Energy expenditure of genuine laughter

Objective: To measure energy expenditure (EE) and heart rate (HR) during genuine laughter. Design: Experimental trial of viewing film clips in four cycles either intended to evoke laughter (humorous - 10 min) or unlikely to elicit laughter (not humorous -5 min) under strictly controlled conditions of a whole-room indirect calorimeter equipped with audio recording system. Participants: Forty five adult friend dyads in either same-sex male (n = 7), same- sex female (n = 21) and mix-sex male-female (n = 17); age 18-34 years; body mass index 24.7 +/- 4.9 (range 17.9-41.1). Measurements: Energy expenditure in a whole-room indirect calorimeter, HR using Polar HR monitor. Laugh rate, duration and type from digitized audio data using a computerized system and synchronized with HR and EE results. Results: Laughter EE was 0.79 +/- 1.30 kJ/min (0.19 +/- 0.31 kcal/min) higher than resting EE (P < 0.001, 95% confidence interval = 0.75-0.88 kJ/min), ranging from -2.52 to 9.67 kJ/min (-0.60-2.31 kcal/min). Heart rate during laughter segments increased above resting by 2.1 +/- 3.8 beats/min, ranging from -7.6 to 26.8 beats/min. Laughter EE was correlated with HR (r(s) = 0.250, P < 0.01). Both laughter EE and HR were positively correlated with laughter duration (r(s) = 0.282 and 0.337, both P < 0.001) and rate (r(s) 0.256 and 0.298, both P < 0.001). Conclusion: Genuine voiced laughter causes a 10-20% increase in EE and HR above resting values, which means that 10-15 min of laughter per day could increase total EE by 40-170 kJ (10-40 kcal).