Do foods that boost metabolism work? The measured numbers

Key takeaways

• No food moves metabolism by much. Measured effects run from nothing for room temperature water to about 100 calories a day for green tea extract or caffeine supplements in lab studies.⁵¹
• In a meta-analysis of respiration chamber studies, green tea catechins with caffeine raised 24 hour burn by 4.7 percent and caffeine alone by 4.8 percent, about the same.¹
• Capsaicin from chili had no overall effect on burn in a 2012 meta-analysis, with a rise only at high doses. The authors put palatable doses at about 10 calories a day.³
• Protein costs the most to digest, 20 to 30 percent of its calories, against 5 to 10 percent for carbs and 0 to 3 percent for fat.⁶
• The 30 percent boost from drinking water, reported in 2003, didn't hold up. In a 2006 study, room temperature water didn't raise burn at all.⁴⁵

Do foods that boost metabolism work?

Only a little. Green tea, caffeine, chili and cold water each raised calorie burn by small amounts in lab studies, from nothing to about 100 calories a day, and the larger numbers came from supplement doses, not cups of tea or bowls of chili.¹³⁵

The food effect with the clearest size is the cost of digesting protein, 20 to 30 percent of the protein's own calories. That's built into the food, not an extra boost on top of it.⁶

How much does each food boost metabolism?

Read the rows side by side. Kilojoule figures are converted to calories by dividing by 4.184.

Does green tea boost metabolism?

A little, and caffeine alone did about as well. In a 2011 meta-analysis of respiration chamber studies, catechin and caffeine mixtures raised 24 hour burn by 428 kilojoules, about 102 calories, or 4.7 percent. Caffeine alone raised it by 429 kilojoules, or 4.8 percent. Fat burning, measured as fat oxidation, rose only with the catechin and caffeine mixtures, by 12.2 grams over 24 hours.¹

Those were supplement doses. The same analysis found burn rose with dose, by about 0.44 kilojoules per milligram of caffeine. A cup of brewed green tea has about 29 milligrams of caffeine in USDA's data.¹⁷

On body weight, a 2009 meta-analysis of 11 studies found catechins lowered weight by 1.31 kilograms on average compared with control. The effect looked smaller in people who already took in more than 300 milligrams of caffeine a day, though that difference wasn't statistically clear.²

Do spicy foods boost metabolism?

Barely. A 2012 meta-analysis found capsaicin, the hot compound in chili peppers, had no overall effect on energy burn, with an increase only at high doses. Capsiate, a non-spicy relative found in some sweet peppers, did raise burn.³

The authors put the size in plain terms. A 10 calorie a day shift, which they predicted for capsaicin at doses people find palatable, would add up to about half a kilogram of weight change over 6.5 years in the weight model they used.³

Does drinking water boost metabolism?

Probably not by much. A 2003 study of 14 people reported that drinking 500 milliliters of water raised metabolic rate by 30 percent, a total of about 100 kilojoules, or about 24 calories. About 40 percent of that came from warming the water to body temperature.⁴

A 2006 study tried it again with about 518 milliliters. Room temperature water didn't raise burn at all. Water cooled to 3 degrees Celsius raised it by 4.5 percent over 60 minutes, which the authors called well below the energy cost of warming that water to body temperature.⁵

Does protein boost metabolism?

In one sense, yes. Protein costs the most to digest. Digesting and storing food uses 20 to 30 percent of the calories in protein, 5 to 10 percent for carbs, 0 to 3 percent for fat and 10 to 30 percent for alcohol. On a mixed diet, that digestion cost is 5 to 15 percent of daily burn.⁶

So 100 calories of protein uses about 20 to 30 of those calories in digestion, and 100 calories of fat uses 0 to 3. Protein's effect on fullness is tied to this cost too.⁶

What actually changes how many calories you burn?

Digestion is one of three parts of daily burn, along with resting burn and the energy cost of activity. On a mixed diet it's 5 to 15 percent of the total, so food choices act on that slice.⁶

The TDEE guide covers resting burn and activity, and the starvation mode guide covers how burn adapts as weight changes.

How to track it

• Leave metabolism boosting foods out of your calorie math, and log the foods and drinks themselves.
• Log tea and coffee with any milk, sugar or syrup you add.
• To learn your real burn, compare a few weeks of logged intake with your weight trend, as the TDEE guide shows.
• TrueCal with Pro tracks caffeine against a daily budget, next to calories, protein, carbs and fat.

Common myths

• Myth, green tea melts fat. Its measured effect on 24 hour burn was 4.7 percent at supplement doses, close to caffeine alone.¹
• Myth, 2 liters of water a day burns about 100 calories. That estimate came from a 2003 study of 14 people, and in a 2006 study room temperature water didn't raise burn at all.⁴⁵
• Myth, spicy food speeds up your metabolism. Capsaicin had no overall effect in the 2012 meta-analysis, only a rise at high doses.³

A note on medical advice

This article is for general information and isn't medical or supplement advice. Talk with your clinician about your own situation.

Worked example

Here's rough arithmetic with the caffeine dose slope from the 2011 meta-analysis, about 0.44 kilojoules per milligram. A cup of brewed green tea has about 29 milligrams of caffeine, which works out to about 13 kilojoules, or about 3 calories. A cup of brewed coffee has about 95 milligrams, about 42 kilojoules, or about 10 calories. The slope came from supplement studies, so treat these as estimates, not measured results for a cup.¹⁷⁸

A closer look

The 30 percent metabolism boost from drinking water came from a 2003 study of 14 people. When a 2006 study repeated the test with about 518 milliliters, room temperature water didn't raise calorie burn at all, and water cooled to 3 degrees Celsius raised it 4.5 percent over 60 minutes.⁴⁵

Questions and answers

Related guides

• How to track calories
• Is starvation mode real?
• What is TDEE?
• What is CICO?
• High protein, low calorie foods
• The slow metabolism myth
• How much caffeine is in coffee?

Sources

1. Obesity Reviews. Hursel. 2011.
2. International Journal of Obesity. Hursel. 2009.
3. Chemical Senses. Ludy. 2012.
4. Journal of Clinical Endocrinology and Metabolism. Boschmann. 2003.
5. Journal of Clinical Endocrinology and Metabolism. Brown. 2006.
6. Nutrition and Metabolism. Westerterp. 2004.
7. Beverages, tea, green, brewed, regular. USDA FoodData Central. 2019.
8. Beverages, coffee, brewed, prepared with tap water. USDA FoodData Central. 2019.