tissue of obese individuals. However, the relation between cellular stress and weight regain is unclear. Previously, we observed increased adipose tissue cellular stress of participants regaining weight compared with participants maintaining weight loss. In the current study, we further investigated the relation between weight regain and changes in the expression of stress-related genes and stress protein levels to determine possible predictors of weight regain. PARTICIPANTS/METHODS: In this randomized controlled trial, sixty-one healthy overweight/obese participants followed a DI of either a 5-week very-low-calorie diet (500 kcal per day) or a 12-week low-calorie diet (1250 kcal per day; WL period) with a subsequent 4-week weight stable diet (WS period), and a 9-month follow-up. The WL and WS period taken together was named the DI. Abdominal subcutaneous adipose tissue biopsies were collected in 53 participants for microarray and liquid chromatography-mass spectrometry analysis. RNA and protein levels for a broad set of stress-related genes were correlated to the weight regain percentage. RESULTS: Different gene sets correlated to weight regain percentage during WS and DI. Bioinformatics clustering suggests that during the WS phase-defined genes for actin filament dynamics, glucose handling and nutrient sensing are related to weight regain. HIF-1 (hypoxia-inducible factor-1) is indicated as an important regulator. With regard to DI, clustering of correlated genes indicate that LGALS1, ENO1 and ATF2 are important nodes for conferring risk for weight regain. CONCLUSIONS: Our present findings indicate that the risk for weight regain is related to expression changes of distinct sets of stress-related genes during the first 4 weeks after returning to energy balance, and during the DI. Further research is required to investigate the mechanistic significance of these findings and find targets for preventing weight regain.

Adipose tissue gene expression is differentially regulated with different rates of weight loss in overweight and obese humans.

BACKGROUND/OBJECTIVES: Moderate weight loss (WL) can ameliorate adverse health effects associated with obesity, reflected by an improved adipose tissue (AT) gene expression profile. However, the effect of rate of WL on the AT transcriptome is unknown. We investigated the global AT gene expression profile before and after two different rates of WL that resulted in similar total WL, and after a subsequent weight stabilization period. SUBJECTS/METHODS: In this randomized controlled trial, 25 male and 28 female individuals (body mass index (BMI): 28-35 kg m-2) followed either a low-calorie diet (LCD; 1250 kcal day-1) for 12 weeks or a very-low-calorie diet (VLCD; 500 kcal day-1) for 5 weeks (WL period) and a subsequent weight stable (WS) period of 4 weeks. The WL period and WS period together is termed dietary intervention (DI) period. Abdominal subcutaneous AT biopsies were collected for microarray analysis and gene expression changes were calculated for all three periods in the LCD group, VLCD group and between diets (ΔVLCD-ΔLCD). RESULTS: WL was similar between groups during the WL period (LCD: -8.1±0.5 kg, VLCD: -8.9±0.4 kg, difference P=0.25). Overall, more genes were significantly regulated and changes in gene expression appeared more pronounced in the VLCD group compared with the LCD group. Gene sets related to mitochondrial function, adipogenesis and immunity/inflammation were more strongly upregulated on a VLCD compared with a LCD during the DI period (positive ΔVLCD-ΔLCD). Neuronal and olfactory-related gene sets were decreased during the WL period and DI period in the VLCD group. CONCLUSIONS: The rate of WL (LCD vs VLCD), with similar total WL, strongly regulates AT gene expression. Increased mitochondrial function, angiogenesis and adipogenesis on a VLCD compared with a LCD reflect potential beneficial diet-induced changes in AT, whereas differential neuronal and olfactory regulation suggest functions of these genes beyond the current paradigm.

Evaluation of an 18-month commercial multidisciplinary obesity treatment programme.

