Digesting food burns about 10% of your daily calories
High confidence
Every time you eat, your body spends energy breaking the food down. This is the thermic effect of food, and it burns about 10 percent of the calories you use each day. Protein costs the most to process, more than carbs or fat.
Why it works
Your body burns energy to digest food, absorb it, and put it to use. Protein costs the most. The body has to break its amino acids down, stripping off nitrogen (deamination) and packaging that nitrogen into urea to clear it (ureagenesis). It can also build fresh glucose from what's left (gluconeogenesis). Each step takes work.
The evidence
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This review reports that the thermic effect of food (the energy your body burns digesting and processing a meal) accounts for about 10% of total calorie intake in healthy adults eating a normal mixed diet. Protein has the highest thermic effect at 20% to 30% of the calories eaten, compared with 5% to 10% for carbohydrate and 0% to 3% for fat. The authors also conclude that TEF rises with larger meals and is higher on low-fat, plant-based diets, likely because those diets tend to be higher in carbohydrate and lower in fat.
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In 7 healthy young men studied in a metabolic chamber for 33 hours with and without breakfast, the authors tested a new way to calculate the thermic effect of food that removes the noise from spontaneous movement. Their method gave a morning TEF of 4.1% (plus or minus 2.5%) of meal energy, with all values positive, while some older methods produced negative or highly variable results. The new method matched the gold-standard measure closely (mean difference of about 1.3%, no significant bias) and tracked physical activity far better (R-squared 0.45 versus 0.17 for a conventional method).
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Ten healthy, normal-weight women each ate three meals of about 557 kcal that were matched for calories but differed in makeup: high protein (68% of energy from protein), high carbohydrate (69%), or high fat (70%). The high-protein meal more than doubled the thermic effect of food compared with the high-fat and high-carbohydrate meals, and it also produced the strongest feeling of fullness. The authors conclude that the thermic effect of food contributes to how filling a meal feels.
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This methods paper analyzed 131 thermic-effect-of-food tests, each run for 6 hours, across subjects eating meals of different sizes and compositions. It found that a 6-hour test captured the response far more completely than shorter tests: only 60% of the total was measured by 3 hours, 78% by 4 hours, and 91% by 5 hours, meaning short tests underestimate TEF. The authors fitted a three-parameter curve to the data, which reduced measurement noise and gave a more reliable estimate of the full thermic response.
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Sixteen non-obese women each ate four test meals that varied in makeup (high-carbohydrate-low-fat vs low-carbohydrate-high-fat) and in size (600 kcal vs 1,200 kcal). Meal composition made no significant difference to the thermic effect of food, but meal size did: the 600 kcal meals produced about 54 kcal of TEF (roughly 9% of the meal) and the 1,200 kcal meals about 81 to 85 kcal (roughly 7%). The authors note metabolic rate had not fully returned to baseline by 5 hours, so these figures likely underestimate the total thermic effect.
Why we call confidence high
These ranges show up consistently across many reviews and metabolic chamber studies, spanning decades. The ranking of protein over carbohydrate over fat is one of the most replicated findings in this corner of nutrition science.
Where it applies
Healthy adults
Last reviewed May 25, 2026. See how we score.