Dopamine could be to blame for people's reduced motivation to exercise

The New Year is here and for many of you that will mean a new exercise regime designed to get you into shape and improve your overall health.

For some people, though, sticking to a disciplined program of physical exercise is one of the hardest resolutions they can make because a lack of motivation gets in the way.

But now new research sheds some light on why many people, despite understanding the benefits of regular exercise, find it hard in practice to stay physically active.

Researchers from the Diabetes, Endocrinology, and Obesity Branch at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), led by Alexxai V. Kravitz, focused on why obese animals also have a hard time carrying out physical activity. They found that a dysfunction in obese rodents' dopamine systems might help explain why.

Mice fed on a high-fat diet started gaining significantly more weight than mice fed on a normal diet. They were also observed to have fewer movements; spend less time moving; and were slower when they did move, compared with the lean mice.

Most interesting of all was that the overweight mice's changes in movements did not correlate with body weight gain. Instead, the researchers found that a deficit in striatal D2R explained the obese mice's lack of activity.

"In many cases, willpower is invoked as a way to modify behavior. But if we don't understand the underlying physical basis for that behavior, it is difficult to say that willpower alone can solve it," said Kravitz.