The treatment of obesity is an often studied subject. Although reductions in weight and improvements in cardiometabolic risk factors are important aims of obesity treatment, improvements in quality of life and eating behaviour are also relevant outcomes. In this practice-based study, we evaluated an 18-month commercial multidisciplinary obesity treatment programme and report on treatment results for weight, cardiometabolic risk factors, eating behaviour and quality of life. From a local commercial obesity treatment centre, 426 subjects (65% female; 45.4 ± 12.2 years; body mass index 40.0 ± 6.6 kg m(-2)) were recruited. Measurements of body weight, height, body composition, waist circumference and blood pressure were scheduled at baseline and every 3 months, whereas fasting blood collections were scheduled at baseline and every 6 months. At the same time points, participants were asked to fill in questionnaires on dietary intake, eating behaviour and quality of life. After 18 months of treatment programme, average weight change [mean (95% confidence interval)] was -10.9 kg (-14.8 to -7.0; P < 0.001) for the completers (n = 181) and -10.8 kg (-14.2 to -7.4; P < 0.001) for the intention-to-treat population (n = 426). Waist circumference (mean ± standard error of the mean) (-0.13 ± 0.01 cm; P < 0.001), fat mass (-7.8 ± 1.3 kg; P < 0.001) systolic (-11.4 ± 2.0; P < 0.001) and diastolic (-7.0 ± 1.3; P < 0.001) blood pressure, triglycerides (-0.4 ± 0.1; P = 0.004) and plasma glucose (-0.6 ± 0.2; P = 0.001) were significantly reduced. The PCS scale of the SF-36 and all three scales of the three-factor eating questionnaire improved significantly over the 18-month treatment period. All collected data in this study provide evidence that a multidisciplinary treatment programme based on lifestyle modification results in significant weight loss and improvements in cardiometabolic risk factors, quality of life and eating behaviour.

Effect of a high-protein diet on maintenance of blood pressure levels achieved after initial weight loss: the DiOGenes randomized study.

Randomized trials have shown significant blood pressure (BP) reductions after increased protein compared with carbohydrate intake, but the effect on BP maintenance after initial weight loss is unclear. We examined the effect of a high-protein diet on the maintenance of reduced BP after weight loss in 420 overweight adults from the Diet, Obesity and Genes study. After an 8-week weight-loss period (>8% BW), subjects (42±6 years) were randomized to either a high-protein diet (23-28 en% protein) or a lower-protein control diet (10-15 en% protein) for 26 weeks. BMI after weight loss was 30.3±4.3 kg m(-2), BP was 118/73 mm Hg and 28 subjects (6.5%) used antihypertensive agents. Systolic BP during 26 weeks of weight maintenance dietary intervention increased in both treatment groups, but it was 2.2 mm Hg less (95% CI: -4.6 to 0.2 mm Hg, P=0.08) in the high-protein group than in the lower-protein control group. In 191 (pre)hypertensive subjects (baseline systolic BP⩾120 mm Hg), a larger difference was observed (-4.2 mm Hg (-7.7, -0.7), P=0.02). The effect was attenuated after adjustment for initial BP (-3.4 mm Hg (-6.9, -0.03), P=0.048), and after additional adjustment for weight change (-2.7 mm Hg (-6.1, 0.4), P=0.11). Adjustment for 24-h urinary excretion of sodium and potassium did not change the results. Diastolic BP yielded similar results. These findings suggest that a BP reduction after weight loss is better maintained when the intake of protein is increased at the expense of carbohydrates. This effect is partly mediated by body weight.

Weight loss maintenance in overweight subjects on ad libitum diets with high or low protein content and glycemic index: the DIOGENES trial 12-month results.

