Metabolism is defined as the number of calories the body needs while at rest. In other words, the body needs a certain number of calories just to sustain bodily functions, like breathing and heartbeat. This number is usually referred to as the basal metabolic rate (BMR).
Because your thyroid controls your metabolism through the secretion of hormones, it is these hormones (and your physical fitness level) that control how fast (or slow) food is converted into energy. If you are having trouble losing weight, it could be that your thyroid is not functioning normally. Your doctor can check it with a simple blood test.
One fact we know is that a pound of fat burns about 10 calories while a pound of muscle burns almost 30 calories over the same given period of time. So it makes sense that the more muscle you have, the more calories you’ll burn just to sustain the additional muscle. Because of this fact, gaining lean muscle mass is one way to increase your metabolic rate.
Another way is through physical exercise; exercise triggers an increase in metabolism that can last for several hours after finishing your workout. By incorporating weight training into your routines, not only do you increase your metabolism in the short term, but also permanently through the building of lean muscle mass. A win/win situation!
But how do you know if your metabolism is low, normal, or high? First you have to know your BMR – the number of calories your body needs to function while at rest. If the number you consume is higher, but you are not gaining weight, then you have a high metabolism. To calculate your BMR, use these formulas:
• women: 655 + (4.3 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years);
• men: 66 + (6.3 x weight in pounds) + (12.9 x height in inches) – (6.8 x age in years).
Note the formulas are based on a normal adult body. If you are extremely muscular or very obese, then your resulting figures will be underestimated or overestimated, respectively.
For example, let’s use a 30-year old, 5 ft. 10 in. tall male weighing 170 pounds. Plugging the numbers into the formula 66 + (6.3 x 170) + (12.9 x 72) – (6.8 x 30), we come out with 66 + (1071) + (928.8) – (204) = 1,861.80 calories per day to maintain his current weight. If our study is eating significantly more calories and not gaining weight, then he has a high metabolism. Because he burns calories at a higher rate, it will be easier for him to lose weight just from cutting calories.
While your thyroid basically controls your metabolism, you can help increase its functioning through healthy eating, regular exercise, and building of lean muscle mass.