First author

Today two-thirds of US citizens are overweight or obese. For the past 20 years, endocrinologist Michael Schwartz at the University of Washington School of Medicine has been unravelling the molecular and cellular mechanisms behind this trend. On page 289 of this issue, he reviews the brain's role in weight control. Schwartz talks to Nature about his work.

Are you an endocrinologist or a neuroscientist?

To be active or competitive in any scientific field, you have to wear a lot of different hats. Obesity research is a multidisciplinary endeavour. People come to it from different backgrounds, but none will be optimal on its own.

How did you become interested in obesity?

When I finished my medical training at Rush Medical College in Chicago in 1987, I decided to become an endocrinologist. I did a fellowship with Daniel Porte at the University of Washington, who was interested in the relationship between insulin signals in the brain and diabetes. He became convinced that body weight is regulated by hormones acting on the brain. I was captivated by the idea that obesity is a problem of regulation rather than will power.

How has the patient population changed since then?

We see heavier and more medically complicated patients. It is becoming routine to see patients over 227 kilograms in weight.

Has scientific progress kept up with the rise in obesity?

We have made tremendous progress in our scientific understanding of obesity. The delay is in translating this knowledge into clinical practice. It is clear that the integrity of the brain circuits that regulate body weight can be compromised by a nutrient-excess environment. If cells are continuously presented with an excess of glucose or other nutrients, this will cause a dysfunction in many cell types, undermining the sensitivity of brain circuits.

Are you optimistic that the obesity trends can be reversed?

What I envisage in the next ten years is that instead of having two slightly effective drugs there will be ten different types. Each drug may not be all that powerful on its own, but we will be able to use combinations of drugs to target compensatory pathways.

When you take a bite of food, do you think about what is happening in your brain?

Yes of course. After spending so long in this field there is a part of my brain that is always thinking about that. But for me it is more out of intellectual curiosity than concern.