Mice Don’t Gain As Much Weight if Given THC, Study Finds

Cannabis consumers tend to be a little leaner than those who don’t use the drug, and a group of researchers may have just figured out why.

The University of California, Irvine, research team noticed that adolescent mice injected with THC gained less adipose tissue (fat) when fed the same diet as mice not injected with the cannabinoid.

Even into their sober adulthoods, the mice that had been given THC were still partially resistant to obesity. In other words, their THC-teen ‘years’ kept them lean late into life.

But this thinness came at a cost. The researchers found that the THC-injected mice had enhanced thermogenesis and impaired stimulus-dependent lipolysis. This latter defect could affect the mice’s ability to mobilize stored nutrients needed for brain and muscle activity.

Pseudo-lean mice

Several studies have found that most regular cannabis consumers have lower BMIs than those who don’t use the drug. Other studies have documented that most cannabis smokers start their habit in adolescence.

Curious as to whether these two observations were related, the University of California researchers devised a study to see if THC-exposed, adolescent mice would be any leaner in later life than the THC-sober mice. And they were.

After accounting for their activity, size, and food intake, the researchers found that the mice given daily injections of THC gained significantly less weight than the rodents in the control group.

The researchers posit that the THC activated the mice’s CB1 receptors in their adipose tissue, restricting their ability to store fat.

This effect seemed to be lasting, as, by their young, sober adulthoods, the mice injected with THC still had relatively more lean mass than the mice in the control group. Even when they fed high-calorie diets, the ‘THC-mice’ gained significantly less weight than their counterparts.

These slender figures, counterintuitively, seemed to help the ‘THC-mice’ keep warm. After transferring both groups of mice to a cold room, the body temperatures of the mice decreased at similar rates. But, after a while in the cold room, the bodies of the mice injected with THC started to rise at a faster rate than the bodies of the mice that had never been given THC.

The researchers say this enhanced thermogenesis could be linked to a “blunted” ability to mobilize fat stores into energy.

On further inspection, the researchers were flummoxed to discover the adipose tissue of the ‘THC-mice’ had higher levels of certain muscle proteins (such as titin and myosin) than expected.

“The anomalous molecular landscape induced by adolescent THC exposure defies straightforward interpretation,” the researchers wrote in their paper, which was published in Cell Metabolism.

The researchers posit that the regular stimulation of the mice’s CB1 receptors in their adolescent years caused the rodents’ bodies to enter a lasting, dysfunctional period of homeostasis in which lipolysis is defective while thermogenesis and anabolic processing are enhanced.

“Whether a similar phenomenon occurs in adolescent humans, who also experience a rapid increase in adipose cell number and size during their teenage years, is an important question for future studies,” the researchers wrote in the discussion section of their paper.