You might only pay attention to how many calories you burn when you exercise--but your body is constantly expending energy by burning calories, even when you sleep! When you understand the factors that influence your resting metabolic rate, such as muscle mass, you can learn to adjust your eating habits based on your level of exercise, your age, and your body's energy needs.

What Is Resting Metabolic Rate?

Your resting metabolic rate--also called basal metabolic rate--corresponds to the number of calories you'd burn if you stayed sedentary all day. In other words, it's the number of calories you naturally burn even without being active. This happens because your body needs to expend some energy for basic maintenance functions, such as breathing and keeping your heart beating.

The Mayo Clinic reports that metabolism adjusts to your individual needs and is not easy to change. However, when you don't eat often enough by skipping meals or attempting starvation diets, your body may attempt to conserve calories. Ironically, this can make it harder to lose weight. The Mayo Clinic also notes that your resting metabolic rate decreases as you age. This may mean that you need to be more active as an older person to burn the same number of calories that you did when you were younger.

The Importance of Muscle Mass

Your resting metabolic rate is affected by your body composition and muscle mass. This is because when compared with fat, muscle requires more energy to function. For example, one reason your basal metabolic rate may decrease with age is that when you get older, you're likely to lose muscle and gain fat.

However, you can have a different metabolic rate than someone of the same age and weight if you have more muscle mass. A higher muscle mass corresponds with an increase in metabolic rate, so it's important to stay fit. Engaging in strength training as you age may help you avoid weight gain. But remember, building muscle isn't a magical metabolism solution. It's important to eat a healthy diet and engage in aerobic exercise, like walking, too.

Increasing the Burn, Decreasing the Calories

When it comes to your body's energy expenditure, your resting metabolic rate isn't the only consideration. The BCC reports that your body's total energy needs depend on a combination of your resting metabolic rate and the energy you use for physical activity and moving around during the day.

It's not easy to change your metabolism. If you want to lose a small amount of weight, your time will be better spent on starting to exercise regularly. Even a small amount of exercise, such as a daily walk, may make a difference over time. The American Heart Association recommends that all adults aim for at least 30 minutes of exercise, five days per week. That may sound like a lot, but remember that you can break it into smaller sessions. Two fifteen-minute walks--perhaps one on your lunch break and one after work--would do the trick.

The other half of the equation is what you eat. If you take in more calories than your body needs and don't exercise them off, you'll gain weight. By controlling your body's energy expenditure through regular physical activity and not overeating, you can lose weight and maintain it over the long-term.

HealthAhead Hint: Making It Stick

The best way to burn more calories is to exercise more often. Unfortunately, there are no easy short cuts. The number of calories you'll be able to burn through physical activity will vary depending on your age, gender, and body size. However, regardless of these individual factors, you may increase muscle and decrease fat by becoming more active. This might have a slight influence on your metabolic rate, but more importantly, you may already be well on your way to better health.