I’ve been told this so many times, and it feels so right it should be true: your metabolic rate while watching television is lower than when you are unconscious. It should be true, but it isn’t

Buchowski MS, Sun M. (1996). Energy expenditure, television viewing and obesity.
International Journal of Obesity Related Metabolism Disorders. 1996 Mar;20(3):236-44.
Abstract: OBJECTIVE: To measure energy expenditure (EE) of television viewing, sitting, and resting and duration of self-selected television viewing in obese and non-obese men and women. DESIGN: Cross-over randomized study consisting of two separate 24-h stays in a whole-room indirect calorimeter. SUBJECTS: 123 obese and non-obese healthy men and women (age: 38 +/- 9, BMI: 29.4 +/- 7.9) MEASUREMENTS: Rates of energy expenditure during resting (RMR), sitting (EEsit) and television viewing (EEtv) using indirect calorimetry technique on two separate 24-h stays in a whole-room indirect calorimeter. Physical activities and work of body movements during these periods using a large force platform system located inside the calorimeter. RESULTS: Rates of EE for television viewing, adjusted for differences in body composition were 18% higher than resting metabolic rate (RMR), but similar to rates of other sedentary activities. There were no significant differences between obese and non-obese subjects in metabolic rates during resting, television viewing, and other sedentary activities. Average time of self-selected television viewing was significantly greater in obese than in non-obese subjects and also in women than in men. CONCLUSION: EE rate for television viewing in adults is higher than RMR and similar to other sedentary activities. Obese adults choose television viewing as a form of leisure activity more often than non-obese individuals and as a result they could significantly reduce other forms of physical activities and total daily EE.