We examined the effect of intravenously infused glucagon-like peptide 1 (GLP-1) on subjective appetite sensations after an energy-fixed breakfast, and on spontaneous energy intake at an ad libitum lunch. 20 young, healthy, normal-weight men participated in a placebo-controlled, randomized, blinded, crossover study. Infusion (GLP-1, 50 pmol/ kg.h or saline) was started simultaneously with initiation of the test meals. Visual analogue scales were used to assess appetite sensations throughout the experiment and the palatability of the test meals. Blood was sampled throughout the day for analysis of plasma hormone and substrate levels. After the energy-fixed breakfast, GLP-1 infusion enhanced satiety and fullness compared with placebo (treatment effect: P < 0.03). Furthermore, spontaneous energy intake at the ad libitum lunch was reduced by 12% by GLP-1 infusion compared with saline (P = 0.002). Plasma GLP-1, insulin, glucagon, and blood glucose profiles were affected significantly by the treatment (P < 0.002). In conclusion, the results show that GLP-1 enhanced satiety and reduced energy intake and thus may play a physiological regulatory role in controlling appetite and energy intake in humans.

Milk and dairy products: good or bad for human health? An assessment of the totality of scientific evidence

Background: The role of glycemic index (GI) in appetite and body-weight regulation is still not clear. Objective: The objective of the study was to investigate the long-term effects of a low-fat, high-carbohydrate diet with either low glycemic index (LGI) or high glycemic index (HGI) on ad libitum energy intake, body weight, and composition, as well as on risk factors for type 2 diabetes and ischemic heart disease in overweight healthy subjects. Design: The study was a 10-wk parallel, randomized, intervention trial with 2 matched groups. The LGI or HGI test foods, given as replacements for the subjects' usual carbohydrate-rich foods, were equal in total energy, energy density, dietary fiber, and macronutrient composition. Subjects were 45 (LGI diet: n = 23; HGI diet: n = 22) healthy overweight [body mass index (in kg/m²): 27.6 ± 0.2] women aged 20–40 y. Results: Energy intake, mean (± SEM) body weight (LGI diet: −1.9 ± 0.5 kg; HGI diet: −1.3 ± 0.3 kg), and fat mass (LGI diet: −1.0 ± 0.4 kg; HGI diet: −0.4 ± 0.3 kg) decreased over time, but the differences between groups were not significant. No significant differences were observed between groups in fasting serum insulin, homeostasis model assessment for relative insulin resistance, homeostasis model assessment for β cell function, triacylglycerol, nonesterified fatty acids, or HDL cholesterol. However, a 10% decrease in LDL cholesterol (P < 0.05) and a tendency to a larger decrease in total cholesterol (P = 0.06) were observed with consumption of the LGI diet as compared with the HGI diet. Conclusions: This study does not support the contention that low-fat LGI diets are more beneficial than HGI diets with regard to appetite or body-weight regulation as evaluated over 10 wk. However, it confirms previous findings of a beneficial effect of LGI diets on risk factors for ischemic heart disease.

Aims: The PREVIEW lifestyle intervention study ( ClinicalTrials.gov Identifier: NCT01777893) is, to date, the largest, multinational study concerning prevention of type‐2 diabetes. We hypothesized that the initial, fixed low‐energy diet (LED) would induce different metabolic outcomes in men vs women. Materials and methods: All participants followed a LED (3.4 MJ/810 kcal/daily) for 8 weeks (Cambridge Weight Plan). Participants were recruited from 8 sites in Europe, Australia and New Zealand. Those eligible for inclusion were overweight (BMI ≥ 25 kg/m ² ) individuals with pre‐diabetes according to ADA‐criteria. Outcomes of interest included changes in insulin resistance, fat mass (FM), fat‐free mass (FFM) and metabolic syndrome Z‐score. Results: In total, 2224 individuals (1504 women, 720 men) attended the baseline visit and 2020 (90.8%) completed the follow‐up visit. Following the LED, weight loss was 16% greater in men than in women (11.8% vs 10.3%, respectively) but improvements in insulin resistance were similar. HOMA‐IR decreased by 1.50 ± 0.15 in men and by 1.35 ± 0.15 in women (ns). After adjusting for differences in weight loss, men had larger reductions in metabolic syndrome Z‐score, C‐peptide, FM and heart rate, while women had larger reductions in HDL cholesterol, FFM, hip circumference and pulse pressure. Following the LED, 35% of participants of both genders had reverted to normo‐glycaemia. Conclusions: An 8‐week LED induced different effects in women than in men. These findings are clinically important and suggest gender‐specific changes after weight loss. It is important to investigate whether the greater decreases in FFM, hip circumference and HDL cholesterol in women after rapid weight loss compromise weight loss maintenance and future cardiovascular health.

Expansion of the fat stores has been proposed as a prerequisite for increasing fat oxidation in response to a high-fat diet in individuals with a predisposition to obesity. In a cross-sectional design we measured 24-h substrate oxidations on a standardized diet in 38 overweight or obese and 35 nonobese women. Fat oxidation (g/d) was mainly a function of total energy requirements (r = 0.71, P < 0.0001). To account for this we used for further analysis oxidative fat energy (%), a counterpart to dietary fat energy (%). After differences in fat energy of consumed food (%), age, and 24-h energy balance were adjusted for, obese women had higher oxidative fat energy than did nonobese women [40.2% (37.8–42.6) vs 36.0% (33.6–38.5), P < 0.02]. Adjusted oxidative fat energy (%) increased with increasing size of fat mass (r = 0.31, P < 0.01). This relation suggests that a 10-kg change in fat mass may be caused by a change in dietary fat energy of ≥ 1.6% (0.4–2.7%). The study supports the concept that in susceptible individuals the expansion of fat stores is a prerequisite to increase the oxidative fat energy to an amount commensurate with a high percentage of dietary fat energy.

The applicability of the glycaemic index (GI) in the context of mixed meals and diets is still debatable. The objective of the present study was to investigate the predictability of measured GI in composite breakfast meals when calculated from table values, and to develop prediction equations using meal components. Furthermore, we aimed to study the relationship between GI and insulinaemic index (II). The study was a randomised cross-over meal test including twenty-eight healthy young men. Thirteen breakfast meals and a reference meal were tested. All meals contained 50 g available carbohydrate, but differed considerably in energy and macronutrient composition. Venous blood was sampled for 2 h and analysed for glucose and insulin. Prediction equations were made by regression analysis. No association was found between predicted and measured GI. The meal content of energy and fat was inversely associated with GI (R²0·93 and 0·88, respectively;P<0·001). Carbohydrate content (expressed as percentage of energy) was positively related to GI (R²0·80;P<0·001). Using multivariate analysis the GI of meals was best predicted by fat and protein contents (R²0·93;P<0·001). There was no association between GI and II. In conclusion, the present results show that the GI of mixed meals calculated by table values does not predict the measured GI and furthermore that carbohydrates do not play the most important role for GI in mixed breakfast meals. Our prediction models show that the GI of mixed meals is more strongly correlated either with fat and protein content, or with energy content, than with carbohydrate content alone. Furthermore, GI was not correlated with II.