Thermic Effect of Food: How Many Calories Does Digestion Burn

Protein digestion is by far the most energy-intensive process, with 20-30% of protein calories going to digestion. If you eat 100 grams of chicken breast, which contains about 165 calories of protein, 33-50 of those calories are spent on the digestive process. Carbohydrate digestion has moderate energy requirements, using about 5-10%. Fat digestion is the most efficient, with almost all calories being absorbed and utilized, only 0-3% is lost. That's why a high protein diet burns more calories long-term than a low protein one, even with identical calorie intake.

Yes, high protein intake supports fat loss in multiple ways through the thermic effect of food. If 30% of your daily calories come from protein instead of 10%, this alone can burn an extra 50-100 calories per day. Protein provides longer satiety and stabilizes blood sugar levels, making you less likely to overeat. The digestive process is slower with protein, keeping your metabolism elevated for several hours. In a calorie deficit, high protein intake also protects muscle mass, which is important for maintaining metabolism.

Yes, after every meal your metabolic rate increases, called postprandial thermogenesis. Your body's energy expenditure begins to rise 30-60 minutes after eating and stays elevated for 3-6 hours. After a protein-rich meal, your metabolism can increase by 20-30% for a short time. This doesn't mean eating more frequently burns more calories, because total daily TEF depends on calories and macros consumed, not meal frequency. The point is that your body truly works to process food, and this costs energy.

Research shows that meal frequency doesn't significantly affect the total daily calories used by digestion. If you eat 2000 calories daily, the cumulative TEF will be the same whether you have 3 or 6 meals, assuming you consume the same macros. What matters is total daily intake and macro distribution, not meal frequency. Some people feel better with frequent smaller meals, others with fewer large meals, both methods can work. The key is finding a pattern you can maintain long-term that provides good satiety.

The thermic effect of food accounts for about 10% of your total daily calorie burn with an average diet. If you eat 2000 calories daily, roughly 200 calories go to digestion. With a high protein diet (40% protein), this can increase to 300-350 calories, while low protein (10% protein) may only be around 150. This represents a 100-150 calorie difference daily, which equals about half a kilogram of fat loss per month. While not a huge number, it adds up long-term, and combined with other strategies can have significant impact.