Metabolism: Truths and Myths

We hear a lot about metabolism and often blame our “slow metabolism” for our inability to keep our weight under control. But what is metabolism, exactly? And is there anything we can do to change our metabolic rate?

Metabolism basically refers to all the chemical processes that take place in the body in order to sustain life – allowing you to breathe, pump blood, keep your brain functioning and extract energy from your food.

When you hear the term metabolic rate more accurately called basal (or resting) metabolic rate that refers to the number of calories your body at rest uses each day, just to keep all your vital organs functioning.

You burn additional calories through your daily activities and formal exercise, but by far, the majority of the calories that you burn each day are your basal calories.

The number of calories that you burn every day is directly related to your body composition. Think of your body as divided into two compartments. In one compartment is all the body fat; in the other compartment is everything that isn’t fat (e.g., bone, fluid, tissue, muscle)–that’s the fat-free compartment. The size of your fat-free compartment determines your metabolic rate, with every pound of fat-free mass burning about 14 calories per day.

If you weigh 150 pounds and 50 pounds of you is fat and 100 pounds is fat-free, then you would burn about 1,400 calories per day at rest. If you don’t get much activity, you won’t burn much more than this throughout the day. But if you weigh 150 pounds and 25 pounds of you is fat, and 125 pounds of you is fat free, then you burn 1,750 calories per day at rest. And if you get some regular exercise and burn a few hundred calories more per day, your total calorie burn for the day might be 2,000 calories!

Since the fat-free compartment contains muscle tissue, one of the best things you can do to boost your metabolic rate is to strength-train to increase your muscle mass. If you build up 10 pounds of lean body mass, that’s another 140 extra calories that you burn per day–not to mention the calories that you burn through exercise.

Here are a few truths and myths about metabolism:

Myth: Aging slows your metabolism.

Truth: People do tend to put on weight as they get older, but it isn’t inevitable. People have a tendency to exercise less, or less vigorously, as they age–and that means fewer calories burned per day. As activity levels and intensity go down, loss of muscle mass can occur. This then shrinks the body’s fat free compartment and leads to a lower metabolic rate. Cardiovascular exercise will burn calories, and resistance training to preserve or build up muscle are great defenses against age-related weight gain.

Myth: You’re stuck with the metabolism you have, and you can’t change it.

Truth: We all seem to know people who can “eat whatever they want and never gain weight” or those who “just look at food and put on 10 pounds.” But lifestyle plays a big part in determining the calories you burn per day. While it may appear that there are people who eat all the time and never seem to gain, chances are they make healthy, relatively low-calorie selections naturally. And many of these people burn more calories through what is called Non-Exercise Activity Thermogenesis (NEAT)–basically, they move around a lot during the day. They might fidget more, get up from their desks frequently during the day to stretch, or walk down the hall to talk to a colleague instead of emailing. 

The more muscle you have, the higher your metabolism, the faster you burn calories. Eating plenty of protein daily is essential to maintaining your muscle mass for good health, energy and effective weight management.