Get thin through social stress!

Brown fat burns energy, and leads to weight loss.  White fat stores energy and leads to weight gain.  Unfortunately for people trying to lose weight, brown fat is primarily found in babies or in adults after chronic exposure to extreme cold.  Indeed, figuring out how to turn white fat to brown is apparently the ultimate quest in obesity research.

But now researchers at Ohio State think they're on to something.  As reported here, a paper in the September Cell Metabolism describes a study that enriched the environments of lab mice.  They put 15-20 mice together in large containers that included exercise equipment, tunnels, toys, huts, a maze, and unlimited food and water.  Control mice, on the other hand, were kept in the usual lab environment; 5 to a small cage, no toys or treadmills, unlimited food and water. 

Key findings include the following:
* Enriched animals showed a significant reduction in abdominal white fat mass (49 percent less than controls).
* Exercise (running in a wheel) alone did not account for the changes in body composition and metabolism of enriched animals.
* Fed a high fat diet (45 percent fat), enriched animals gained 29 percent less weight than control mice and remained lean, with no change in food intake. Enriched animals also had a higher body temperature, suggesting that greater energy output, not suppressed appetite, led to the resistance to obesity.

The researchers interpret this to mean that the enriched social environment triggers the "hypothalamic-adipocyte axis", which in turn triggers the production of "brown-fat-like cells" within white fat.  The researchers report that the protein responsible is BDNF, or Brain-Derived Neurotrophic Factor.  According to a story on the BBC website, the idea is that the complex social environment, things to do, friends to do them with, is challenging, and maintaining a network of friends is stressful -- but in a good way.

This stress is a positive thing for the body, prompting it to produce BDNF and convert the white fat to brown, preventing it building up and causing obesity. 

(Though it is curious that recent research has suggested that it's our social networks that make us fat.  If we have friends who are overweight, we're likely to be overweight as well.  Apparently we need to choose our social networks carefully.  Just any old social stress won't make us thin.) 

The lead author is quoted as saying that he "hopes that his research will help to communicate the impact of social psychology on health in the future, and promote lifestyle changes as an alternative to highly invasive gastric surgery."  Though, he is a neuroscientist, and apparently is working on a way to stimulate BDNF production surgically.

Stripped to the biophysiological bare bones, this sounds potentially promising for people who are trying to lose weight but can't. Of course lifestyle changes are often hard for people to make, and harder to maintain.  Still, it's poignant that the interventions being contemplated as a result of this study are medical -- surgery and/or pharmaceutical ways to trigger BDNF production, rather than the obvious one; "enriching" our lifestyles to include the changes that are already well-known to reduce obesity.

Of course, whether any genes are involved in these responses, or whether this has any bearing on evolution or not, are unlikely to be seriously important, but one can predict that, if this finding is taken seriously, geneticists will be quick to jump on it....for reasons easy to see, and whether that's a good way to spend research resources or not.