BACKGROUND: A high dietary protein (P) content and low glycemic index (LGI) have been suggested to be beneficial for weight management, but long-term studies are scarce. OBJECTIVE: The DIOGENES randomized clinical trial investigated the effect of P and GI on weight loss maintenance in overweight or obese adults in eight centers across Europe. This study reports the 1-year results in two of the centers that extended the intervention to 1 year. METHOD: After an 8-week low-calorie diet (LCD), 256 adults (body mass index >27 kg m(-)(2)) were randomized to five ad libitum diets for 12 months: high P/LGI (HP/LGI), HP/high GI (HP/HGI), low P/LGI (LP/LGI), LP/HGI and a control diet. During the first 6 months, foods were provided for free through a shop system and during the whole 12-month period, subjects received guidance by a dietician. Primary outcome variable was the change in body weight over the 12-month intervention period. RESULTS: During the LCD period, subjects lost 11.2 (10.8, 12.0) kg (mean (95% confidence interval (CI))). Average weight regain over the 12-month intervention period was 3.9 (95% CI 3.0-4.8) kg. Subjects on the HP diets regained less weight than subjects on the LP diets. The difference in weight regain after 1 year was 2.0 (0.4, 3.6) kg (P=0.017) (completers analysis, N=139) or 2.8 (1.4, 4.1) kg (P<0.001) (intention-to-treat analysis, N=256). No consistent effect of GI on weight regain was found. There were no clinically relevant differences in changes in cardiometabolic risk factors among diet groups. CONCLUSION: A higher protein content of an ad libitum diet improves weight loss maintenance in overweight and obese adults over 12 months.

Experience and acceptability of diets of varying protein content and glycemic index in an obese cohort: results from the Diogenes trial.

BACKGROUND/OBJECTIVES: To investigate acceptability and tolerability of diets of different protein and glycemic index (GI) content aimed at weight maintenance following a phase of rapid weight loss, as part of a large pan-European dietary intervention trial. SUBJECTS/METHODS: The Diogenes study (www.diogenes-eu.org) consisted of an initial 8-week rapid weight-loss phase (800-1000 kcal/day), followed by a 6-month weight maintenance intervention with five different diets varying in protein and GI content. Measurement of a range of outcomes relating to experience of the Diogenes diets in terms of acceptability, experience and mood were recorded via end of day questionnaires throughout the study. RESULTS: Weight change during the initial weight loss phase weakly, but positively correlated with acceptability of the programme (r range=-0.08 to 0.2, P 0.05, n=685 on four of five dimensions). Success at weight maintenance positively correlated with acceptance of the programme (r range=-0.21 to -0.34, P<0.001, n=540 for all five dimensions). The diets with higher protein content were more acceptable than the low protein (LP) diets, however, no differences between the high vs low GI diets were found concerning acceptability and tolerability. CONCLUSIONS: Results suggest that moderately high protein diets, compared with LP diets, are more acceptable diets for weight control in overweight individuals.

Intake of total protein, plant protein and animal protein in relation to blood pressure: a meta-analysis of observational and intervention studies.

There is growing evidence from epidemiological studies that dietary protein may beneficially influence blood pressure (BP), but findings are inconclusive. We performed a meta-analysis of 29 observational studies and randomized controlled trials (RCTs) of dietary protein and types of protein in relation to BP or incident hypertension, published until January 2012. The analysis included eight cross-sectional studies (n=48 985), four prospective studies (n=11 761) and 17 RCTs (n=1449). A modest inverse association between total protein intake and BP (-0.20 mm Hg systolic (95% CI: -0.39, -0.01) per 25 g (∼1 s.d.)) was found in cross-sectional studies, but not in prospective studies (relative risk of 0.99 (95% CI: 0.96, 1.02)). For RCTs that used carbohydrate as a control treatment, the pooled BP effect was -2.11 mm Hg systolic (95% CI: -2.86, -1.37) for a weighed mean contrast in protein intake of 41 g per day. A non-significant inverse association of -0.52 mm Hg systolic (95% CI: -1.10, +0.05) per 11 g (∼1 s.d.) was found for plant protein in cross-sectional studies, whereas animal protein was not associated with BP. In prospective studies and RCTs, however, the associations of plant protein and animal protein with BP were broadly similar. These findings suggest that increasing the intake of protein at the expense of carbohydrates may have a beneficial effect on BP. The BP effect of specific types of protein remains to be established.

Fatty acid composition of adipose tissue triglycerides after weight loss and weight maintenance: the DIOGENES study.

