Effects of Caffeine and Coffee on Resting Metabolic Rate, Comparing Normal Weight Men to Obese Men

Background. The prevalence of obesity has increased in the last two decades. To maintain body weight energy expenditure (EE) should be equal to energy intake (EI). A low EE predisposes individuals to weight gain and to obesity that can also results from low resting metabolic rate (RMR). Caffeine (Caf) is an active food ingredient and is widely consumed globally, and has an important impact on energy balance. Caf reduces appetite (EI) and increases EE, thus, Caf has a potential role in body weight reduction. Caf causes higher total daily energy expenditure (TDEE) in normal weight (NW) people compared to obese (OW). Moreover Caf is linked to decreased fat oxidation in OW. There are differences between OW and NW in Caf pharmacokinetics, but no differences reported between NW and OW females in its effects on RMR. There is a gender difference in the influence of Caf on metabolism. The investigators are aware of no previous studies which compared the effect of Caf on the RMR of NW and OW men. Objectives. 1) To compare the effect of Caf and coffee on resting metabolic rate (RMR) values in healthy normal-weight (NW) men and overweight (OW) men. 2) To develop Caf intake frequency questionnaire (in Hebrew) Hypothesis. RMR values will be higher and respiratory exchange ratio (RER) values will be lower in NW compared to the values measured in OW men. Methods. 33 men (16 NW and 17 OW) were reported to the laboratory on 4 separate occasions (placebo, Caf tablets, coffee and decaffeinated coffee). During the lab sessions they were undergo complete anthropometric measurements and RMR measured (one of the study conditions) using indirect calorimetry. Additionally, respiratory exchange ratio (RER) which is calculated as the ratio between CO2 production (VCO2) and O2 consumption (VO2) (VCO2/VO2), blood pressure and heart rate (HR) response recorded. The importance of this study is that the results will contribute to the scientific basis of weight control and health interventions p