Michael Cala interviews nutrition expert and cancer-prevention specialist Moshe Shike, M.D. about obesity in America and what his thoughts are on why American obesity is such a problem.

Discovery Health: We all know obesity is a major health problem in America. It seems to defy resolution.

Dr. Shike: Obesity, to a large extent, is an avoidable condition that leads to a number of avoidable diseases: hypertension, heart disease, diabetes, arthritis and some cancers.

What I find interesting is a recent survey that shows twice as many people in the United States are concerned about the fat content of their diets as they are about the total number of calories consumed. This line of thinking leads to obesity no matter what food is eaten.

While many people may scrupulously avoid fats, meats or alcohol, they will consume large amounts of other foods. Or they will buy foods that read "Fat Free" on the label. That huge bowl of pasta, for example, or that fat-free cake or sweetened cereal may not have much fat, but each is loaded with calories. Excess calories that are not burned off through physical exercise cause weight gain.

The conclusion is overweight people should eat less and exercise more.

Discovery Health: So if people exercised, they wouldn't gain weight?

Dr. Shike: Along with consuming excess amounts of food, Americans do not engage in adequate physical activity. Too busy. Too much television. Too much internet surfing. This includes children, a surprising number of whom are sedentary, eat too much and eventually become obese.

The great majority of dieters tend to regain the weight they have lost within 12 months. It would be much easier to maintain weight loss if people exercised regularly: three to five times per week for about 30 minutes each. Physical activity should also be incorporated into everyday living. Exercise is good for health, makes people feel better and helps burn off excess calories.