LSU AgCenter Nutritionist Looks At Genetic And Physiological Obesity Factors

News You Can Use For April 2005

Obesity is an epidemic in this country. It is a chronic disease that is leading the huge increase in diabetes and other chronic diseases, according to LSU AgCenter nutritionist Dr. Heli Roy.

A recent study estimated that the total cost of obesity in the United States was $238 billion in 1999. Louisianians spend $1.3 million a year on obesity-related health care costs.

Body weight is regulated by a series of physiological control systems involving the central nervous system, sympathetic nervous system and hormones. A small increase in daily energy balance can result in large changes in body energy stores over time.

Obesity is a result of a combination of environmental pressures and genetic susceptibility. Environmental pressures include, in large part, an "obesogenic" environment. This refers to conditions that lead people to become excessively fat by eating too much of the wrong things (high-fat, high-sugar, palatable food) and not having enough physical activity.

Obesity has a genetic component. Prevalence of obesity is twice as high in those that have obese relatives compared to those who do not. The risk of extreme obesity is eight times higher in those who have extremely obese family members.

Why do we have a tendency to put on weight? Roy explains that during early years of human history, our genes evolved to conserve energy during times of famine, in the so-called "thrifty genotype hypothesis." Food was scarce and a lot of physical labor had to be done to get a meal.

Today, however, the thrifty genotype is a liability, since we have plentiful, rich food available in every corner store and quick stop not to mention the well-stocked grocery stores. We don’t have to do much physical labor today for food.

Obesity also may be due to environmental influences that the baby is exposed to in the womb in what is called "fetal programming." An abnormal environment in the womb such as food restriction, variations in insulin concentration, lack of critical hormones and excess calories may cause physiological changes in the developing fetus that later echo in the adult as obesity, hypertension or diabetes.

Roy says the hypothalamus, a small organ in the brain, has long been recognized as the key center in body weight regulation. Various biochemical and neural signals from the stomach and fat stores arrive at the hypothalamus, which controls calorie intake. The concentration of various hormones then influences the feeling of fullness or hunger and eating.

Energy expenditure is an important part of obesity development. Many obese individuals have lower energy expenditure than non-obese. They are also less fidgety. Obesity may develop from a decreased ability of individuals to increase spontaneous physical activity, particularly when they are overeating.

Obesity development is the association of many physiological and hormonal signals in the context of genetic makeup. The maintenance of normal weight is much harder for some than others and may involve a stricter adherence to a low calorie diet and increased physical activity.

The factors contributing to obesity were discussed in a recent "Journal of the Louisiana State Medical Society" by Dr. Steve Smith and Dr. Eric Ravussin of the Pennington Biomedical Research Center.

For information on related family and consumer topics, visit the FCS Web site at
Extension/Departments/fcs/. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.


On the Internet: LSU AgCenter:
Source: Heli Roy (225) 578-3329, or

4/22/2005 1:56:10 AM
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