The thermic effect of foods: How many calories does our body burn through digestion? Is it the same digesting fats as it is protein?…
Whether our goal is to gain muscle mass, lose fat tissue, maintain our weight, or simply look after our health, we should pay attention to our energy balance
What is the Energy Balance?
The energy balance is the relationship between the energy intake (what you eat) and the energy expenditure (what’s used up), which results in three possible conditions:
- Calorie surplus (when we intake more energy than we expend),
- Calorie deficit (when we expend more energy than we consume) or,
- Isocaloric consumption (when our calorie ingestion and expenditure is similar enough not to cause any fluctuations in body weight).
Quantifying Energy Expenditure
From the old paradigms of clinical nutrition to the present day, 3 fundamentals have been maintained as the pillars constituting energy expenditure:
- The basal metabolic rate (BMR): which is the energy expenditure our body produces to maintain our vital functions.
- The energy expenditure associated with physical activity: made up of physical exercise and daily NEAT.
- Thermogenesis: the effect of certain substances on energy expenditure, dependent or independent of their association with physical activity. Examples of this are stimulants such as caffeine or nicotine, the cold or particular foods.
However, quantifying energy expenditure is a little more complex
The Thermic Effect of Food or TEF
In this article we’ll focus on the effect of food consumption on fluctuations in daily energy expenditure. In addition to being a source of energy intake, food consumption, to a certain extent, also has an associated energy expenditure.
The TEF is the percentage of energy consumed which is required for the processes of digestion and assimilation of nutrients
That’s why, depending on the quantity and distribution of nutrients in each intake, our energy expenditure varies
Nutrients and TEF
The TEF is not dependent on the food source consumed, i.e. our body will not vary, or at least not significantly, the energy expenditure if our source of carbohydrates is bread or rice (at equal amounts of nutrients).
However, the thermogenesis associated with food consumption is different if we consume a portion of carbohydrates, fats or proteins
Different nutrients have different levels of associated energy expenditure required for their assimilation
Thermic Effect depending on macronutrient
Proteins have an energy expenditure associated with their consumption of between 20 and 30% of the total caloric intake, carbohydrates between 5 and 10%, and fats between 0 and 3% (Ravn et al, 2013).
This is due to the energy efficiency of the nutrient, i.e. how easy it is for our body to metabolise the nutrient
We can conclude, then, that proteins are a very inefficient energy nutrient; nevertheless, if our objective is to lose weight, it’s possible to take advantage of this
Is 1 kilocalorie a kilocalorie?
No, an intake of 1000kcal of protein generates an energy expenditure of between 200 and 300kcal, in the metabolisation processes, while the same intake of fat generates a thermal effect of between 0 and 30kcal.
That’s to say, they are not going to fatten us up the same
TEF and physical activity
It’s interesting to note that food-induced thermogenesis is strongly affected by subsequent exercise practice (Binns et al. 2015).
10 active women performed 30 minutes of physical exercise at 60% of their Vo2Max. after a high protein intake (45% kcal intake) vs low protein intake (15% kcal intake) vs fasting;
Energy consumption was significantly higher during physical exercise after a high protein intake vs fasting, but not after a low protein intake vs fasting.
Figure I. Variations in metabolic expenditure under different conditions RMRH: After high protein intake; RMRL: After low protein intake; RMRF: Fasting
- Energy is required to metabolise and assimilate the nutrients from food.
- Protein is the nutrient that produces the greatest thermal effect.
- Physical exercise immediately following food consumption produces an increase in the extent of the thermal effect of food, although this appears to be significant only if the previous intake is rich in protein.
- The TEF must be quantified to make a correct estimation of the daily energy expenditure and to be able to control all the factors that influence our body modifications.
- Binns, A., Gray, M., & Di Brezzo, R. (2015). Thermic effect of food, exercise, and total energy expenditure in active females. Journal of Science and Medicine in Sport, 18(2), 204–208. https://doi.org/10.1016/j.jsams.2014.01.008
- Ravn, A.-M., Gregersen, N. T., Christensen, R., Rasmussen, L. G., Hels, O., Belza, A., … Astrup, A. (2013). Thermic effect of a meal and appetite in adults: an individual participant data meta-analysis of meal-test trials. Food & Nutrition Research. https://doi.org/10.3402/fnr.v57i0.19676
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