THERMIC EFFECT OF FOOD
Thermic effect of food (TEF) is defined as: the increase in metabolic rate after ingestion of a meal.
There is not a TON of research on the topic of TEF, but there is a good enough amount to draw some conclusions. Most of the articles I was finding were from the 1990s, so some more present day research would be interesting to see. Overall there are definitely a few clear conclusions we can draw- even if the research is slightly outdated. TEF is significantly higher after consuming large meals less frequently, as opposed to small meals more frequently, there is a significant link between TEF and fullness sensation, and thermic effect varies by macronutrient.
A study was conducted looking at the effects of meal size and TEF in seven healthy normal-weight young women (1). Each volunteer consumed in random order one of two identical meals [750 kcal, 54.5% carbohydrate, 14.0% protein, 31.5% fat]. One meal was taken over 10 min [large meals LM)] whereas the other was taken in six equal portions of (125 kcal) at 30-min intervals over a 3-h period [small meals (SM)]. Metabolic rate was measured for 1 h before and every 30 min after the meal started for 5 h. TEF was significantly higher in the LM day than in the SM day. The researchers concluded that the pattern in which a mixed caloric load is eaten affects the thermogenic response and may be an important determinant of energy balance after a meal (1).
When discussing the relationship between TEF and fullness sensation, the objective of another study was to evaluate energy expenditure after three isoenergetic meals of different nutrient composition and to establish the relationship between TEF and satiety sensations related to consumption (2). Ten subjects received, in a randomized order, three meals of 557±9 kcal. About 68% of energy from protein in the high protein meal (HP), 69% from carbohydrate in the high carbohydrate meal (HC) and 70% from fat in the high fat meal (HF). The HP meal was the most thermogenic and it determined the highest sensation of fullness. There were no differences in the sensations and thermic effect between fat and carbohydrate meals. A significant relationship linked TEF to fullness sensation (2). Their conclusions suggest that TEF contributes to the satiating power of foods.
Another study's objective was to observe the effect of diet composition on diet-induced thermogenesis (DIT) over 24 h in a respiration chamber (3). The subjects were to consume either a high protein and carbohydrate (HP/C) (60:10:30; percentage energy) or high fat (HF) (30:60:10 respectively) diet, both isoenergetic and isovolumetric (3). Subjects spent two 36 h periods each in a respiration chamber consuming both test diets in random order. Components of 24 h energy expenditure: sleeping metabolic rate, DIT and activity induced energy expenditure were measured (3). DIT was higher in all subjects while on the HP/C diet suggesting a high protein and carbohydrate diet induces a greater thermic response in healthy individuals when compared to a high fat diet (3).
Although these are all formally conducted research experiments, their findings should still be 'taken with a grain of salt'. I think this is some valuable information, especially when trying to optimize TEF, but keep in mind that that is still a very small percentage of your TDEE. So, if your goal is to alter body composition and lose fat I'd focus more on the total caloric deficit and non-exercise activity thermogenesis (NEAT).
1. M M Tai, P Castillo, F X Pi-Sunyer, Meal size and frequency: effect on the thermic effect of food, The American Journal of Clinical Nutrition, Volume 54, Issue 5, November 1991, Pages 783–787, https://doi.org/10.1093/ajcn/54.5.783
2. Crovetti, R., Porrini, M., Santangelo, A. et al. The influence of thermic effect of food on satiety. Eur J Clin Nutr 52, 482–488 (1998). https://doi.org/10.1038/sj.ejcn.1600578
3. Westerterp, K., Wilson, S. & Rolland, V. Diet induced thermogenesis measured over 24h in a respiration chamber: effect of diet composition. Int J Obes 23, 287–292 (1999). https://doi.org/10.1038/sj.ijo.0800810