The Effect of Wholegrain on Appetite:Short- and Long-Term Effects and the Potential Role of Colonic Fermentation

Background: Wholegrain consumption is suggested to improve short-term appetite sensation. This may occur immediately after wholegrain intake but also after a second meal. The latter may potentially be mediated by short-chain fatty acids (SCFA) that are generated during colonic fermentation of wholegrain components. Little is, however, known how regular wholegrain intake influences appetite sensation. Hypothetically, an increase in satiety-inducing gut hormones, due to steady colonic fermentation upon regular wholegrain intake, may lead to an improvement of the overall appetite sensation. In the long run, regular wholegrain intake may also reduce body weight due to reoccurring short- and long-term effects on appetite. Aim: This PhD thesis investigates the effects of selected wholegrain products on appetite after a second meal, as well as the effects of sustained wholegrain intake on overall appetite sensation with special attention to the role of colonic fermentation. Further, the impact of regular wholegrain intake on body weight is investigated. Methods: In a second meal study we studied the effects of two coarse wholegrain rye evening meals on subjective appetite after a standardized breakfast and on ad libitum energy intake at lunch at the subsequent day compared to white wheat bread. In a human intervention study we investigated the effects of 8-week ad libitum consumption of a mixed wholegrain diet on appetite after a standardized, non-wholegrain breakfast, on ad libitum energy intake at a subsequent lunch, and on body weight compared to 8-week refined grain consumption. Furthermore, in a crosssectional study we studied the associations between habitual wholegrain intake and appetite after a standardized, non-wholegrain breakfast, ad libitum energy intake at lunch and body weight. In the three studies we approximated colonic fermentation by measuring the excretion of hydrogen in the breath. Moreover, we de