Fatty acid composition of adipose tissue changes with weight loss. Palmitoleic acid as a possible marker of endogenous lipogenesis or its functions as a lipokine are under debate. Objective was to assess the predictive role of adipose triglycerides fatty acids in weight maintenance in participants of the DIOGENES dietary intervention study. After an 8-week low calorie diet (LCD) subjects with > 8 % weight loss were randomized to 5 ad libitum weight maintenance diets for 6 months: low protein (P)/low glycemic index (GI) (LP/LGI), low P/high GI (LP/HGI), high P/low GI (HP/LGI), high P/high GI (HP/HGI), and a control diet. Fatty acid composition in adipose tissue triglycerides was determined by gas chromatography in 195 subjects before the LCD (baseline), after LCD and weight maintenance. Weight change after the maintenance phase was positively correlated with baseline adipose palmitoleic (16:1n-7), myristoleic (14:1n-5) and trans-palmitoleic acid (16:1n-7t). Negative correlation was found with baseline oleic acid (18:1n-9). Lower baseline monounsaturated fatty acids (14:1n-5, 16:1n-7 and trans 16:1n-7) in adipose tissue triglycerides predict better weight maintenance. Lower oleic acid predicts lower weight decrease. These findings suggest a specific role of monounsaturated fatty acids in weight management and as weight change predictors.

Circulating ACE is a predictor of weight loss maintenance not only in overweight and obese women, but also in men.

BACKGROUND: Circulating angiotensin-converting enzyme (ACE) was identified as a predictor of weight loss maintenance in overweight/obese women of the Diogenes project. OBJECTIVE: To investigate whether ACE acted also as a predictor in men of the Diogenes study and to compare it with that in women. DESIGN: Subjects, who lost ≥ 8% of body weight induced by low-caloric diet in an 8-week weight loss period, were assigned to weight loss maintenance with dietary intervention for 6 months. SUBJECTS: 125 overweight/obese healthy men from eight European countries who completed whole intervention. MEASUREMENTS: Concentrations and activity of serum ACE at baseline and after the 8-week weight loss, in addition to anthropometric and physiological parameters. RESULTS: Serum ACE concentration decreased by 11.3 ± 10.6% during the weight loss period in men. A greater reduction is associated with less body weight regain during the maintenance period (r=0.227, P=0.012). ACE change was able to predict a weight regain ≤ 20% after 6 months, with an odds ratio of 1.59 (95% confidence interval (CI): 1.09-2.33, P=0.016) for every 10% reduction, which was independent of body mass index and weight loss. The prediction power was weaker in men than in women, but without a significant sex difference (P=0.137). In pooled subjects (N=218), the odds ratio was 1.96 (95% CI: 1.46-2.64, P<0.001). CONCLUSIONS: A greater reduction of ACE during weight loss is favorable for weight maintenance in both men and women. This can offer useful information for personalized advice to improve weight loss maintenance. It also confirms the role of ACE in the metabolic pathways of weight regulation.

Predictors of weight loss maintenance and attrition during a 6-month dietary intervention period: results from the DiOGenes study.

There is a need to develop tools to predict individual weight loss maintenance and attrition prognosis. We aimed to identify predictors of weight loss maintenance outcome and attrition in subjects from eight European countries in the DiOGenes project. A total of 932 overweight/obese subjects (body mass index: 27-42 kg m(-2) ) were enrolled in an 8-week low-calorie diet (LCD). The 776 subjects (83%) who achieved at least 8% reduction in their initial body weight were randomized into five dietary arms varying in protein content and glycemic index for a 6-month weight maintenance period. Baseline characteristics, weight loss at weeks 1, 3 and 8 of LCD were assessed as predictors of weight loss maintenance and attrition using multivariate regression and correlation models. The multivariate model showed that the 6-month weight loss maintenance was predicted by: 7.889 - 0.343 × weight loss at week 3 + 1.505 × weight loss at week 8 + 2.422 × gender (0 = male and 1 = female gender) (R(2) = 51%, P = 0.0001). A greater weight loss at week 8 was associated with a lower attrition during the subsequent 6-month dietary intervention period (OR = 0.92, 95% CI: 0.88-0.97, P = 0.001). Furthermore, the men showed an increased likelihood for attrition during the dietary intervention period (OR = 1.54, 95% CI: 1.07-2.20, P = 0.02). A greater weight loss during 8 weeks of LCD and female gender predict better 6-month weight maintenance of weight loss, whereas the baseline characteristics did not predict outcome. Attrition could be strongly predicted by gender and weight loss during LCD.

