I just wanted to share with you the known variables to influence your basal metabolic rate according to the American Council on Exercise.
- Genetics. Some people have a naturally high metabolism and others have naturally slow metabolisms.
- Gender. Men have more testosterone and usually more lean muscle mass and less fat mass than women so they have a higher metabolism.
- Age. BMR is greater in childhood than in adulthood. After age 20, BMR is estimated to drop about 2 percent to 3 percent each decade. This is not a huge decline as you can see so stop using it as your excuse.
- Weight. The more an individual weighs, the higher his or her BMR will be. For example, if two people are the same height but one is heavier, the heavier one will have the higher BMR.
- Height. Taller people typically have greater body surface area and more lean body mass.
- Body-fat Percentage. If all other things are equal, people with a higher body-fat percentage have a lower BMR than those with a lower-body fat percentage.
- Diet. Starvation or serious abrupt calorie-reduction can dramatically reduce BMR by up to 30 percent. Likewise, restrictive, low-calorie weight-loss diets may cause BMR to drop by as much as 20 percent. This is why I tell you to eat 5-6 small meals a day!
- Body Temperature/Health. For every increase of 0.5 degrees C in internal temperature of the body, BMR increases by about 7 percent. The chemical reactions in the body actually occur more quickly at higher temperatures (remember high school chemistry?) Therefore, a person with a fever of 42 degrees C (about 4 degrees C above normal) would have an increase of about 50 percent in BMR. Maybe why we lose weight when we are sick?
- External temperature. Temperature outside the body also affects basal metabolic rate. Exposure to cold temperature causes an increase in the BMR, as the body tries to create the extra heat needed to maintain its internal temperature. A short exposure to hot temperature has little effect on the body’s metabolism because of compensatory increases in heat loss. However, prolonged exposure to heat can raise BMR.
- Glands. Thyroxin (produced by the thyroid gland) is a key BMR regulator that speeds up the body’s metabolic activity. The more thyroxin produced, the higher the BMR. If too much thyroxin is produced (a condition known as thyrotoxicosis), BMR can actually double. If too little thyroxin is produced (myxoedema), BMR may shrink to 30 percent to 40 percent of normal. Like thyroxin, adrenaline also increases the BMR, but to a lesser extent.
- Exercise. Physical exercise not only influences body weight by burning calories, it also helps raise BMR by building extra muscle (this is why everyone should do resistance training!) The greater the exercise intensity, the longer it takes the body to recover, which results in a longer and higher excess post-exercise oxygen consumption (EPOC). When your body is in a state of EPOC, you are burning a lot of calories while you recover and is one of the most proven methods to shed body fat. Not everyone is ready to train at a high intensity and should build up to do so with the proper progression and guidance of a trainer, preferably me!
The take home message is that besides what you are dealt with by genetics and any other variables that fall under that umbrella; you have some control over your metabolism through proper diet and exercise.