Need more proof that being thin is a pleasure? A new study from the US Department of Energy's Brookhaven National Laboratory reveals that dopamine D2 chemical receptors - associated with pleasure, rewards, movement, and motivation - are decreased in the genetically obese, reports Science Daily.

The study compared brain images of genetically obese rats to those of lean rats, and found that dopamine receptors are more present in the latter group. Aging reduced the dopamine levels in both groups, but to a less significant degree in the lean rats.

What scientists have not yet been able to determine is whether people become predisposed to obesity because they have low dopamine levels, or whether a lifestyle of overeating causes dopamine levels to go down. What they have found is that restricting food levels raises the dopamine levels and theoretically counteract obesity - and possibly slow down the effects of aging in the process.

"Consuming fewer calories is obviously important for people trying to lose weight, plus improving the brain's ability to respond to rewards other than food may help prevent overeating," says neuroscientist Peter Thanos, the study's lead author. "This study also provides further evidence for the interplay of genetic factors with the environment in the development of obesity in our society."

Looks like you have no more excuses for putting off that new diet. Rats.