Magazine article Nutrition Health Review

Weight Loss, Cortisol, and Your Brain

Magazine article Nutrition Health Review

Weight Loss, Cortisol, and Your Brain

Article excerpt

Americans everywhere are struggling to lose weight-and to keep from putting those lost pounds right back on. For many, it is discouraging to have their best efforts fail while those of other dieters succeed.

Agricultural Research Service (A.R.S.) researchers at the Western Human Nutrition Research Center in Davis, California, are conducting studies that may provide new insights into the underlying causes of this disparity in dieting success.

Given America's obesity epidemic, such research is timely and relevant. The Centers for Disease Control and Prevention (C.D.C.) estimates that 35 percent of adults and 18 percent of children and adolescents ages 6 through 19 are overweight or obese. Both conditions are associated with increased risk of type 2 diabetes, cardiovascular disease, and other chronic disorders.

Chemist Nancy L. Keim, nutrition scientist Kevin D. Laugero, and their colleagues have looked at several factors that may affect weightmanagement success. Their analysis included assessing volunteers' patterns of decision-making and evaluating changes in their levels of cortisol-a hormone associated with stress.

The study volunteers, 29 obese but otherwise healthy women 20 to 45 years of age, were asked to eat all of their meals at the nutrition center, where food was prepared for them.

The research began with a 3-week baseline phase, during which the goal was to stabilize the volunteers' weight. This was followed by a 12week, reduced-calorie regimen intended to help the volunteers shed pounds. During this weight-loss phase, meals provided 500 fewer daily calories than the total each volunteer would have needed if the goal had been to maintain her weight.

Two exceptions were built into the study. During each of the two study phases, volunteers had an "all you can eat" evening meal. These buffet dinners were provided for each volunteer to eat privately to help rule out the effect that social pressure might have had on what and how much the volunteer chose to eat.

Weight Loss Variations

The amount of weight lost and the amount lost as fat instead of lean tissue (muscle or bone) varied widely among the volunteers. Volunteers lost anywhere from 0 to 27 pounds.

Dr. Keim said, "The variation occurred even though volunteers were essentially provided the same foods and were each shorted 500 calories a day during the weight-loss phase-with the exception of the buffet dinner."

This variation, along with findings from many other weight-management clinical trials conducted elsewhere, suggests that tomorrow's weight-loss strategies "may need to be evep more individualized to be more successful," Dr. Keim said.

Dieting and Decision-Making

For many people, dieting "involves an ongoing series of decisions," Dr. Keim noted. "We wanted to get a snapshot of volunteers' patterns of decision-making."

To do this, the researchers selected the Iowa Gambling Task (IGT), a test that is widely used to evaluate "executive function." This umbrella term encompasses decision-making, differentiating good from bad, being cognizant of current actions, and resisting the temptation of short-term, immediate rewards in favor of long-term benefits. These functions are thought to be handled in a region of the brain known as the prefrontal cortex. …

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