The science behind obesity
special to the daily
Approximately 70 members of the community gathered Jan. 25, at Silverthorne Town Hall for a lively conversation about “New Research on the Metabolic Health Impact of Weight Change” with Dr. Steven E. Shoelson, professor of medicine at Harvard Medical School and head of the cellular and molecular physiology section of Joslin Diabetes Center in Boston. The free public event was jointly hosted by Keystone Symposia and Cafe Scientifique. An internationally recognized leader in diabetes research, Dr. Shoelson was in the county to speak at Keystone Symposia’s scientific conferences at Keystone Resort on “Adipose Tissue Biology” and the “Neuronal Control of Appetite, Metabolism and Weight.”
As most know, obesity has reached epidemic levels in the U.S. and many other industrial countries. Its growing prevalence in children – no doubt partly due to the fructose in sodas and many foods and to the decline in school physical education – is particularly disturbing. Thirty percent of those who are obese, according to Shoelson, will get type 2 diabetes, which is distinct from type 1 diabetes that individuals typically have from birth. Weight gain also has numerous other negative health impacts, including promoting cardiovascular disease, respiratory problems such as asthma, arthritis and fatty liver disease. The latter is the second most common reason for liver transplants after hepatitis C.
Shoelson shared his lab’s interesting findings that an inflammatory response occurs when adipose fat cells insinuate themselves into muscle. White blood cells from the immune system congregate in the muscle tissue. While the exact pathway linking this response and the promotion of insulin resistance (the cause of type 2 diabetes) is not yet known, experiments have shown that artificial measures to minimize the inflammation do reduce the incidence of diabetes. And some researchers think that this same link between fat and inflammation might be at work inducing certain cancers that occur at a higher rate in those who are obese.
Fortunately, says Shoelson, losing weight reduces the inflammation just as quickly as it occurred, and, in the same manner, type 2 diabetes can be reversed. Losing weight, of course, is not always easy. For one thing, there is a tendency for the human body to slow down the metabolic rate as an individual consumes less, thereby counteracting the attempt to lose weight and often causing weight lost to be regained. From an evolutionary standpoint, this may be because the human body was geared for regular periods of famine. Now that many of us have constant food surplus, nature doesn’t quite know what to do with us!
Likewise, a hormone called leptin that tells the hypothalamus when we are full may not have as much effect in some individuals. And gaining weight actually compounds an individual’s resistance to this useful hormone. Additionally, as we age, metabolism tends to slow.
Why some overweight people contract type 2 diabetes and others do not is also thought to have a genetic link. Because of genetics, some individuals’ ability to produce insulin may reach a finite point, making them more prone to develop diabetes. Insulin is vital for moving dietary glucose from the bloodstream into tissues like liver, muscle and fat. When insulin is not produced in the pancreas, its primary natural source, or if other tissues are no longer responding to signals from insulin, then the resulting very high levels of glucose in the bloodstream lead to damage in many places throughout the body over time.
At an audience member’s inquiry, Shoelson touched on the interesting debate concerning brown versus white fat. Scientists have found that mice use energy-burning brown fat tissue (as opposed to energy-storing white fat) to keep warm; in humans, turning down the thermostat several degrees or taking a very cold bath for a couple of hours may induce a small amount of weight loss by prompting the conversion of white to brown fat. These are relatively recent hypotheses about which scientists have much more to learn.
In general, there is no substitute for maintaining a healthy weight by controlling caloric intake through diet, balanced with exercise to burn the calories. In Summit County and Colorado at large, individuals are rarely at a loss for physical activities that have helped keep the obesity rate in our state the lowest in the country (Alabama’s and Mississippi’s, in contrast, are the highest). But when all else fails, some bariatric surgery has shown good results, while, like any surgery, posing its own set of risks. In fact, gastric bypass surgery that actually rearranges some of the internal abdominal pipes as opposed to just restricting food intake has in some cases immediately eliminated an individual’s type 2 diabetes, according to Shoelson. Liposuction, on the other hand, has very little proven health impact, and much of the fat removed is often regained.
Cafe Scientifique, founded and organized by Elmer Koneman, M.D., is planning various other meetings this year. Its June gathering will again be held in conjunction with Keystone Symposia on Molecular and Cellular Biology.
Based in Silverthorne, Keystone Symposia convenes 50+ scientific conferences annually on topics ranging from cancer to infectious disease to neurobiological disorders. More info at http://www.keystonesymposia.org.
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