Weight loss is a perennial pursuit in the United States, yet obesity is at its highest level ever. The diet pendulum has swung from high-protein diets to high-carbohydrate diets and back again -- all of which might lead one to ask, Are there really any successful weight-loss strategies?

The answer is yes. But they have less to do with restricting your intake of one particular type of food, such as proteins, fats or carbohydrates, as they do with controlling portion size and getting enough physical activity.

Americans embraced low-fat, high-carbohydrate diets and fueled the tremendous growth of fat-free packaged foods over the past 10 years only to discover that they were not losing weight. Why? Contrary to popular belief, a fat-free label was not a ticket to consume unlimited quantities.

As a result, high-protein diets have resurfaced and gained a large following in the last few years. While they often result in a quick weight loss, these diets are associated with an increased risk of heart disease, some cancers, osteoporosis and kidney damage. Weight loss usually occurs on these diets because they are low in calories and portions are carefully controlled, but experts advise that they can be difficult to maintain as well as dangerous.

The best approach remains a well-balanced diet based on the Food Guide Pyramid, with close attention being paid to portion size. Many of us would be surprised to learn that our typical single serving is actually equivalent to two or three servings on the Food Guide Pyramid.

Experts also advise that you track total caloric intake. The equation for weight loss is simple: consume fewer calories than you expend. This brings us to exercise. For long-term weight-loss success, physical activity must be part of the equation.

In addition to aerobic exercise, which burns excess fat, your program should include strength training, which increases muscle mass and your metabolism. The following exercise uses a resistance tube to target the larger muscles in the lower body.

Slip one handle of a resistance tube through the other to form a loop that you can place around your right ankle. Place the other end of the tube under your left foot. Keeping your feet about 12 inches apart, place your right foot behind your left leg. Bend your right knee and lift your foot up behind you. You should feel resistance from the tube as you do this.

Repeat the movements 10 times before switching to the opposite leg. Continue alternating legs for two to three sets as desired.

(c) 2000, Judi Sheppard Missett, Jazzercise, Inc. Distributed by Los Angeles Times Syndicate