BOTTOM LINE TO WEIGHT LOSS

The bottom line to weight loss is to burn more calories than you consume all day. (The behavior isn't simple, but the equation is.) For example, if you eat 2,500 calories a day and only burn 2,000, you gain weight; if you eat 1,500 calories and burn 2,000, you lose weight; if you eat 2,000 and burn 2,000 you maintain weight.

It's true that there are several medical conditions, and medications, that can make weight loss difficult (see below). But even if one of those factors applies to you, you still need to burn more calories than you consume to lose weight.

The good news is this: You can lose weight with a very modest amount of exercise.
People lose weight all the time without exercise by reducing their caloric intake. But keeping the weight off without exercise is another matter. Many experts agree that exercise is the single best predictor of long-term weight control. If you lose weight and don't start exercising, there's a very good chance you will regain it. Here are some factors that can keep you from losing weight and/or cause weight gain:

Thyroid or adrenal gland problems.
Medications like antidepressants.
Stopping smoking.
Rapid weight loss. This can lower metabolism because the body senses it is starving and make it harder to lose weight. The decrease in metabolic rate is often due to loss in muscle (when you lose weight, approximately 25% of the loss comes from muscle), so lifting weights is a good idea.
Menopause (and premenopause).

If you think any of these things are factors for you, your doctor may be able to help.
Otherwise, patience, determination, regular physical activity, and attention to your diet are the keys to long-term weight control. Doing these things will give you your best shot at reaching your weight loss goals and keeping the weight off.