Developing a methodology for assigning glycaemic index values to foods consumed across Europe.

There is growing evidence that the glycaemic index (GI) of the diet is important with respect to body weight and metabolic disease risk. However, research is limited by the paucity of GI values for commonly consumed carbohydrate-rich foods in European countries. A new methodology has been developed for consistent assignment of GI values to foods across five European databases used in the Diogenes intervention study. GI values were assigned according to five decreasing levels of confidence (1) Measured values for specific foods; (2) Published values from published sources; (3) Equivalent values where published values for similar foods existed; (4) Estimated values assigned as one of three values representing low/medium/high GI ranges and (5) Nominal values assigned as 70, where no other value could be assigned with sufficient confidence. GI values were assigned to 5105 foods. In food records collected at baseline, the contribution to carbohydrate intake of foods assigned levels 1-2 ranged from 16% to 43% depending on country, and this increased to 53-81% including level 3 foods. The degree of confidence to assigned GI values differed across Europe. This standardized approach of assigning GI values will be made available to other researchers to facilitate further investigation into the effects of dietary GI on health.

Initial weight loss on an 800-kcal diet as a predictor of weight loss success after 8 weeks: the Diogenes study.

OBJECTIVE: The purpose of this study was to investigate whether pre-treatment subject characteristics and weight change during the first weeks of a low-calorie diet (LCD) can predict weight loss outcomes at the end of a controlled 8-week weight loss period in overweight and obese adults. SUBJECTS: A total of 932 overweight and obese subjects of both genders were included at eight European centers, and underwent an 8-week LCD period. RESULTS: The weight loss at week 8 was positively correlated with initial body weight (Spearman's rho=0.62), height (rho=0.43), body mass index (rho=0.43), waist (rho=0.48) and hip circumference (rho=0.33), sagittal diameter (rho=0.45), fat mass (rho=0.35) and fat-free mass (rho=0.52), and gender (rho=-0.36) (all P<0.01). In the multivariate regression model, adjusted for center, only initial body weight, early weight loss (week 1) and weight loss at week 3 were significant predictors of weight loss outcome at week 8: weight loss (kg) at week 8=0.09+0.046 x baseline body weight (kg)-0.311 x weight loss (kg) at week 1+1.284 x weight loss (kg) at week 3 (R(2)=68%, P<0.0001). A weight loss of > or =2.6 kg at week 1 during the LCD period was identified as the optimal cut-off predictor for at least 10 kg weight loss at week 8. CONCLUSIONS: This study suggests that initial body weight, early weight loss (week 1) and weight loss at week 3 are predictors of final weight loss during an 8-week LCD, and may be used as early biomarkers of subsequent responses to an LCD diet.

Dietary strategy to manipulate ad libitum macronutrient intake, and glycaemic index, across eight European countries in the Diogenes Study.

The aim of this study was to describe the development and implementation of a multifaceted, low-fat, weight-loss strategy for a Pan-European randomized controlled dietary intervention study, Diogenes. There were 891 families with at least one overweight/obese parent who underwent screening. Eligible, overweight/obese adults followed an 8-week weight-loss phase with a fixed low-energy diet (800 kcal). On attaining weight loss of > or = 8%, families were randomized to a 6- or 12-month low-fat (25-30%E) diet either based on national dietary guidelines or one of four interventions: low protein (LP)/low glycaemic index (LGI), LP/high GI (HGI), high protein (HP)/LGI and HP/HGI. The impact of each diet in preventing weight (re)gain was tested. A points-based system was used to manipulate dietary protein and carbohydrate. Manipulating carbohydrate composition involved substituting foods with a relatively high or low GI. A questionnaire was designed and completed by study investigators, providing feedback on the dietary intervention methods used to inform future interventions. The points system allowed macronutrient manipulations without compromising dietary flexibility or enforcing energy restrictions. Reported centre/participant differences in the ease of implementing the intervention may reflect dietary diversity and personal preferences for specific weight-management strategies. The points system provides a useful starting point for designing improved experimental paradigms for the manipulation of dietary intake in future trials.

