Updated June 25, 2002

Obesity, Type 2 Diabetes, and Physical Activity
What's the Connection?

by Richard M. Weil, M.Ed., C.D.E.

Genes may also affect the hormones that control satiety (feeling full), appetite, metabolism, and fat distribution. We all know someone who seems to eat as much as he likes and never gains a pound. That's at least partly genetics, but there may be other factors at work here, too. In one study, researchers fed a group of people 1,000 extra calories per day for 80 days to get them to gain weight. The outcome was that everyone gained a different amount of weight (the range was 9-32 pounds), even though they all consumed the same number of calories and did similar levels of planned activity.

How is this possible? The researchers discovered that some people were more active at rest than others. They actually fidgeted more, and this accounted for a good deal of the variation in weight gain. The other factor probably has to do with the presence or absence of so-called "thrifty" genes. Thrifty genes are programmed to store fat efficiently—a vestige of the Stone Age, when the body stored fat if food was plentiful in the event that the next season might bring famine. Some of us, it seems, have retained these ancient genes designed for storing fat efficiently. The problem is that we live in an era and an area of the world where there is almost always abundance and never famine, so our stored fat never gets used.

In addition to there being plenty of food in our environment, Western society has evolved to the point where physical activity is a minimal part of our daily lives. Fewer jobs require physical exertion, and we rely more on automobiles and public transportation than on our legs to get around. In fact, over 75% of all trips in the United States that were less than one mile were made by automobile in 1995.

Even if we wanted to walk more, there are plenty of reasons not to. People tend to work long hours these days, and there seems to be little time left to take care of ourselves and our families. When we do have leisure time, there are many claims on our attention, such as television and computers. The conveniences and temptations of modern life may simply be too much competition for taking a walk to the store, riding a bike, pushing a lawnmower, or washing the car by hand. But if our lifestyle is contributing to the rising rates of obesity, then reversing the trend almost certainly means changing our lifestyle. Are we willing to do that?

Reversing obesity

Although there is no cure for obesity, there are ways to treat and manage it, including dietary changes, increased physical activity, behavior therapy, and medication. Surgery is an option for the most obese individuals (BMI greater than 40 kg/m2 or BMI greater than 35 kg/m2 with risk factors).

Most people can expect to lose 10% to 15% of their body weight through diet, exercise, and behavior change techniques (although some lose more), and a loss of even 10% of body weight will significantly reduce weight-related health risks. However, 95% of people who lose weight regain all of it within five years, and some gain back more than they lost in the first place. How much weight is regained depends a lot on diet and physical activity. Research shows that people who lose weight but don't begin or continue a program of physical activity regain most if not all of their weight in less than nine months. Those who are active tend to maintain their weight loss.

Many scientists believe that obesity begins sometime in the early stages of life, so working with children and their parents to prevent obesity or treat it early makes a lot of sense, particularly since it is so hard for adults to lose weight and keep it off. The limited amount of research that has been done in this area shows encouraging results, but the research is recent, and long-term results are not yet available.

Richard Weil is an exercise physiologist and a consultant to the Naomi Berrie Diabetes Center at Columbia Presbyterian Medical Center in New York City.

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