Can Coffee Cause Weight Loss by Affecting Appetite and Digestion?

Can Coffee’s Effects on Appetite and Digestion Cause Weight Loss?

By Lori Youmshajekian

After sipping a morning cup of coffee, most people are jolted awake. Others might notice that the drink tames their hunger, too. Many people on social media are increasingly drinking their favorite pick-me-up to shed pounds. But studies are only beginning to unravel how caffeine and other compounds in coffee might affect weight.

Several dieting trends and recipes categorized under the nickname “the coffee loophole” have picked up steam since early this year, stirring a renewed interest in consuming coffee (or caffeine in general) to lose weight. These sources claim that adding household spices or commercial supplements to a cup of joe or even chugging the mixture within seven seconds of experiencing a hunger pang can enhance the weight-loss effect. Experts are still puzzling over this: Does coffee—and particularly caffeine—contribute to people losing pounds in the first place? And how long do any weight-loss effects last?

Coffee and other caffeine products have been rumored to be a quick, easy weight-loss fix. The rationale is partly linked to coffee’s ability to get the digestive system moving. The caffeine in coffee can ramp up muscle contractions in the colon that stimulate bowel movements. That means the digestive system clears its contents a little quicker than usual. Caffeine is also a diuretic, meaning it increases urine production, and peeing more causes a loss of water weight. These combined effects on digestion and water weight happen quickly after consuming coffee but are short-lived—they don’t cause permanent weight loss. Consuming coffee over longer periods of time, however, seems to bring on different effects.

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Drinking coffee regularly doesn’t lead to significant weight loss, but it may prevent weight gain—albeit modestly. The average person typically gains weight as they get older—about a pound per year through middle age—but avid coffee drinkers seem to experience less age-related weight gain. A 2023 study followed the coffee habits of more than 150,000 participants and found that drinking unsweetened coffee was associated with a modest reduction in weight gain over four years after adjusting for other lifestyle variables. With each additional cup, the coffee drinkers gained about a quarter of a pound less than their peers. Most people probably won’t feel such a small difference in weight, though. Other studies have reported similar results. “You’re still gaining weight; it’s just slightly less compared to the general population,” explains Frank Hu, chair of the department of nutrition at the Harvard T. H. Chan School of Public Health and co-author of the 2023 paper.

Coffee has also been linked to a small loss of body fat. In one study, people who drank four cups of instant coffee a day had 4 percent less fat mass. They also lost a small amount of their total weight after a period of almost six months. That’s compared with a placebo group that drank a beverage that looked and tasted like coffee and maintained similar diet and exercise habits.

Caffeine, the primary bioactive compound in coffee, appears to be one of the main drivers of the reduced weight gain. The compound is known to stimulate diet-induced thermogenesis—the energy used to digest, absorb and store nutrients from food. On average, people spend about 10 percent of their total energy expenditure processing food. Studies have shown that caffeine can increase that amount by raising a person’s metabolic rate. A higher metabolic rate causes the body to use more energy at rest. The digestive process speeds up, causing organs in the gut to use slightly more energy and burn more calories. Overall, this energy increase is small, however: coffee drinkers might burn 80 to 150 more calories per day, according to one short-term study. That’s equivalent to a few Oreo cookies—but those few extra lost calories can add up over time, Hu says.

Caffeine is also believed to stimulate the sympathetic nervous system, which regulates the body’s fight-or-flight response. It blocks receptors that bind adenosine, a neurotransmitter that triggers feelings of sleepiness and promotes relaxation. Caffeine then prompts physiological responses in the sympathetic nervous system such as increased heart rate and alertness. That, in turn, burns slightly more calories, explains Marilyn Cornelis, an associate professor of preventive medicine at Northwestern University. Caffeine may also increase fat oxidation—the process of breaking down fat stored in tissues for energy—which might explain why coffee consumption is associated with a decrease in fat mass.

Independent of caffeine, coffee also contains several polyphenols—a type of antioxidant—that might affect weight. Chlorogenic acid, the polyphenol that gives coffee its distinctly bitter taste and strong aroma, has been shown to help maintain stable blood glucose levels. Because food cravings can be related to blood sugar fluctuations, more stable blood sugar might also help regulate appetite, Cornelis says. The bitter taste itself could also play a role; there’s evidence that the gut senses bitter compounds and adjusts appetite hormones to reduce food intake.

Scientists are only beginning to understand how chlorogenic acid may enhance coffee’s effect on hormones that control appetite and hunger. One small study that followed 126 people who were considered overweight found that coffee had a regulatory effect on satiety hormones; people ate slightly less and felt fuller after drinking the beverage. After drinking coffee, participants had higher levels of serotonin, a brain chemical that, among other things, can suppress appetite, and lower levels of the hunger-inducing hormone ghrelin. These effects were stronger in those who drank the coffee blend that contained more chlorogenic acid. The evidence suggests that coffee might influence appetite and hunger, but it may vary immensely from person to person. So drinking coffee to immediately suppress a spike in hunger may not be a realistic expectation. Scientists are also still trying to understand whether additives such as cinnamon and cayenne pepper tangibly contribute to coffee’s modest weight-loss effects, but they say those ingredients are harmless to add.

Coffee’s effects on health overall appear to be beneficial—in moderation. Research has consistently linked long-term coffee consumption to a lower risk of type 2 diabetes, heart disease, improved cognitive function and even lower mortality. But upping coffee intake simply to achieve these effects isn’t right for everyone. “It’s not like more is better,” says Rob van Dam, a professor in exercise and nutrition sciences at the George Washington University. Drinking more than about 400 milligrams of caffeine per day might cause difficulty sleeping, more stress and some anxiety, he says. To put that in perspective, one shot of espresso typically has about 60 milligrams of caffeine, though popular coffee beverages can contain much more, depending on size and roast.

Flavored lattes or frappes high in sugar and cream counteract some of the benefits that black coffee has on weight management. “That’s kind of a no-brainer,” Cornelis says. “Sugar adds calories, and coffee is traditionally a calorie-free beverage.” She suggests drinking coffee with less sugar and cream instead.

Hu says that, overall, coffee may have a modest benefit for weight loss but advises against “unrealistic expectations that drinking a lot of coffee … will dramatically change your body weight.”