Consumption of sugars and body weight.

The role of dietary sugars in the current obesity epidemic is much debated and opposing views can be found in the lay as well as scientific literature. Here we have reviewed the recent scientific literature on consumption of sugars and body weight. Main focus was on three questions: (i) What is the evidence that intake of dietary sugars is associated with higher body weight than intake of non-sugar carbohydrates? (ii) What is the evidence that sugars in liquid form are associated with higher body weight than sugars in solid form? (iii) What is the evidence that diets with a low glycaemic index (GI) or glycaemic load (GL) are associated with lower body weight than diets high in GI or GL? We conclude that (i) there is insufficient evidence that an exchange of sugar for non-sugar carbohydrates in the context of a reduced-fat ad libitum diet or energy-restricted diet results in lower body weights; (ii) observational studies suggest a possible relationship between consumption of sugar-sweetened beverages and body weight, but there is currently insufficient supporting evidence from randomized controlled trials of sufficient size and duration; (iii) at this moment there is insufficient evidence to support a difference between liquid and solid sugar intake in body-weight control and (iv) there is some, although not consistent, evidence for a lower body weight on diets with a lower GL, but the effect is likely to be small. There is currently no convincing evidence for a role of GI independent of GL.

The effect of a low-fat, high-protein or high-carbohydrate ad libitum diet on weight loss maintenance and metabolic risk factors.

BACKGROUND: High-protein (HP) diets are often advocated for weight reduction and weight loss maintenance. OBJECTIVE: The aim was to compare the effect of low-fat, high-carbohydrate (HC) and low-fat, HP ad libitum diets on weight maintenance after weight loss induced by a very low-calorie diet, and on metabolic and cardiovascular risk factors in healthy obese subjects. DESIGN: Forty-eight subjects completed the study that consisted of an energy restriction period of 5-6 weeks followed by a weight maintenance period of 12 weeks. During weight maintenance subjects received maltodextrin (HC group) or protein (HP group) (casein (HPC subgroup) or whey (HPW subgroup)) supplements (2 x 25 g per day), respectively and consumed a low-fat diet. RESULTS: Subjects in the HP diet group showed significantly better weight maintenance after weight loss (2.3 kg difference, P=0.04) and fat mass reduction (2.2 kg difference, P=0.02) than subjects in the HC group. Triglyceride (0.6 mM difference, P=0.01) and glucagon (9.6 pg ml(-1) difference, P=0.02) concentrations increased more in the HC diet group, while glucose (0.3 mM difference, P=0.02) concentration increased more in the HP diet group. Changes in total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, insulin, HOMAir index, HbA1c, leptin and adiponectin concentrations did not differ between the diets. No differences were found between the casein- or whey-supplemented HP groups. CONCLUSIONS: These results show that low-fat, high-casein or whey protein weight maintenance diets are more effective for weight control than low-fat, HC diets and do not adversely affect metabolic and cardiovascular risk factors in weight-reduced moderately obese subjects without metabolic or cardiovascular complications.

The effect of different protein hydrolysate/carbohydrate mixtures on postprandial glucagon and insulin responses in healthy subjects.

