Thermic effect of food

Thermic effect of food (also commonly known simply as thermic effect when the context is known), or TEF in shorthand, is the increment in energy expenditure above resting metabolic rate due to the cost of processing food for storage and use.1 It is one of the components of metabolism along with the resting metabolic rate, and the exercise component. Another term commonly used to describe this component of total metablisom is the Specific Dynamic Action or SDA. A common number used to estimate the magnitude of the thermic effect of food is about 10% of the caloric intake of a given time period, though the effect varies substantially for different food components. Dietary fat is very easy to process and has very little thermic effect, while protein is hard to process and has a much larger thermic effect.2

Raw celery and grapefruit is often claimed to have negative caloric balance (requiring they take more energy to digest than usable energy received from the food), presumably because the thermic effect is greater than the caloric content, due to the high fibre matrix that must be unraveled to access their carbohydrates. There is no supporting evidence for these claims.

The thermic effect of food is increased by both aerobic training of sufficient duration and intensity and by anaerobic weight training. However, the increase is marginal, amounting to 7-8 cal per hour.1 The primary determinants of daily TEF are the quantity and composition of the food that's ingested.