The thermic effect of food is one of three factors contributing to the total metabolic rate of the daily calories burned, the other two being our basal metabolic rate (BMR) also known as our resting metabolic rate (RMR) as well as our level of physical activity. A common estimate of thermic effect of food is that it accounts for an energy expenditure equal to 10% of our daily calorie intake. The relationship between eating speed and the thermic effect of food remains unclear.
Researchers investigated the difference in the thermic effect of food when meals containing the same amount of energy were eaten in 5?min (fast eating) or 15?min (regular eating). Subjects were nine non-obese young women. Following a 350?kcal (1464?kJ) meal, energy expenditure and autonomic nervous system activity were measured. The thermic effect of food for the 15-min period after the start of eating with fast eating was significantly lower than with regular eating. Fast eating may reduce the thermic effect of food, potentially because a decrease in mastication frequency decreases sympathetic nervous system activation. Another interesting finding was that the thermic effect of food was correlated with the chewing and frequency. This led the researchers to suggest that a lowered thermic effect of food from eating faster was because a decrease in chewing frequency resulted in decreased sympathetic nervous system activity. As such, there is less need for energy providing processes such as thermic effect of food.
The moral of the story is that people need to slow down when they eat their food, as pointed out by this study the thermic effect of food was less when people ate fast so a meal should be eaten over a 15 minute period if not longer.
Toyama K, Zhao X, Kuranuki S, Oguri Y, Kashiwa Kato E, Yoshitake Y, Nakamura T. The effect of fast eating on the thermic effect of food in young Japanese women. Int J Food Sci Nutr. 2015 Jan 22:1-8.
Robbie Durand has been in the sports supplement and bodybuilding industry for 15 years. He has contributed to many national magazines and web sites. He has an M.A. in exercise physiology from Southeastern University and a B.A. in Dietetics from Louisiana State University.