Nutritional science has long discussed and researched whether there is a difference in calorie utilization depending on the time of day. For a long time, the question remained open as to whether variation in the time of day plays a role in diet-induced thermogenesis (DIT). In February 2020, this question was answered in a new randomized controlled study. Here, identical calorie consumption led to a 2.5-fold increase in DIT in the morning compared to the evening. Blood glucose and insulin concentrations after food intake were also significantly reduced after breakfast. These results were independent of the amount of calories consumed, which means that even when a reduction diet is pursued, the amount of calories burned in the morning is greater. It follows that a substantial breakfast should be preferred to a large dinner in order to avoid overweight, obesity and high blood glucose peaks. The study also screened hunger sensations and cravings for sweets, with a low-energy breakfast leading to stronger hunger, particularly for sweets (Richter, Herzog, Janka, et al., 2020).
What Actually Determines the Body’s Energy Expenditure?
The total energy expenditure of humans depends on three variables:Basal metabolic rate, activity-related energy expenditure and diet-induced thermogenesis (DIT).
- Basal Metabolic Rate: This describes the amount of energy that the body uses in maintaining vital functions (e.g., heartbeat and respiration) and depends on age, gender and body weight and composition. The higher the proportion of muscle mass, the higher the basal metabolic rate.
- Activity-Related Energy Expenditure: This expenditure reflects the amount of energy for all other physical demands. This naturally includes muscle work (movement and exercise), but activity-related energy expenditure is also increased during growth or pregnancy and lactation. Lifestyle therefore plays a major role in activity-related energy expenditure and is thus an important lever for influencing body weight.
- Diet-Induced Thermogenesis: This does not refer to the body’s fat burning, but to the thermal effect of food. Diet-induced thermogenesis is defined as the increase in body temperature and heat release to the environment above the basal metabolic rate. It accounts for approximately 6-10% of energy expenditure (Biesalski, Grimm, Nowitzki-Grimm, 2020). In the study by researcher Juliane Richter, it has now been shown that breakfast has a more efficient energetic value for our body with regard to DIT than dinner (Richter, Herzog, Janka, et al., 2020).
References: Biesalski HK, Grimm P, Nowitzki-Grimm S. Energiehaushalt. In: 8., vollständig überarbeitete Auflage. Georg Thieme Verlag; 2020. Richter J, Herzog N, Janka S, et al. Twice as High Diet-Induced Thermogenesis After Breakfast vs Dinner On High-Calorie as Well as Low-Calorie Meals. J Clin Endocrinol Metab. 2020;105(3):211-221.
