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How Caffeine Affects Your Metabolism 

Posted on February 28, 2024 by Henry Ford Health Staff
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Coffee, tea and energy drinks are go-to caffeine sources for many Americans wanting to fight morning fatigue, improve focus or fuel a mid-afternoon pick-me-up. Caffeine is a naturally occurring stimulant in foods such as chocolate and matcha tea. It’s added to other products, including soda, supplements and energy drinks. 

Recent research suggests that caffeine may do more than perk us up—it may function as a fat burner, says Allegra Picano, RDN, a dietitian at Henry Ford Health. “There have been quite a few studies that suggest higher blood concentrations of caffeine may be associated with a lower body mass index (BMI) and lower body fat mass.” And since studies have shown weight loss improves insulin sensitivity and lowers diabetes risk, caffeine’s positive effects may be even more far-reaching.

Fat Loss And Caffeine

There’s not yet enough evidence to say that caffeine is a tried-and-true method for losing fat, but it may help promote fat loss. 

Research has shown caffeine acts on the nervous system and stimulates epinephrine, a hormone involved in fat breakdown. “One of the studies stated that a person who consumed twice as much caffeine as another had 22% more reduction in weight, 17% more reduction in BMI and 28% more reduction in body fat,” says Picano. Another study found that overweight people who drank four cups of coffee per day lost about 3.7% of their body fat versus people who drank the same amount of a placebo. 

Metabolism And Caffeine

Other studies suggest that caffeine increases resting metabolic rate (RMR), the rate at which your body breaks down food while your body is at rest. Your RMR is one way to measure your metabolism, including how many calories you burn when you’re not at rest (energy expenditure). 

One study of caffeinated tea’s effects on energy expenditure found that active people who drank caffeinated tea for two weeks burned 96 more calories per day than those who drank a placebo. “This extra calorie burn could help with weight loss and body fat reduction,” says Picano. 

She also notes that certain groups may be more sensitive to caffeine’s effects on metabolism than others. “People with a lower BMI seem to have larger increases in metabolism from caffeine than those with a higher BMI or who are considered obese.”

Recommended Caffeine Intake

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So what’s the bottom line on using caffeine for weight loss? The FDA says between 200 and 400 milligrams per day (two to four cups of coffee) is safe and may have some benefits. Picano cautions, though, that studying caffeine’s effects on body fat can be challenging because caffeinated foods and beverages like coffee contain compounds such as antioxidants that might contribute to fat loss.

“We have a limited number of studies and not enough information to recommend people to drink a certain amount of caffeine per day to lose weight or burn more body fat," she says. "We also don’t know the long-term effects.” And she cautions people to be wary of the side effects of too much caffeine—nausea, increased heart rate and nervousness or jitters.

Your best bet? Use caffeine moderately as part of a healthy lifestyle and choose caffeine sources with other health benefits. “Coffee is the most popular caffeinated beverage, but tea also has benefits such as polyphenols and other antioxidants that can help reduce inflammation in the body," says Picano. "And focus on getting regular exercise and eating a well-balanced diet with fruits, vegetables, lean protein, whole grains and healthy fats. That would benefit you more than taking a caffeine supplement or relying on other caffeine sources.”


Reviewed by Allegra Picano, RDN, a registered dietitian at Henry Ford Health.

Categories : EatWell
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