One of the main functions of metabolism is to convert the food we eat into energy. According to Dr. Robert Keith, professor of nutrition and food science at Auburn University, our metabolism can decline by as much as 20 percent to 25 percent between the ages of 22 to 75 years old. He suggests preserving and adding muscle mass to offset this decline.

Drink Water
There are many benefits to staying hydrated, such as regulating body temperature, transporting nutrients, disposing of waste products, protecting vital organs and supporting life. Your metabolism will speed up by approximately 30 percent when drinking two cups of cold water on an empty stomach, according to the "Journal of Clinical Endocrinology & Metabolism."

Physical Activity and Exercise
To increase your metabolism you need to add more muscle. Exercise will not only give you more energy and add muscle mass, it will help you create a negative caloric balance---meaning you will be burning more calories than you are taking in. Incorporate strength training and cardio vascular training into your weekly routine to shed those extra pounds and increase your muscle mass. Depending on the amount of exercise you are doing, your weight and the intensity of your exercise you can burn approximately 70-1,000 calories daily, according to the American Council on Exercise, by bowling, running, jogging or swimming for 60 minutes.

Eat Small, Frequent Meals
By eating small meals, five to six times per day, according to "Oxygen" magazine, you can satisfy your hunger and keep your metabolism burning strong all day. Developing healthy eating habits as a lifestyle change, combining lean protein with complex carbohydrates and watching your portion sizes can help keep your metabolism on track. Dr. David C. Nieman, director of the Human Performance Laboratory at Appalachian State University, suggests that gaining weight by eating too much can cause your metabolism to increase to combat the weight gain and eating too little can cause your metabolism to decrease in order to conserve calories, not allowing you to lose as much weight as you expected. Our metabolism strives to maintain a sense of balance---adjusting levels as needed based on our lifestyle.