People with obesity have different appetitive responses to stimuli compared to people without obesity. For example, people with obesity have a blunted postprandial ghrelin ('hunger' hormone) response, lower glucagon-like peptide 1 (GLP-1) and peptide-YY (PYY; associated with satiety) compared to people without obesity. Given the favorable effects of exogenous ketones on appetite previously observed in healthy adults of normal body weight, it is possible that these supplements can alter appetite hormones in a manner that may closer match that observed in people without obesity. To explore this research question, investigators will conduct a randomized single-blind cross over study to characterize appetite and dietary intake after ingestion of an exogenous ketone supplement within adults with obesity (compared a control condition without exogenous ketones) and compared to adults without obesity. The research team will also explore differences in postprandial energy expenditure and fuel utilization. Twenty-two healthy young- and middle-aged adults will be included (up to n=26 enrolled). In addition to a baseline visit to measure body composition, participants will undergo two 4.5-hour study visits, one of which will include a ketone diol supplement and one will have a placebo. Participants will be given a 1-day run-in diet prior to each study day to support energy balance. On each study day visit, participants will undergo a resting metabolic rate test (indirect calorimetry) followed by a fasting appetite rating and blood sample collection. Participants will then be provided with a standard breakfast meal (one with the ketone supplement and one with placebo). Appetite ratings and blood sample collection will be repeated 60, 120, and 180 minutes after the meal. Indirect calorimetry will be completed after the 30, 90, and 150 minute assessments. After the 180-minute timepoint, participants will be provided with a buffet-like lunch meal with instructions to eat as much or as little as they would like to determine ad libitum dietary intake at a single meal. To assess free-living ad libitum dietary intake, participants will receive 1.5 days of food boxes tailored to their preferences, with uneaten food returned at the end of the 1.5-day period. This study will be the first to assess the impact of exogenous ketones on appetite in obesity and would help inform future weight loss intervention trials.
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Acylated ghrelin area under the curve (AUC)
Timeframe: 3 hours