To Your Health

How do 'thrifty genes' influence weight gain?

Q. I'm 15, and I'm fat. My parents and two older siblings are fat, and three of my four grandparents are fat. If being fat is hereditary, will I always be fat?

A. Although we don't usually know exactly why some people become fat and others don't, you can lose weight and keep it off with intelligent changes in your lifestyle. For some people, maintaining their proper weight is automatic, requiring no conscious effort at all, while for others it is a daily struggle that requires immense willpower. The goal of many nutritionists is to understand the real reasons for unwanted weight gain and make it easier for an individual to attain and maintain healthy body weight for a lifetime.

According to one theory, known as the "thrifty gene" theory, certain genes permit a more efficient use of food when food is scarce. These people are more likely to survive famine and live to have children. Unfortunately these same genes also lead to weight gain in times of abundant food supply. Problems arise when people bearing thrifty genes live in a situation where food is always plentiful.

America has not experienced any widespread famines lately, and currently we do have an abundant food supply, even though some of the foods we choose are not very healthy. For most Americans there is also little need to work physically hard to earn a living and little incentive to exercise. These circumstances lead to weight gain for almost anyone, but weight gain is even easier for people with thrifty genes.

It is likely that several genes are involved in weight control, and so a solution involving genetic modification will not soon appear. A person with thrifty genes will need to develop a lifestyle that is considerably different from the typical American lifestyle. For instance:

• Educate yourself for a career that will involve more than a little physical activity rather than a sedentary occupation.

• Learn which high-fiber vegetables are attractive to you, and develop the habit of choosing several servings of these foods each day. Whole grains and whole fruits are high in fiber but may have too many total carbohydrates for you to be able to emphasize these.

• Begin now to limit the highly refined high-carbohydrate foods so easily available in America, and reserve these for very special occasions. In particular, avoid refined sugar and refined grain products like white bread and pasta. Even fruit juices may have too much rapidly absorbed sugar for daily use.

• Investigate fasting, one of the most ancient healing techniques and one that may be particularly beneficial for people with thrifty genes. Unlike famine, which may last a very long time, fasting can be practiced for as little as one day at a time and as often as every other day. An article in the January 2005 issue of The American Journal of Clinical Nutrition describes the beneficial effects of 22 days of alternate-day fasting. Among the most significant changes was a drop in insulin level by more than 50%. Elevated insulin level is suspected to be one of the effects of thrifty genes and the root cause of type II diabetes and the weight gain that usually accompanies it.

The good news is that a genetic susceptibility to obesity does not mean that obesity is inevitable.

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