MOVE OVER, Whole30. The newest weight-loss plan is the thing you hid from your parents in high school. Some scientists are linking tetrahydrocannabinol—or THC, the psychoactive compound in marijuana—with weight loss.
“People assume marijuana users are heavier because it stimulates appetite,” says Tom Clark, chair of the biological sciences department at Indiana University South Bend. Clark and his team analyzed 17 studies that included almost 156,000 participants, and found that pot users were lighter than the drug-free. And their body mass index (BMI) is 7 percent lower on average—for a 6-foot guy, that’s a 15-pound spread. Most interesting, pot users are 30 to 35 percent less likely to be obese.
THC seems to bump metabolism over time, so even if there’s an initial hit of the munchies, the metabolism boost compensates—and then some. “And if modern strains have lost the munchie effects, but increased metabolic rates remain, I would think the effects of reducing obesity would be even greater,” Clark says.
And you don’t have to be a frequent smoker to lose pounds. A one-time user bumps his metabolism for up to four weeks, so getting high a couple of times a month can get you noticeably trimmer, studies revealed.
The exact dose needed is unclear, but THC is a must, as opposed to its more widely legal, nonpsychoactive counterpart cannabidiol (CBD). The thinking goes that our modern American diet is too high in omega-6 fatty acids, which come from sources like vegetable oil and butter. In excess, omega-6 can cause inflammation in the body. It also overstimulates a receptor called CB1R, which causes increased hunger and makes food taste better, decreases metabolic rates, and encourages fat storage. THC is able to “talk” to the CB1R receptor and help restore homeostasis, Clark says. In other words, it may help reduce hunger and weight gain.
THC may also improve the gut biome, which also affects weight. Obesity is linked to higher levels of a group of bacteria called Firmicutes, and lower of another, Bacteroidetes. In an animal study from the University of Calgary in Canada, obese mice on a high-calorie diet were given THC. Their gut bacteria levels normalized, and they stopped gaining weight.
Still, pot can’t undo bad eating. “If you want to lose weight, you can’t keep a diet high in fat, sugar, and artificial sweeteners,” says Myron Szewczuk, a biomedical researcher at Queen’s University in Ontario, Canada.
Not everyone’s buying it. “The data that cannabis causes weight loss is not solid,” says Diana Martinez, a psychiatry professor at Columbia University Medical Center in New York. “There are animal studies, but the human research is based on self-reporting, so there’s no way to know how much they’re taking. To prove the theory requires a study that gives some people THC and others a placebo.”
Martinez is not necessarily anti-pot. She says it has treatment potential for debilitating conditions—like multiple sclerosis, chronic pain, and Crohn’s disease—that need more treatment options. But in the U.S., regulations governing THC in research need to loosen before large-scale human studies can happen.
Unless you live in a state where recreational marijuana is legal, this diet advice will be hard to follow. And since definitive science is lacking anyway, you’re not a buzzkill if you choose to stick with a good diet and exercise.