After you eat, your body uses up some of the calories (or energy) in the food to digest, absorb and store nutrients your cells need to function.
The thermic effect of food (TEF) is the increase in metabolic rate — the rate at which your body burns calories or energy — that occurs after ingestion, Valerie Agyeman, RD at Flourish Heights, tells LIVESTRONG.com.
"The TEF accounts for 10 to 15 percent of the total energy expenditure and is influenced by the timing of meals, caloric content and macronutrient composition," Mariana Dineen, RD, CDN, says.
"A number of studies have shown that the thermic effect of food is higher in the morning and reduced in the evening. A proposed mechanism for this may be the effect of our circadian rhythms on metabolism," she says.
Interestingly, not all foods are created equal — and some foods have a higher thermic effect than others. FYI, this is one of the reasons why a varied pattern of eating is supportive of overall metabolic health.
The TEF of Carbs vs. Fat vs. Protein
When it comes to the three macros, protein, carbs and fat all seem to have varying TEF.
"Research shows that protein has the highest thermic effect," Marisa Moore, RDN, tells us. "Protein requires between 15 to 30 percent more energy to digest, followed by carbohydrates at 5 to 10 percent and fats which are significantly lower at 0 to 3 percent."
"For every 100 calories of protein consumed, about 20 to 30 calories are spent during digestion and absorption," explains Cordiails Msora-Kasago, RDN and media spokesperson for the Academy of Nutrition and Dietetics.
"Carbohydrate-rich foods such as whole grains, sweet potatoes and fruits have a 5 to 10 percent effect while fats such as oils are the easiest for the body to absorb with a rate of 0 to 3 percent."
She credits this phenomenon to protein's ability to keep blood sugar levels stable, thus avoiding the sharp, temporary ups and downs in blood glucose that are associated with hunger pangs.
The key, of course, is picking the best proteins to add to your nutrition plan. Great choices in this category include proteins in their whole and minimally processed form with limited added sugars and synthetic fats, such as:
- Lean meats
- Unsweetened fermented dairy
These options require your body to use more energy to digest them, increasing their thermic effect, Vanessa Rissetto, RD, CDN, says.
In fact, researchers speculate that the increased oxygen demand needed to metabolize protein foods might cause an increase in satiety, according to a 2014 article in the Journal of Nutrition & Metabolism.
Replacing refined grains with whole grains may have beneficial effects on energy regulation and metabolism.
In a March 2017 study in The American Journal of Clinical Nutrition, participants were asked to substitute whole grains for refined grains throughout a 6-week period.
By the end of the study, people who ate around 35 to 45 grams of fiber noticed an increase in their metabolism.
What About Other Supposed Metabolism-Boosting Foods?
While some spices and caffeine seem to prolong and enhance TEF, other supposed metabolism-boosting foods lack the research needed to confirm they indeed increase TEF.
A July 2013 study in PLOS One notes that capsaicin — which is found in chili peppers and paprika — can bolster your metabolic rate and promotes fat burning.
2. Green Tea
The mechanism of action behind the enhanced thermogenesis in tea is catechins and caffeine, the two main components of green tea.
"Although green tea is one of the healthiest beverages, its long-term effect on increasing energy expenditure is not currently proven," Dineen says, adding something we do know: "Caffeine does give a temporary lift to the metabolic process."
"Ginger has been hypothesized as another food that increases TEF," Dineen says.
"And although it can be a helpful preventive treatment for nausea, human studies about ginger's effects of TEF are inconclusive and have yielded contrasting results."
4. Apple Cider Vinegar
"It is rich in polyphenols, acetic acid and makes great dressings but unfortunately, the lack of human studies makes it impossible to draw conclusions about the potential effects it has on energy and metabolism," Dineen says.
- Journal of Nutrition & Metabolism: "A high-protein diet for reducing body fat: mechanisms and possible caveats"
- PLOS One: "Acute Effects of Capsaicin on Energy Expenditure and Fat Oxidation in Negative Energy Balance"
- The American Journal of Clinical Nutrition: "Substituting whole grain for refined grain: what is needed to strengthen the scientific evidence for health outcomes?"
- World Fitness Network: Burn Fat With the Thermic Effect of Food