Effect of contingent hunger state on development of appetite for a novel fruit snack

Eating more fruit can reduce risk of cancer and cardiovascular disease. Understanding barriers to this behaviour is critical for strategies to encourage it. We addressed the question whether the level of hunger at which fruit is eaten would influence the development of appetite for fruit. Half the participants were asked to eat a pair of novel fruit snacks (dried fruit bar; 50 kcal each) exclusively when hungry (at least 3 hours since last eating), and half to eat them exclusively when full (20-30 minutes after a meal), twice a day for one week. Rated appetite for the bars, and ad-libitum intake, were measured when hungry and full, on 2 days prior to, and 2 days after this week. Compliance was assessed from dietary diaries. Thirty participants (22 women, 8 men) completed the study satisfactorily. For the group eating the fruit bars only when hungry (hungry-trained), intake increased after the week, but only when full at the time of testing. Other measures of appetite for this group were unaffected, with the exception of a reduced desire to eat the bars when tested hungry. Ranked preference for the trained flavour increased exclusively among hungry-trained subjects, but only for those who had reported their preferred snack food to be fruit. No change in any measure was found for the group eating the fruit bars exclusively when full. The results suggest the hungry-trained group learnt that the bars lacked strong satiation, thus allowing greater intake when full (learnt desatiation). For the same reason, however, the prospect of eating the bars when mildly hungry lost its appeal. Eating fruit between meals may not encourage snacking on fruit, unless hunger is absent at the time of consumption.