One of the most important ways to preserve good health is to control your weight. By shedding pounds, overweight people can reduce their risk of type 2 diabetes, high blood pressure, and coronary heart disease (CHD). Losing weight may lower levels of low-density lipoprotein (LDL) cholesterol, which is often referred to as "bad" cholesterol. Losing weight can also lower levels of triglycerides and even increase high-density lipoprotein (HDL) cholesterol, referred to as "good" cholesterol. In addition, weight loss can help reduce the risk of osteoarthritis and gallstones.

In theory, weight control is a simple matter of balancing energy intake (the calories supplied by food) with energy output (the calories expended by physical activity and metabolism). To lose weight, you need to expend more energy than you take in. In practice, however, the task is clearly not that simple. While the basic principle of energy balance remains true, several mechanisms--genetic, metabolic, and environmental--control how much you eat and how your body uses and stores energy.

Even if some of the components involved in weight regulation are beyond your control, however, other factors within your control have a significant impact on your weight. Here's what you need to know to lose weight and keep it off:

1. How does the body use and store energy?
2. What factors affect body weight?
3. What are the medical consequences of obesity?
4. Are you overweight?
5. What's the best way to lose weight and keep it off?
6. Which diet plan is right for you? (PDF)
7. What are the medical and surgical treatments for severe obesity?