Metabolic Rate is the rate at which the body burns up calories. The metabolic rate is influenced by numerous factors, including age, gender, muscle-to-fat ratio, amount of physical activity and hormone function. . A body that consumes 2500 calories a day, and burns 2500 calories a day will stay at the same weight. A body consuming 2500 calories daily but burning just 2000 calories will gain weight at the rate of about 1lb a week.
You can do quite a lot to speed up your metabolism – the secret of burning calories lies in knowing what determines your metabolic rate and what you can do to influence it.

You can boost your rate of burning calories using some, or all, of the following tactics:

Exercise and Build Muscle Mass.  Increase the rate of burning of calories by taking on additional physical activities like aerobic exercises, walking, swimming, cycling or running. You should combine this activity schedule with some muscle strengthening exercises.  During moderately vigorous physical activity, you elevate your metabolic rate by a factor of 10 or more, expending hundreds of extra calories.
The more vigorously you exercise, the more calories you use per minute.

Increase Movement in Daily Lifestyle. The more you move, the more you burn. You can actually make a significant addition to the number of calories you burn each day by relatively minor changes in lifestyle. This can be as simple as taking the stairs instead of the elevator; park a distance from the mall or office; window-shop with your best friend rather than sit over coffee; walk the dog instead of just let him out; do a little gardening or clean house while you talk on the phone.
Make friends with people who are equally interested in physical activity. Having a friend while doing physical activities can keep you motivated.

Diet
- Avoiding alcohol, eating lots of fruits and vegetables, increasing fiber in the diet combined with adequate and regular physical exercises yield far better results than fad diets and dietary supplements.
- Eat small, regular meals. Eating smal meals or snacks at regularly timed intervals seems to result in a slightly higher metabolism than eating in an irregular fashion, at least in overweight women. Eating in this way also discourages hunger, so you are less likely to feel deprived and overindulge. If you are changing your eating habits to eat more frequently, be sure you are not adding calories.
- Consume protein. It takes more calories to digest protein, and a high protein intake may reduce hunger. Replace high carbohydrate, empty calorie foods with proteins such as eggs, beans, soy products, fish, nonfat dairy products and lean meats

Sleeping habits.  You might think that since you use more calories awake than asleep, getting less sleep would help you to lose weight. Research shows that this is not the case. According to researchers at the University of Chicago, women who got less than four hours of sleep per night had a slower metabolism than those who slept for a full eight hours.

Eat breakfast. There is a reason for the cliche about breakfast being the most important meal of the day. That is because after fasting all night, your metabolism is at its lowest point in the morning. You need to stoke the metabolic fires with a good breakfast that contains both carbohydrates and protein. Breakfast first thing keeps this from happening and gives you energy to start the day.

Remember that excess body fat did not happen overnight and cannot evaporate in a day either.