Caffeine can stimulate the central nervous system, providing a boost of energy many people rely on each morning.1

Energy drinks, coffee, tea, soda, and chocolate all contain caffeine, and this chemical is said to speed up the body’s metabolism, meaning you’ll burn more calories.2 Some evidence has suggested that caffeine may be associated with weight loss, but researchers are still trying to understand its mechanism.3

Caffeine's potential to speed up metabolism may be one reason caffeine has been included in the weight loss conversation. It’s also been touted as an appetite suppressant and is often used in weight loss supplements.41

“For some people, it may increase their total calorie output. But we wouldn’t expect it to be a drastic shift and we wouldn’t expect it to have major impacts on their weight or their calorie balance for the day,” said Colleen Tewksbury, PhD, MPH, RD, an assistant professor in nutrition science at the University of Pennsylvania School of Nursing.

Does Caffeine Really Help With Weight Loss?

The research on caffeine offers some interesting findings, but there's not enough evidence for nutrition experts to say that drinking coffee would lead to significant weight loss.

Animal models and short-term human studies have shown that caffeine might help with weight loss, according to Andrew Odegaard, MPH, PhD, an associate professor of epidemiology and biostatistics at the University of California, Irvine, Program in Public Health.

"Some mid-term trials of caffeine ingestion or coffee intake have shown surprising effect on modestly lowering body fat,” Odegaard told Verywell.

One small study from 2020 found that people who drank four cups of coffee each day over the course of 24 weeks lost some fat mass compared to those who were given a placebo, non-caffeinated beverage. However, the authors noted that this fat mass loss was “modest” and the coffee group generally had a higher body fatness than the placebo group.3

 

“Coffee drinkers who consume regular coffee shouldn’t expect any miraculous changes in body weight due to consumption,” said Odegaard, whose research focuses on obesity and dietary intake.

Another recent study found that having a genetic predisposition to slower caffeine metabolism—and as a result having higher amounts of caffeine in the blood—was associated with a lower body mass index (BMI), fat mass, and type 2 diabetes risk.5

Tewksbury, who specializes in adult obesity management, said scientists can use this type of study to understand why people respond to caffeine differently, but it can’t be used for population-based recommendations since people aren't getting genetic testing to determine if they have the gene that predisposes them to a slower caffeine metabolism.

“It helps us have a greater and deeper understanding of nutrition science and metabolism,” Tewksbury said.

Does Caffeine Boost Exercise Performance?

Besides weight loss, caffeine has also been promoted as a performance enhancer. Many pre-workout drinks contain caffeine and there’s some evidence to back this up.6

A 2019 review published in the British Journal of Sports Medicine concluded that there are benefits to taking caffeine to boost muscle endurance, muscle strength, anaerobic power, and aerobic endurance. However, more studies are needed, especially since the findings “apply mostly to men and young individuals.”6

According to the International Society of Sports Nutrition (ISSN), taking 3–6 mg/kg body mass of caffeine may improve exercise performance, and the best time to take caffeine depends on the form of the supplement. But it's worth noting that some of the authors of the ISSN statement declared conflicts of interest because they're on scientific advisory boards for some sports supplement brands.7

“There’s good evidence that caffeine or coffee may increase exercise performance in a lot of people under certain conditions,” Cindy Fitch, RD, PhD, associate dean of research and nutrition for West Virginia University Extension, told Verywell.

However, she said a variety of factors, like what time you take the caffeine, how much you take, your genetic makeup, and the type of exercise you do, could all impact how your body reacts to the supplement.

“It’s not something that one size fits all,” Fitch said.