The thermic effect of food (TEF) is the amount of energy required to digest and process the food you eat. Basically, every bite of food “costs” a certain number of calories to break down.
Knowledge of this fact has also given rise to many dippy theories about how to lose weight.
For instance, some people claim there are “negative calorie foods” that actually cost more energy to digest than they provide.
Others claim that by “nibbling” small meals every few hours, you can keep fat loss humming along throughout the day.
And others claim that gorging on protein and other foods with a high thermic effect can produce similar benefits.
Here’s the home truth:
Although you can increase your daily TEF by eating more protein and whole foods, increasing your meal frequency or size will not (eating more often won’t “boost” your metabolism). What’s more, you still need to control your calorie intake, regardless of the TEF of your meals.
Keep reading to learn how the thermic effect of food works, how to boost the thermic effect of food, and to get an extensive list of high-thermic foods.
The thermic effect of food (TEF) is the amount of energy required to digest and process the food you eat, and the main determinants of TEF are the macronutrient composition of the meal, how processed the foods are, and the size of your meal.
Generally, TEF is measured as a percentage of the calories of a food that are required to digest that food. In other words, if a portion of a particular food contains 100 calories, and the body burns 20 calories to digest it, that food has a TEF of 20% (20 / 100 = 20%).
The single biggest determinant of the thermic effect of food is the macronutrient composition of your meals. Here’s how it breaks down:
- Protein tops the list with a TEF of around 20-to-35%.
- Carbs are next with a TEF of around 5-to-10%.
- And fat is last a TEF of about 0-to-3%.
Alcohol has a high TEF of around 10-to-15%, which leads some people to believe that drinking alcohol might actually be good for fat loss. The problem with this line of thinking, though, is that although alcohol has a high TEF, it can also reduce fat burning in other ways (especially when you’re in a calorie surplus).
After macronutrient composition, the second major determinant of TEF is the level of processing a food has undergone—foods that are more processed have a lower TEF than foods that are less processed.
For example, a study conducted by scientists at Pomona College found a processed-food meal of white bread and American cheese increased TEF about 10%, whereas a whole-food meal of multi-grain bread and cheddar cheese increased TEF about 20%. The difference would likely be even higher if the subjects ate a meal of high-fiber vegetables and lean protein (which is even less processed than multi-grain bread and cheddar cheese).
Finally, how much food you eat in one sitting also affects your post-meal TEF, with larger meals causing a bigger increase than smaller ones.
And how does all of this affect your metabolism? I’ll explain that in a moment, but the long story short is that you can slightly boost your metabolic rate by consuming more high-thermic foods. That said, you still need to control your calorie intake to lose weight—just eating these foods won’t be enough.
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While no food can “burn fat,” some high-thermic foods can make it slightly easier to lose weight and keep it off.
Remember that the foods with high thermic effect tend to be minimally processed foods, and this is true of proteins, carbs, and fats, so you want to prioritize these in your diet to maximize TEF. For instance, although all high-protein foods have a high TEF, chicken breast would be better than whey protein in this regard because it’s less processed.
- Bulgar wheat
- Kidney bean
- Chicken or turkey
- Pork tenderloin
- Mutton (fat removed)
- Cottage cheese or Greek yogurt (low-fat)
- Pumpkin seed
- Flax seed
- Chia seed
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When you eat food, energy expenditure rises, which is good for fat loss.
What’s bad for fat loss, though, is that after eating a meal . . .
And no matter how high the thermic effect of the food you eat, the calories in that food will always reduce fat burning. In other words, eating food doesn’t burn fat. Energy expenditure does.
Some foods result in less fat storage than others, but rest assured that an energy surplus results in some degree of fat gain regardless of the composition of your diet.
Your body only starts to burn body fat when your last meal is fully digested and absorbed, and thus when calories are becoming scarce. The relationship between the amount of energy you expend (burn) and consume (eat) is referred to as energy balance, and it works like this:
- If you eat more energy than you burn, you’re in a state of positive energy balance, and you will gain fat.
- If you eat less energy than you burn, you’re in a state of negative energy balance, and you will lose fat.
- If you eat about the same amount of energy that you burn, you’re in a state of neutral energy balance, and will maintain your weight.
This is true regardless of the types of foods you eat or how high or low their thermic effect is.
Recall that the thermic effect of food contributes to overall energy expenditure, which means it contributes to weight loss by increasing the amount of energy your body burns. That’s the good news.
The bad news is that the magnitude of these effects is far too small to really move the needle.
You can gain weight on a diet rich in high-TEF foods because you simply eat too much of them, and you can lose weight on a diet rich in low-TEF foods because you simply know how many calories to eat and regulate your intake of them.
This is why the entire idea of “fat-burning foods” is a myth.
Instead, eating foods with a higher thermic effect can help make your diet slightly more effective, but it will never be enough to help you lose a substantial amount of fat on its own.
If you’d like specific advice about how many calories, how much of each macronutrient, and which foods you should eat to reach your weigh-loss goals, take the Legion Diet Quiz.
Or, if you’d like to learn more about how to set up an effective fat loss diet that helps you lose fat each and every week, eating foods you like, check out our custom meal planning service.
+ Scientific References
- Kersten, S. (2001). Mechanisms of nutritional and hormonal regulation of lipogenesis. EMBO Reports, 2(4), 282. https://doi.org/10.1093/EMBO-REPORTS/KVE071
- LC, G., RC, B., M, S., AS, P., & RA, D. (1991). Role of free fatty acids and insulin in determining free fatty acid and lipid oxidation in man. The Journal of Clinical Investigation, 87(1), 83–89. https://doi.org/10.1172/JCI115005
- Westerterp, K. R. (2004). Diet induced thermogenesis. Nutrition & Metabolism 2004 1:1, 1(1), 1–5. https://doi.org/10.1186/1743-7075-1-5
- Barr, S. B., & Wright, J. C. (2010). Postprandial energy expenditure in whole-food and processed-food meals: implications for daily energy expenditure. Food & Nutrition Research, 54. https://doi.org/10.3402/FNR.V54I0.5144
- PM, S., E, J., & Y, S. (1994). Effect of ethanol on energy expenditure. The American Journal of Physiology, 266(4 Pt 2). https://doi.org/10.1152/AJPREGU.1994.266.4.R1204
- Westerterp, K. R. (2004). Diet induced thermogenesis. Nutrition & Metabolism, 1, 5. https://doi.org/10.1186/1743-7075-1-5
- L, T. (1996). Thermic effect of food and sympathetic nervous system activity in humans. Reproduction, Nutrition, Development, 36(4), 391–397. https://doi.org/10.1051/RND:19960405