The influence of cigarette smoking and food intake on resting energy expenditure (REE) was investigated. Fifteen smokers were presented, over four days, with cigarette consumption, food consumption, the consumption of both cigarettes and food, and neither cigarettes nor food consumption. Results indicated that both food and cigarette smoking increased REE and food increased REE considerably more than smoking cigarettes (17.1 vs 7.5 percent). The combination of the two was less than additive (24.1 percent). The results may aid in elucidating the mechanisms that contribute to a lowered body weight in smokers.