The idea of pot smokers as chubby middle-aged dudes who live for junk food and couch surfing is fast becoming obsolete. Plenty of regular cannabis users are far from fat, unhealthy, or lazy. A growing contingent of elite athletes — ultrarunners and triathletes among them — insist marijuana actually helps them stick to their diet and exercise regimens and keeps them trim. Some even swear weed has helped them shed pounds.
They may be onto something. Although the science on weed and weight loss is still emerging, some research suggests marijuana might play a small role. Weed is not a stand-in for healthy diet and exercise — not by a long shot. But marijuana use also isn’t a straight path to becoming an overweight unhealthy mess. Here’s what the science has to say.
The Science of Weed and Weight Loss
There is solid scientific proof that THC, the intoxicating cannabinoid in pot, indeed stimulates appetite in many people. That’s why it’s often given to chemotherapy patients who otherwise feel too sick to eat. THC binds to and activates CB1 receptors, part of the endocannabinoid system, which are located in the stomach, small intestine, and parts of the brain that monitor food intake and enhance eating pleasure.
“CB1 is basically your weight gain receptor,” says Thomas Clark, Ph.D., cannabis researcher and chair of biological sciences at Indiana University South Bend. “It is the main one that increases appetite, affects how fast you store the food you eat and reduces your metabolic rate to preserve the calories you consume.”
Considering these effects, one could reasonably assume that regular marijuana use would lead to weight gain. Some studies do support this theory. However, the overall evidence is conflicting, and plenty of other research suggests the exact opposite may be true.
For example, a 2011 study showed that people who use cannabis at least three times a week are less likely to be obese than non-users. Similarly, research published in 2013 revealed that marijuana users had better insulin control and smaller waist circumferences. More recently, a 2019 study demonstrated that, over the course of three years, marijuana users maintained lower body-mass indexes than nonusers, something past research has found as well.
On its face, that’s some pretty compelling data in favor of weed and weight loss. But these studies must be taken with a grain of salt. They all establish a connection between cannabis and a better body — but they don’t prove marijuana use is the reason for these outcomes. There could be other factors at play.
“All sorts of correlational effects probably contribute to these results,” Clark says. “For one thing, pot smokers skew younger, so they may weigh less. Maybe these marijuana users also used more tobacco, which is associated with weight loss. Then there are people who are heavy, start smoking pot and just feel better, so they lose weight and attribute it to marijuana when there may not be any physiological effect.”
Additionally, many pot smokers drink less booze, a definite contributor to weight gain. Marijuana also eases stress for many people and helps them sleep better, both of which are linked to lower BMI. There is also the pain management factor. If pot eases muscle aches and pains, it may help you stick to your workout plan or even train harder, as some athletes claim it does.
How Marijuana May Help You Lose Weight
Regardless of all the potential cofactors aside, some researchers believe marijuana still might, in fact, have a direct physiological impact on weight. Clark is one of them. In 2018, he and his colleagues published a paper that, based on data from 17 large-scale studies, lays out a plausible explanation for the lower BMI and obesity rates among cannabis users.
Clark breaks down their theory like this: THC initially stimulates the CB1 receptor, which increases appetite short-term—but this effect doesn’t last. Over a 24-hour period, he says the receptor becomes less active, likely leading people to consume fewer calories overall. Meanwhile, evidence suggests THC ramps up metabolism over time. So, based on this theory, even if you indulged the munchies after smoking a bowl, your increased metabolic rate would counteract the effect by burning through those calories quicker than if you weren’t a pot smoker.
You wouldn’t need to smoke a ton of weed to reap these benefits, either. Clark insists even once a week may be enough to keep the CB1 receptors running on low and metabolism revved.
However, he is quick to point out that this is still just a hypothesis. To know for certain whether THC has this impact on weight control, Clark says we’d need rigorous human clinical trials. Researchers would have to gather a bunch of people with identical diets and lifestyle habits, divide them in half, give one group pot and the other not, then monitor them over a long stretch of time.
This kind of study won’t happen anytime soon, however, because weed is technically still illegal in the U.S. and laughably still deemed a Schedule I narcotic, which severely inhibits research. Complicating matters, Clark says plants like marijuana are notoriously hard to study because they’re complex organisms that vary significantly in makeup from strain to strain.
So, for now, the best we have are theories, and Clark’s seems pretty sound. That said, he does not advise making marijuana your number-one weight-loss tool: “I think cannabis can help if the side effects are tolerable, but you’re better off focusing mainly on diet and exercise.”
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