The metabolic rate is simply the rate at which you use up energy as in calories. The higher the metabolic rate the more calories you burn, the better the weight loss. The lower the rate the fewer you burn. This can depend on a number of different factors.
Metabolism rates can change, either going up or down. Such changes are the result of many factors including age, gender, weight, muscle and fat percentages, certain medical conditions as well as genetics.

I think exercise is the prime factor to increase the metabolic rate. Because the metabolic rate can be higher when exercising and so help to burn off those extra calories. Also with exercising you can gain more muscle that can help to burn more calories as it thought that muscle burns calories more quickly than fat. With those benefits you can make the body burn the calories more efficiently.

Eating a breakfast high in complex carbohydrates like whole grain cereal with skim milk and fruit will give you a long sustained energy source that keeps your metabolism at its optimum level until lunch. You can find more factors to increase the metabolic rate.

The most important thing to remember about doing exercise is always set up a safe exercises program and to not over. You can discuss it with your doctor if you need.