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Stimulating Environments Helps Give White Fat the Calorie-Burning Power of Brown Fat
Recent years have brought a lot of buzz about brown fat, which is known to burn more calories than its more ubiquitous cousin, white fat. Brown fat is found almost exclusively in young animals and those who live in cold climates, since its purpose is mainly to generate body heat. Its existence in adult animals has only been demonstrated in the last few years, and since that time, many researchers (and regular folk) have hoped that understanding how it works might lead to effective weight loss therapies.
Now, a team has found that the amount of brown fat in adult mice can be increased, not only through drugs, but through the environment in which the animals live. The team had previously found that animals who lived in an "enriched environment" – with toys, tunnels, wheels, mazes, and the like – had more growth of new neurons than animals who lived in plain old lab housing.
In the new study, the researchers had animals live in either the enriched environment (EE) or typical housing (controls). They found that after four weeks in the respective environments, the EE mice had an almost 50% reduction in abdominal fat compared to controls. To determine whether this was simply a result of the fact that they were more active than controls, the researchers gave another group of mice access to a wheel, but not to an EE. These mice did lose weight, but not nearly as much as the true EE mice.
The team also found that when animals were fed a high-fat diet, the EE mice gained 29% less weight than control mice. The EE mice also had higher body temperatures, which hints at the mechanism: these mice were likely burning more calories than control mice. But why?
The researchers outline the likely process: A physically and mentally stimulating environment promotes the expression of bone-derived neurotrophic factor (BDNF), which normally influences energy expenditure and food intake (along with a host of other cell process, including those involved in learning and memory). In EE mice, the over-expression of BDNF triggers genes specific to brown fat to be turned on in white fat, while at the same time suppressing white fat genes. To verify that this was indeed what was going on, the researchers used genetically engineered mice who lacked the BDNF signaling pathway, and showed that in these animals, the brown fat conversion process was inhibited.
Lead author Michael J. During says, "One of the holy grails of obesity therapy is to understand how to switch white fat to brown fat, and this study describes a new way to do exactly that. Our findings suggest that we can potentially induce this transformation by modifying our lifestyle or by pharmacologically activating this brain-fat pathway." The researchers are now working to determine which specific factors in the EE are most important in the phenomenon.
Of course, the big question is, will it work for humans, too? The answer is likely yes, but future studies will need to confirm it. In the meantime, given the many benefits of living a mentally and physically stimulating life, it can’t hurt to work on enriching your own environment — aside from boosting happiness, it might just help you shed a few pounds, too.
The study was carried out by a team at Ohio State University, and is in the September issue of the journal, Cell Metabolism.
September 7, 2011