The effect of long-term caloric restriction and dietary fibre on energy expenditure, acylated ghrelin, total ghrelin and adipose tissue hormones

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Dietary factors may influence the efficiency of weight loss and subsequent weight maintenance. Ghrelin, a peptide hormone secreted primarily in the stomach and endogenous ligand of growth-hormone secretague receptor, has two major molecular forms: acylated and desacyl ghrelin. Ghrelin acts to maintain body weight in a steady state and both molecular forms have counteracting roles with respect to energy balance. Short-term studies have shown that dietary fibre decreases postprandial acylated ghrelin, but its role in long-term caloric restriction remains unclear. Other hormones secreted by adipose tissue are also involved in energy balance such as leptin, resistin and adiponectin, mainly via insulin action. In the present project, a randomized controlled long-term caloric restriction trial is conducted over a 12 month period to investigate the metabolic effects of caloric restriction (CR) to either, a diet low in fat or low in glycemic index and how they are modulated by dietary fibre. Overweight subjects (n = 60) will be randomly assigned to either, a diet low in fat or low in glycemic index. Additionally, half of each group will take a fibre supplement (20 g/d). The aim of the study is to investigate whether dietary fibre (1) suppresses ghrelin increase during weight loss, (2) has beneficial effects on adiponectin, leptin and resistin levels and (3) prevents weight regain. In a second trial, the effects of CR for 6 months to either, 70 or 80 % of weight maintenance energy requirements on total energy expenditure (TEE), resting metabolic rate and acylated and desacyl ghrelin is examined in overweight subjects (n = 80). This study will be the first long-term trial with repeated measures of TEE focussing on ghrelin secretion and will be important for the understanding of weight regulation and prevention of weight regain. (1560 characters).