Association between gastrointestinal phenotypes and weight gain in younger adults: a prospective 4-year cohort study

Background/objectives: Gastrointestinal phenotypes have previously been associated with obesity, however it is unknown if these phenotypes are a cause or a consequence of obesity and weight gain. Our aim was to assess whether these gastrointestinal phenotypes are associated with future weight gain in younger adults. Subjects/methods: At baseline, 126 adult participants under the age of 35 were weighed and underwent measurement of gastrointestinal phenotypes including gastric emptying (GE), gastric volume, satiation, satiety, and gastrointestinal hormones. Patients were reappraised after median 4.4 years unless, during the period of follow-up, they participated in a formal weight loss program, received obesity-weight loss interventions, or developed a health condition likely to affect weight. Participants were dichotomized into two groups for each phenotype at the median of each phenotype. Results: In total, 60 participants met criteria for inclusion and were evaluated after a median of 4.4 years [IQR: 3.5–5], 36 participants were excluded due to conditions that would abnormally affect weight during study period including pregnancy and weight loss treatment, and 30 participants were lost to prospective follow-up. Faster GE was significantly associated with weight gain. Those with faster GE at baseline (n = 30) gained a median of 9.6 kg [3.1–14.9] compared with those with slower GE at baseline (n = 30) who gained a median of 2.8 kg [−4.6 to 9.2] (p = 0.03), over the follow-up period. There was no association between the other phenotypes and weight gain. Conclusions: In adults ≤35 years old, faster gastric emptying is associated with significantly increased weight gain over the medium term. This provides supportive evidence for the role of gastric emptying in weight gain and development of obesity.