"The fact is that the price of leanness is eternal vigilance -- losing and keeping off weight requires a lifelong effort. It amounts to maintaining a constant, realistic balance between total calories consumed and total calories expended," said Dr. Hansen, a physiologist and psychologist specializing in obesity, diabetes and their age-related health complications.
Dr. Hansen, a professor of medicine and pediatrics, directs the USF Health's Center for Preclinical Research, which combines obesity, diabetes and aging research, and the Diabetes Complications Prevention Center. Her latest studies with rhesus monkeys have shown that lifetime calorie restraint to prevent obesity is the most powerful way to reduce age-related health problems such as high blood pressure and high triglycerides and to prevent or delay the progression of insulin resistance toward diabetes. Monkeys whose food intake was maintained in amounts to assure a constant healthy body weight were not only healthier; on the average they lived longer than their counterparts who ate as much as they wanted.
"Our studies have unequivocally demonstrated that if you prevent excess fat deposits in the body through excess calorie restraint, you'll improve health and postpone death," said Dr. Hansen, who is scheduled to present the findings Feb. 17 at the American Association for the Advancement of Science Annual Meeting in St. Louis.
She is quick to point out that scientific evidence does not support assertions that the epidemic of obesity is the fault of the obese themselves or a "toxic" environment that seduces people with super-sized menus and convenience food at every corner. "There's a tendency to enter into a 'blame the patient' approach of 'you did this to yourself and you can fix it,'" Dr. Hansen said. "That's unfair and inappropriate."
There is still much scientists don't know about the complex interaction of genetic and environmental factors that predispose some individuals to obesity while others seem to eat to their heart's content without packing on pounds. Dr. Hansen considers "single cause" hypotheses such as diet composition, inactivity and obesity genes alone as too simplistic. "Obesity is a continuum that develops early or late, quickly or slowly, with a heavy dose of genetic predisposition," she said.
Studies support the concept that each person has an age-related "set" point for weight somehow regulated by physiology and genetics. This may help explain why more than 95 percent of dieters who shed 35 extra pounds or more eventually regain the weight, Dr. Hansen said. "Basically, while your weight may fluctuate throughout life, your body's natural tendency is to return to its individually programmed body composition."
Dr. Hansen's team is working to understand the underlying mechanisms of obesity that might lead to new drugs that more specifically target centers in the brain, liver and muscles that regulate weight. These would include compounds, known as mimetic agents, capable of mimicking the benefits of calorie restriction without leaving a person feeling constantly hungry. "Until we have new calorie restriction mimetic agents we need to be more accepting of obesity and its consequences," she said.
And what about those who are not clinically obese, but nonetheless battle the bulge as they approach middle age and beyond? Dr. Hansen suggests setting realistic goals.
"I highly recommend the bathroom scale model of weight loss. If you see your weight creeping up, then cut back on your portions," she said. "A 10-percent daily reduction in the total calories you consume may produce a small, but at least sustainable, weight loss. And, even a modest approach to calorie restraint can have positive health benefits."