What does the thermic effect of food (TEF) refer to?

The thermic effect of food (TEF) refers to the increase in metabolic rate after eating. This phenomenon occurs because the body expends energy to digest, absorb, and process the nutrients from food. When you consume a meal, your body's metabolism ramps up to help break down the food and utilize its components for energy, repair, and storage. This process involves various activities, including the secretion of digestive enzymes, movement of the gastrointestinal tract, and the absorption of nutrients into the bloodstream, all of which require energy and thus elevate metabolic rate temporarily.

TEF is typically quantified as a percentage of the caloric content of the food consumed, with protein generally having the highest thermic effect, followed by carbohydrates and then fats. This is relevant for understanding overall energy expenditure, metabolic health, and weight management.

The other options provided do not accurately describe TEF. The storage of excess calories as fat relates to energy balance rather than the immediate metabolic response following food intake. The breakdown of fatty acids during fasting pertains to energy mobilization in the absence of food consumption. Lastly, the energy expended during physical activity involves exercise and movement, which is a separate component of total daily energy expenditure and not part of the thermic effect.