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INHERITED `OBESITY GENES’ INCREASE TENDENCY TO BE OVERWEIGHT

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QUESTION: Both of my parents are fat and I have had problems most of my life trying to control my body weight. What is the role of genetics in weight control? Thank you for your answer in advance. I enjoy reading your column.

ANSWER: An article in Science News on Nov. 18 addressed this issue. Researchers at the University of Iowa studied 277 high school students and 1,303 of their siblings, parents, aunts, uncles and first cousins. They calculated each person's body mass index as a measure of obesity and used statistical methods to see whether genes appeared to control obesity in the families studied.They found that family weight patterns fit a model in which there is one highly influential gene code for either obesity or slimness, while other genes play lesser roles. In this model, the gene coding for obesity appeared to be recessive, manifesting itself when inherited from both parents. This means that if you inherit the gene for obesity from both parents, you stand a greater chance for being obese than if you inherit only one obesity gene and one slimness gene, or two slimness genes.

Based on the findings of this study, about 5 percent of the population carry two obesity genes, 34 percent carry one of each and 61 percent carry two slimness genes.

It is important to realize that carrying two obesity genes does not mean that you have to be obese; it simply means that you will have a greater tendency to become obese. It would be extremely important for people who carry obesity genes to eat properly and exercise regularly because they also face a host of cardiovascular risk factors, including significantly higher blood pressure and lower levels of high density lipoprotein, the transport molecule that carries cholesterol from the blood to the liver for excretion. According to this article, even those with slimness genes can become obese if they are inactive and eat too much or the wrong kind of food.

The Iowa researchers have not identified any specific obesity gene, but one candidate is the gene coding for lipoprotein lipase, an enzyme that helps the body store fat. Higher levels of this enzyme have been found in certain overweight people, as well as in some people who are on a restricted intake of calories.

QUESTION: I have been working out with surgical tubing instead of weights to develop strength. What is your feeling about this?

ANSWER: The basic principle for gaining strength is called the overload principle. This principle states that to gain strength, you must overload the muscle (that is, you must place more than normal stress on it) so that it will feel a need to become stronger to handle the increased stress. How you exert the overload is not as important as the fact that you do overload.

The only problem with surgical tubing is that the load increases as the tubing gets longer, so you might not get an even overload throughout the full range of motion. Most modern strength training equipment tries to match the resistance to the muscle so that strength gains occur at any angle of movement.