If you’re used to being a couch potato, new science says that you might just be digging your hold even deeper. Don’t wind up as a permanent one. Turns out the less you move, the less motivated you are to start moving. Common sense, right? Now, that common sense is backed up by hard numbers.
Scientists took a look at obese mice, and what keeps them obese. Turns out it’s largely a result of alterations made to the dopamine receptors in the mice’s brains. The study was published in the journal Cell Metabolism this month, and may shed a light on why it’s so hard for humans to stick with an exercise routine.
Alexxai V. Kravitz, the senior author of the study, says, “We know that physical activity is linked to overall good health, but not much is known about why people or animals with obesity are less active. There’s a common belief that obese animals don’t move as much because carrying extra body weight is physically disabling. But our findings suggest that assumption doesn’t explain the whole story.”
Kravitz, whose wheelhouse is Parkinson’s disease research, noticed a striking similarity in the behavior of obese mice and mice who had Parkinson’s. The observation led him to the hypothesis that dopamine dysfunction might be responsible for their weight problems.
“Other studies have connected dopamine signaling defects to obesity,” says Kravitz. “But most of them have looked at reward processing — how animals feel when they eat different foods. We looked at something simpler: dopamine is critical for movement, and obesity is associated with a lack of movement. Can problems with dopamine signaling alone explain the inactivity?”
Researchers fed two groups of mice two different diets. The control group was given a standard diet, and the experimental group was fed high-fat foods for a duration of eighteen weeks. The high-fat group started showing increased body fat by the second week, and by the fourth, they were more lethargic and moved more slowly when they were active. Interestingly, the high-fat mice started slowing down before the extra weight appeared.
When they looked closer, the scientists found that the obese mice had a deficit in the D2 dopamine receptor. Danielle Friend, one of the researchers, said, “There are probably other factors involved as well, but the deficit in D2 is sufficient to explain the lack of activity.”
If obesity is linked, as this research suggests, to dopamine dysfunction, it would hugely empower us to help people combat weight problems. It would also be a significant help to lifting the stigma associated with obesity, which is popularly believed to be a result only of inadequate willpower.
“In many cases, willpower is invoked as a way to modify behavior,” said Kravitz. “But if we don’t understand the underlying physical basis for that behavior, it’s difficult to say that willpower alone can solve it.”