My name is Eric Ravussin. I'm a professor at Pennington Biomedical Research Center in Baton Rouge, Louisiana. This morning [at the American Diabetes Association 20015 meeting], I presented an update on the role of brown adipose tissue in humans.[1] Brown adipose tissue was quite popular about 20 years ago because it was a major mediator of energy metabolism in rodents. However, it was believed that brown adipose tissue was only present in babies in very, very early life for thermal regulation. But 5 years ago there was a revival of interest in brown adipose tissue because it was found to be present in adults, too.[2] Brown adipose tissue has a very high metabolism and can therefore burn calories. There was hope that, by stimulating brown adipose tissue, we can boost up resting metabolic rate and energy expenditure.
A question that was asked was: Is brown adipose tissue an important target for pharmacology to treat obesity? I think that the answer is "no." We know that brown adipose tissue can burn calories. However, the amount of calories that can be burned by brown adipose tissue is about 50-100 calories. I think that the role of brown adipose tissue in weight management is more likely to be for weight loss maintenance. As you know, your patients have a tendency to regain the weight that they lose. If, in response to weight loss, one can stimulate the brown adipose tissue, it would help weight loss maintenance. I think that there is a big hope from pharmaceutical companies to target the brown adipose tissue.
Now, how do we increase brown adipose tissue? There are two types of brown adipose tissue. One type is found as masses of brown adipose tissue, mostly behind your neck and under the clavicle. The other type of brown adipose tissue is dispersed in white adipose tissue. There is hope to boost up the amount of brown adipose tissue within the white adipose tissue, and this would increase metabolic rate and help in weight loss maintenance.
People who have a higher metabolic rate are more likely to lose weight and are also more likely to maintain the weight loss. This is why brown adipose tissue is important. However, remember that the role of brown adipose tissue in rodents is mostly to maintain the body temperature at the desired level, 35-37ยบ C. When exposed to cold temperatures, there is an increase in brown adipose tissue metabolism and the burning of calories, and therefore the maintenance of body temperature. A question that I brought up this morning was: Is there a relationship between what we call cold-induced thermogenesis and dietary-induced thermogenesis? Probably not. It means that brown adipose tissue metabolism is going to be mostly important for the regulation of core body temperature and less likely in response to abundant food intake. This is why I think that although there is some hope, it's not going to be the magical bullet for losing weight. It is probably a good strategy for weight loss maintenance, similar to exercise. We know that exercise is not very good for weight loss, but it is excellent for weight loss maintenance. This is the best analogy that I can make for the role of brown adipose tissue. It is mostly useful for weight loss maintenance and less likely to be useful for weight loss itself.
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