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

Barbara Livingstone, Tamsyn L. Redpath, Fathimath Naseer, Adele Boyd, Melanie Martin, Graham Finlayson, Alexander D Miras, Zsolt Bodnar , David Kerrigan, Dimitri J. Pournaras, CW Le Roux, Alan C. Spector, RK Price

Research output: Contribution to journalArticlepeer-review


Lack of robust research methodology for assessing ingestive behaviour has impeded clarification of the mediators of food intake following gastric bypass (GBP) surgery.

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.

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.

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.

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 surgery.

Clinical Trial Registry Number: NCT03113305 (
Original languageEnglish
Article numberepub
JournalJournal of Nutrition
Early online date23 Jul 2022
Publication statusPublished - 23 Jul 2022


  • gastric bypass


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