Caffeine Transiently Affects Food Intake at Breakfast

Background: Caffeine is frequently added to dietary supplements with claims it facilitates weight loss. Objective: The purpose of this study was to test the hypothesis that caffeine administration reduces laboratory and free-living food intake by reducing appetite and that these effects vary by body mass index (BMI). Participants/setting: Fifty adults aged 18 to 50 years completed the study (42% male). Exclusion criteria included no previous experience with caffeine, previous adverse event following caffeine consumption, taking any medications or having a medical condition contraindicating caffeine or stimulant consumption or affecting appetite or eating, and reported tobacco use within the past 6 months. Design and intervention: Participants visited the laboratory on four separate occasions to complete a double-blind, placebo-controlled, randomized, crossover study. On the first three visits, participants consumed a beverage containing 0, 1, or 3 mg/kg caffeine (order randomized). Thirty minutes later, participants consumed a buffet breakfast, ad libitum. After leaving the laboratory, participants completed hourly appetite assessments and dietary habit books until midnight or bedtime. The fourth session consisted of questionnaires, debriefing, and compensation. Main outcome measures: Total and macronutrient intake and appetite sensations in and out of the laboratory were measured. Statistical analyses performed: Intake data were analyzed using mixed analysis of covariance (ANCOVA). Appetite sensations were analyzed using repeated measures mixed ANCOVA. Results: Total laboratory energy intake was lower (∼10%) after 1 mg/kg caffeine (650.4±52.2 kcal at 1 mg/kg; 721.2±63.2 at 0 mg/kg; 714.7±79.0 at 3 mg/kg) (P=0.046). In the laboratory, appetite sensations were not significantly different by caffeine treatment. Out of the laboratory, neither total intake nor appetite was significantly different by caffeine treatment. There were no significant interactions between caffeine treatment and BMI on intake and appetite sensations in or out of the laboratory. Conclusions: These results suggest caffeine has weak, transient effects on energy intake and do not support caffeine as an effective appetite suppressant.