Several studies have linked higher intake of dietary fibre (DF) to improved management of body weight^{(Reference Kendall, Esfahani and Sanders1,Reference Higgins2)} . Appetite studies are frequently conducted only in lean, healthy control subjects and so conclusions derived from normal weight subjects might not be directly transferable to overweight /obese subjects^{(Reference Bodinham, Frost and Robertson3)}. The aim of this investigation was to compare the effect of ingestion of 48 g of RS on subjective (appetite ratings) and objective (ad libitum energy intake) markers of eating behavior and postprandial changes in plasma glucose, insulin, C-peptide and GLP-1 between lean and overweight /obese healthy males.

Thirty healthy, male subjects participated in this investigation. All subjects were aged between 18–32 y; 20 of normal weight (BMI 20.1–24.7 kg/m²) and 10 overweight/obese (BMI 28–37 kg/m²). In two visits, subjects consumed either the RS supplement or placebo, both of which were incorporated into separate breakfast and lunch meals giving a total of 48 g DF or 0 g DF respectively. Subjects recorded their appetite ratings subjectively using visual analogue scales (VAS) every 30 min, while energy intakes were assessed quantitatively from an ad libitum dinner for 7 hours in addition to 24-hour diet diaries. Postprandial blood glucose, insulin, C-peptide and GLP-1 responses were also measured.

We found a significant effect of BMI group on appetite sensation with overweight individuals rating less hunger and prospective food consumption and was almost significant for fullness compared with the lean group (p = <0.001, p = 0.057) respectively. However, no significant differences in energy intake at the ad libitum test meal or over a 24 hour period were found. Although glucose and insulin responses were not significantly different after RS or the placebo between both group, obese group had higher insulin concentration and higher C-peptide (time*group, p < 0.001). The C-peptide to insulin ratio also was significantly higher in the obese group compared with the lean group (p < 0.001). Our results showed that postprandial plasma GLP-1 concentrations were lower in the obese group (p = 0.009).

In conclusion, the observed differences after consumption of RS in the current study may play a role in body weight regulation in groups with varied BMI. Future research is needed to understand the mechanisms for the variability in pre- and post-prandial glycaemic and hormonal responses in individuals with different body mass. Understanding these factors could help in the development of new treatments for obesity.