The main determinant of DIT is the energy content of the food, followed by the protein fraction of the food. The thermic effect of alcohol is similar to the thermic effect of protein.
Diet induced thermogenesis is related to the stimulation of energy-requiring processes during the post-prandial period. The intestinal absorption of nutrients, the initial steps of their metabolism and the storage of the absorbed but not immediately oxidized nutrients . As such, the amount of food ingested quantified as the energy content of the food is a determinant of DIT. The most common way to express DIT is derived from this phenomenon, the difference between energy expenditure after food consumption and basal energy expenditure, divided by the rate of nutrient energy administration .
Theoretically, based on the amount of ATP required for the initial steps of metabolism and storage, the DIT is different for each nutrient. Reported DIT values for separate nutrients are 0 to 3% for fat, 5 to 10% for carbohydrate, 20 to 30% for protein , and 10 to 30% for alcohol . In healthy subjects with a mixed diet, DIT represents about 10% of the total amount of energy ingested over 24 h. When a subject is in energy balance, where intake equals expenditure, DIT is 10% of daily energy expenditure.
Of the studies presented in table 1, most reported a DIT value below 10% of the energy content of the food ingested. The studies reporting a DIT value below 10% measured DIT as the increase in energy expenditure above basal fasting level over an interval of 4 to 5.5 h after the meal. The studies with a higher value included a study with pure alcohol consumption and the studies where DIT was measured over 24 h in a respiration chamber. In the respiration chamber studies, DIT values were calculated as the increase in energy expenditure above sleeping metabolic rate while the other studies reported DIT as the increase in energy expenditure above basal metabolic rate. Basal metabolic rate is about 5% higher than sleeping metabolic rate . After correction of the DIT values based on sleeping metabolic rate to the increase in energy expenditure above basal metabolic rate, the chamber values are close to the values of 10% of daily energy intake.
The higher DIT value of alcohol and protein compared with carbohydrate and fat has implications for the effect of these nutrients on energy balance. However, the main effect on energy balance does not seem to be primarily linked to the lower bioavailability of alcohol-and protein energy than that of fat and carbohydrate. Alcohol energy is largely additive to the normal diet but does not seem to affect energy balance positively . Protein plays a key role in food intake regulation through satiety related to DIT .
Alcohol forms a significant component of many diets and it supplements rather than displaces daily energy intake. Alcohol consumption as an aperitif has even been shown to result in a higher subsequent intake with no intake compensation afterwards . Yet, alcohol intake does not systematically increase body weight. In a recent study, it was shown that subjects with higher alcohol consumption are habitually more active . This may be one explanation for the lack of increasing body weight through additional energy intake from alcohol.
The main effect of protein on energy balance is thought to be DIT related satiety. Satiety scores were higher during meals with a high-protein/high-carbohydrate diet, as well as over 24 h, than with a high-fat diet . The observed DIT related satiety might be ascribed to the high protein rather than the high carbohydrate content of the diet. Postprandial thermogenesis was increased 100% on a high-protein/low-fat diet versus a high-carbohydrate/low-fat diet in healthy subjects . The DIT increases body temperature, which may be translated into satiety feelings. High-protein diets are favored for weight maintenance, also after weight loss, by favoring maintenance or regain of fat-free mass, by reducing the energy efficiency through a higher thermogenesis, and by reducing intake through an increased satiety .
In conclusion, the main determinants of diet-induced thermogenesis are the energy content and the protein-and alcohol fraction of the diet. Protein plays a key role in body weight regulation through satiety related to diet-induced thermogenesis.