Habitual meal frequency and energy intake regulation in partially temporally isolated men

Department of Human Biology, University of Maastricht, Maastricht, The Netherlands. [email protected] OBJECTIVE: Assessment of a possible relationship between habitual as well as manipulated meal frequency, blood glucose pattern, macronutrient- and energy intake (EI), and energy intake regulation in partially temporally isolated men. DESIGN: A partially temporally isolated within-subject design assessing energy intake regulation in spite of intervention. Intervention consisted of manipulating meal frequency by offering iso-energetic (1 MJ) preloads high in fat or carbohydrate (CHO), with the same energy density. We have previously shown that after a high-CHO preload, inter-meal-interval was 1 h, while after a high-fat preload intermeal-interval was 2 h. SUBJECTS: Twenty healthy young (18-31 y) normal weight (body mass index (BMI): 22.8+/-1.9 kg/m(2)) men. MEASUREMENTS: On two separate days, each after a different preload: subsequent subjects' responses to the preload, eg manipulated meal frequency; continuous blood glucose levels and blood glucose patterns: macronutrient composition of food intake; EI; appetite ratings; and taste perception. From controlled 3-day food intake diaries: habitual meal frequency; EI; and macronutrient-intake. RESULTS: Accuracy of energy intake regulation is expressed as minimizing the difference in energy intake, despite intervention. The difference in 24 h EI on the two test days after the preloads (r(2)=0.56; P<0.001) was a function of habitual meal frequency. Variation in energy intake was primarily explained by habitual meal frequency (r(2)=0.76; P<0.0001). Adding macronutrient composition and number of blood glucose declines to this increased the explained variation to 86 and 96%, respectively. Percentage energy from CHO or from fat explained the variation in habitual meal frequency (r(2)=0.84; P<0.0001). Adding the total number of blood-glucose declines to this increased the explained variation to 88%, and adding average baseline blood glucose levels, sweetness perception and hunger suppression during preload consumption increased the explained variation to 91%. Manipulated meal frequency was related to habitual meal frequency (r(2)=0.86; P<0.0001) and was a function of the number of transient and dynamic blood glucose declines (r(2)=0.74; P<0.0001). CONCLUSION: Habitual meal frequency is of greater significance in energy intake regulation in healthy young men than manipulated meal frequency. Healthy young men with a high habitual meal frequency showed lower 24 h EI, and a smaller difference in EI after macronutrient specific preloads, compared to those with a low habitual meal frequency, thus showing a more accurate energy intake regulation. Habitual meal frequency is based upon a cluster of related factors including macronutrient composition of the food, sweetness perception, hunger suppression, blood glucose declines and average baseline blood glucose levels. Publication Types: Clinical Trial Randomized Controlled Tria

Circulating glucose levels modulate neural control of desire for high-calorie foods in humans

Obesity is a worldwide epidemic resulting in part from the ubiquity of high-calorie foods and food images. Whether obese and nonobese individuals regulate their desire to consume high-calorie foods differently is not clear. We set out to investigate the hypothesis that circulating levels of glucose, the primary fuel source for the brain, influence brain regions that regulate the motivation to consume high-calorie foods. Using functional MRI (fMRI) combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and behavioral measures of interest in food, we have shown here that mild hypoglycemia preferentially activates limbic-striatal brain regions in response to food cues to produce a greater desire for high-calorie foods. In contrast, euglycemia preferentially activated the medial prefrontal cortex and resulted in less interest in food stimuli. Indeed, higher circulating glucose levels predicted greater medial prefrontal cortex activation, and this response was absent in obese subjects. These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity. Strategies that temper postprandial reductions in glucose levels might reduce the risk of overeating, particularly in environments inundated with visual cues of high-calorie foods

The effect of low carbohydrate on energy metabolism.

OBJECTIVE: To investigate whether low-carbohydrate diets are efficient for reduction of body weight and through which mechanism. DESIGN: A couple of studies using low-carbohydrate diets in the treatment of obesity are reviewed. Mechanisms for explaining the reduced appetite are described in relation to knowledge on regulation of appetite for fat and carbohydrate. RESULTS: Studies with low-carbohydrate diets demonstrate a rapid weight loss, being more pronounced after 3 and 6 months compared to low-fat diets. After 12 months there is no difference between the low-carbohydrate and the conventional low-fat diet on weight loss. Both diets lead to improvements in risk factors for coronary heart disease, the low-carbohydrate diet leading to a greater decrease in serum triglycerides and increase in HDL cholesterol compared to the low-fat diet. Blood pressure, insulin sensitivity and LDL cholesterol were improved to a similar degree by the two diets. The mechanism for the rapid weight loss with the low-carbohydrate diet is a suppressed appetite, first through the high-protein content of the diet, second through the ketogenic nature of the diet with satiety signals for fat being active and third through the absence of hunger-promoting carbohydrate components like sucrose and/or fructose. CONCLUSION: A rapid initial weight loss occurs with a low-carbohydrate diet due to a suppressed appetite. There is as yet no indication of an increased metabolic rate and an increased thermogenesis by the low-carbohydrate diet. The safety and efficacy of low-carbohydrate diets have to await further studies