OBJECTIVES: To study the effect of four protein hydrolysates from vegetable (pea, gluten, rice and soy) and two protein hydrolysates from animal origin (whey and egg) on glucagon and insulin responses. SUBJECTS/METHODS: Eight healthy normal-weight male subjects participated in this study. The study employed a repeated-measures design with Latin square randomization and single-blind trials. Protein hydrolysates used in this study (pea, rice, soy, gluten, whey and egg protein hydrolysate) consisted of 0.2 g hydrolysate per kg body weight (bw) and 0.2 g maltodextrin per kg bw and were compared to maltodextrin alone. Postprandial plasma glucose, glucagon, insulin and amino acids were determined over 2 h. RESULTS: All protein hydrolysates induced an enhanced insulin secretion compared to maltodextrin alone and a correspondingly low plasma glucose response. A significant difference was observed in area under the curve (AUC) for plasma glucagon between protein hydrolysates and the maltodextrin control drink (P<0.05). Gluten protein hydrolysate induced the lowest glucagon response. CONCLUSIONS: High amino-acid-induced glucagon response does not necessarily go together with low insulin response. Protein hydrolysate source affects AUC for glucagon more profoundly than for insulin, although the protein load used in this study seemed to be at lower level for significant physiological effects.

Short-term beta-adrenergic regulation of leptin, adiponectin and interleukin-6 secretion in vivo in lean and obese subjects.

AIM: Adipose tissue and skeletal muscle are endocrine organs, secreting substances that have been implicated in obesity-related disorders. This study examined short-term beta-adrenergic regulation of circulating leptin, adiponectin and interleukin-6 (IL-6) concentrations and secretion from abdominal subcutaneous adipose tissue and muscle (IL-6) in vivo in lean and obese subjects. METHODS: Systemic concentrations and net fluxes of leptin, adiponectin and IL-6 across abdominal subcutaneous adipose tissue and forearm skeletal muscle (IL-6) were assessed before and during beta-adrenergic stimulation (intravenous isoprenaline infusion) in 13 lean and 10 obese men. RESULTS: Basal circulating leptin concentrations were higher in the obese (p < 0.001), while circulating adiponectin (p = 0.45) and IL-6 concentrations (p = 0.41) were not different between groups. beta-Adrenergic stimulation decreased leptin concentrations in both groups (p < 0.01), but did not reduce net abdominal subcutaneous adipose tissue leptin release. Increased leptin clearance and/or decreased leptin secretion from other fat depots may explain the reduction in leptin concentrations. Adiponectin concentrations remained unchanged during beta-adrenergic stimulation in both groups. beta-Adrenergic stimulation increased IL-6 concentration, which was more pronounced in the obese (p = 0.01 vs. lean). This cannot be explained by increased IL-6 release per unit abdominal subcutaneous adipose tissue and muscle but might be because of the increased fat mass and fat-free mass at whole-body level. CONCLUSIONS: Short-term beta-adrenergic stimulation decreases leptin concentrations, which cannot be explained by reduced net leptin release from abdominal subcutaneous adipose tissue, while it elevates IL-6 concentration partly by increased release from this fat depot and muscle. Finally, beta-adrenergic stimulation has no short-term regulatory role in adiponectin secretion.

A poster-based intervention to promote stair use in blue- and white-collar worksites.

OBJECTIVE: Previous studies have generally shown the effectiveness of prompts to promote stair use in worksites that mainly consist of white-collar workers. The present study tested whether an intervention using prompts is effective in stimulating stair use in two types of worksites: one consisting mainly of white-collar workers and one mainly of blue-collar workers. METHOD: In 2005, elevator and stair use (stair climbing and descent) was monitored in two types of worksites in the Netherlands, namely one office building (n=150 white-collar workers) and one paper factory (n=800 blue-collar workers). The study used a simple time-series design of collecting data in three waves: before, during and after implementation of posters containing prompts stimulating stair use. RESULTS: A total of 6771 choices between stairs and elevator were observed. There was a significant difference between stair use at baseline and during the poster intervention in both types of worksites. There was no worksite-by-intervention interaction, implying that the prompts were equally effective in both types of worksites. After removal of the posters stair use decreased significantly to a level that was not significantly different from baseline. CONCLUSION: Stair use can be positively influenced in both blue- and white-collar workers by a short-term low-cost intervention using prompts on posters.