Food intake following gastric bypass surgery: patients eat less but do not eat differently.

BACKGROUND: Lack of robust research methodology for assessing ingestive behaviour has impeded clarification of the mediators of food intake following gastric bypass (GBP) surgery. OBJECTIVE: To evaluate changes in directly measured 24hr energy intake (EI), energy density (ED) (primary outcomes), eating patterns and food preferences (secondary outcomes) in patients and time matched weight-stable comparator participants. DESIGN: Patients (n = 31,77% female, BMI 45.5±1.3) and comparators (n = 32, 47% female, BMI 27.2±0.8) were assessed for 36hr under fully residential conditions at baseline (1-mo pre-surgery) and at 3- and 12-mo post-surgery. Participants had ad libitum access to a personalised menu (n = 54 foods) based on a 6 macronutrient mix paradigm. Food preferences were assessed by the Leeds Food Preference Questionnaire. Body composition was measured by whole-body dual-energy x-ray absorptiometry. RESULTS: In the comparator group there was an increase in relative fat intake at 3-mo post-surgery, otherwise no changes were observed in food intake or body composition. At 12-mo post-surgery, patients lost 27.7±1.6% of initial body weight (p<0.001). The decline in EI at 3-mo post-surgery (-44% from baseline, P<0001)) was followed by a partial rebound at 12-mo (-18% from baseline) but at both times dietary ED and relative macronutrient intake remained constant. The decline in EI was due to eating the same foods as consumed pre-surgery and by decreasing the size (g, MJ), but not the number, of eating occasions. In patients, reduction in explicit liking at 3-mo (-11.56±4.67, P = 0.007) and implicit wanting at 3- (-15.75±7.76, P = 0.01) and 12-mo (-15.18±6.52, P = 0.022) for sweet foods was not matched by reduced intake of these foods. Patients with the greatest reduction in ED post-surgery reduced both EI and preference for sweet foods. CONCLUSION: After GBP patients continue to eat the same foods but in smaller amounts. These findings challenge prevailing views about the dynamics of food intake following GBP ...