Weed for Weight Control?
By Dr. Alicia K. Wilbur
Chances are that when you think about marijuana, you think about someone smoking a joint and craving junk food—the munchies. Indeed, cannabis has been shown in studies on laboratory animals to stimulate food intake, and it is known for its orexigenic, or appetite stimulating, effects in humans as well.
To date, seven states have approved cannabis to treat anorexia, prolonged lack of appetite, caused by a variety of debilitating conditions, including infections with hepatitis C or HIV viruses, inflammatory bowel disease and multiple sclerosis. Twenty states have also approved cannabis for treatment of cachexia, a wasting syndrome associated with chronic illnesses such as cancer, AIDS, diabetes and multiple sclerosis. In light of the orexigenic effects of marijuana, it may seem counterintuitive to consider it as a potential mechanism for weight control, but there is evidence from both laboratory animal and human-based studies that compounds in cannabis may help prevent.
Several studies, in multiple human populations, have found that cannabis use is associated with lower prevalence of obesity. For example, a cross-sectional study of more than 41,000 adults, comprising five different racial/ethnic groups, found that prevalence of obesity was significantly lower in cannabis users than in nonusers. Interestingly, there appeared to be a dose-response effect of cannabis on obesity—the groups that had higher cannabis use also had lower prevalence of obesity. Although sex, age, and use of alcohol and tobacco are also associated with obesity, these factors were taken into account in the study. The authors of the report were able to conclude that “even if cannabis consumption increases appetite, people using cannabis are less likely to be obese than people who do not use cannabis.”
We should probably take a moment here and clarify what we mean by “obesity.” It is not just a case of being a few or even several pounds overweight. According to the World Health Organization, obesity is a term used for abnormal or excessive fat accumulation that presents a risk to a person’s health. For most adults, obesity is often assessed using the body mass index, which is based on an individual’s weight and height and is an indirect indicator of body fatness. Normal BMI for an adult is considered to be 18.5 to 24.9, while overweight is 25-29.9. Someone with a BMI of 30 or more is considered obese.
Obesity is associated with serious health consequences such as heart disease and stroke, diabetes, osteoarthritis and certain types of cancers. The WHO estimates that in 2014, over 600 million adults over age 18 were obese, representing about 13% of the world’s adult population. Obesity isn’t just an issue for adults; in 2013, the WHO reported 42 million children under 5 years of age were obese.
There can be many causes for obesity, but in most cases an energy imbalance is at the core of the issue—more energy is taken in than put out in daily activities. In general, obesity is treated with increased activity and modification of diet, but this is easier said than done. Particularly for cases of morbid obesity, the United States National Heart, Lung, and Blood Institute indicates that supplemental weight-loss medications may be helpful or even necessary. Unfortunately, there are side effects to these medications, some of them so severe that the drugs have been pulled off the market. Fenfluramine, dexfenfluramine, and sibutramine, for example, all had to be taken off the market in the United States because of elevated risk of cardiovascular problems, in some cases fatal.
For cases of morbid obesity in which other treatment options have not been successful, weight-loss surgery may be required. The common ones are gastroplasty and gastric bypass, both of which limit the amount of food and liquids the stomach can hold. These surgeries can be risky, may have prolonged side effects, and lifelong medical follow-up is required.
This is an area where cannabis may be able to help. In a controlled study of laboratory mice, the cannabinoid THCV was found to reduce weight and appetite, and modulated feeding behaviors. In a recent study of adult humans, researchers at the University of Reading hypothesized that augmenting weight control measures with a drug that modulates the brain’s regulation of eating behavior might help to control food intake. They reported in a newly published article in the International Journal of Neuropsychopharmacology that treating 20 healthy adults with the cannabinoid THCV caused an increase in responses to aversive food stimuli and subsequently made the people not want to eat a pleasant food like chocolate.
This is an exciting finding, not only because THCV helped with control of eating, but also because the reward processing functions of the brain were still left intact. In the past, drugs that reduce reward processing have been associated with depression as a serious side effect, and Rimonabant, a drug that was used for a time in the European Union to treat obesity, had to be pulled from the market due to increased risk of severe depression and suicidality following its use. The cannabinoid THCV, and compounds like it, may thus hold promise for development as anti-obesity.
Before we get too excited about the weight control possibilities of cannabis, it is important to note that, as with many potential drugs, some adverse effects have also been reported. In particular, cannabis use may be harmful to the developing brain; in terms of weight management, cannabis use in adolescents 12-18 years of age has been associated with increased risk of future obesity. Despite these concerns, given the serious health consequences of obesity as well as the relative ineffectiveness and severity of the other available treatments, further exploration of the weight modulation properties of cannabis seems more than reasonable.
The WHO estimates that worldwide obesity has more than doubled in the last 35 years, alongside an increase in the associated health problems. It would be prudent for us to now increase our research efforts and funding into marijuana for weight.