Definition
The thermic effect of food (TEF) is the energy your body spends to digest, absorb, transport, and metabolize the food you eat. It accounts for around 10% of your total daily energy expenditure. In other words, part of the calories you eat are used right away to process that very same food.
Detailed explanation
How does the thermic effect of food work?
When you eat, your body doesn't just stash the energy away. It first has to break down the food into usable nutrients, transport them through the bloodstream to your cells, and then convert them into energy or structural building blocks. Each of these steps burns energy and produces heat (hence the term "thermic").
That's why you can feel warm after a big meal: your body is literally burning calories to process what you just ate.
The thermic effect varies by macronutrient
Not all foods take the same effort to digest. The thermic effect varies a lot by macronutrient:
- Protein: 20 to 35% of the calories are used for digestion. The highest thermic effect by far. For every 100 kcal of protein you eat, 20 to 35 kcal are burned just digesting it.
- Carbs: 5 to 15% of the calories. Complex carbs (whole grains, legumes) have a higher thermic effect than simple sugars.
- Fat: 0 to 5% of the calories. Fats are the easiest to digest and store, which is part of why excess fat intake encourages fat gain.
Real impact on energy expenditure
For someone eating 2,000 kcal per day, the thermic effect of food accounts for around 200 kcal of daily expenditure. That's not nothing. By raising the protein share of your diet (going from 15% to 30% of calories), you can boost this expenditure by 50 to 80 kcal per day. Over a month, that's the energy equivalent of 200 to 250 grams of fat.
This is one of the reasons high-protein diets are so effective for fat loss: protein is not only more filling, it also costs more energy to digest.
In practice
To make the most of the thermic effect of food in your weight management:
- Boost your protein intake at every meal (lean meat, fish, eggs, legumes).
- Lean on whole foods rather than ultra-processed products.
- Spread your meals across the day instead of cramming all your calories into one sitting.
- Use the calorie calculator to balance your intake.
TEF is still a minor part of total expenditure. Basal metabolism and physical activity will always have a bigger impact, but optimizing TEF through protein is an easy win.
Useful links
Want to dial in your nutrition easily? Try Kalo on WhatsApp — your nutrition coach analyzes your meals in seconds.