Basal Metabolic Rate (BMR) is the amount of daily energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans).
Even when your body is at rest, it needs energy to perform various functions such as breathing, keeping your heart beating and maintaining your body temperature.
This is the minimum amount of calories you body needs to burn to stay alive and is typically around 70% of the total amount of calories you need each day.
Factors in Determining the Basal Metabolic Rate:
BMR is the largest factor in determining overall metabolic rate and how many calories you need to maintain, lose or gain weight. BMR is determined by a combination of genetic and environmental factors.
1. Genetics. There are people born with faster metabolism and some with slower.
2. Gender. Men have greater muscle mass and lower body fat percentage than women. This means men have greater BMS.
3. Age. BMS reduces with age. After 20 years, there is a 2 percent drop per decade of a person’s BMS.
4. Weight. Heavier people needs more calories, thus they have more BMS.
5. Body Surface Area. The greater your Body Surface Area factor, the higher your BMR. Tall, thin people have higher BMRs.
6. Body Fat Percentage. The lower body fat percentage, the higher the BMR. It is the reason why male body generally have 10-15% faster BMR than women.
7. Diet. Starvation or serious abrupt calorie-reduction can dramatically reduce BMR by up to 30 percent.Restrictive low-calorie weight loss diets may cause your BMR to drop as much as 20%.
8. Body Temperature/Health. The chemical reactions in the body actually occur more quickly at higher temperatures. So a patient with a fever of 42C (about 4C above normal) would have an increase of about 50 percent in BMR.
9. External temperature. Temperature outside the body affects the basal metabolic rate. When it is colder, the body needs more energy to maintain the internal temperature. This increases the metabolic rate of a person. A short exposure to hot temperature has little effect on the body’s metabolism as it is compensated mainly by increased heat loss. But prolonged exposure to heat can raise BMR.
10. Glands. Thyroxin (produced by the thyroid gland) is a key BMR-regulator which speeds up the metabolic activity of the body. 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 30-40 percent of normal. Like thyroxin, adrenaline also increases the BMR but to a lesser extent.
11. Exercise. Physical exercise not only influences body weight by burning calories, it also helps raise your BMR by building extra lean tissue. (Lean tissue is more metabolically demanding than fat tissue.) So you burn more calories even when sleeping.
Here’s a calculation, called the Harris-Benedict formula, that you can use to roughly figure your BMR:
For Men:
BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) – (6.8 X age in years)
For Women:
BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) – (4.7 X age in years)
Basal Metabolic Rate and Weight Loss
When it comes to losing weight, your basal metabolic rate is important. In simple terms, the higher it is the more you can eat. Any excess calories that are not needed to perform your daily functions will be stored as fat.
But, all calories are not created equal and since it takes energy to actually digest the food some foods can be eaten in larger amounts than others. For example, a steak will take a lot more calories to break down than a Twinkie.
Knowing about own basal metabolic rate can help a person lose weight faster and stay slimmer. Increasing it will burn more calories overall and thus lose more weight (or be able to maintain and eat more calories).
One way to increase metabolism is to build more muscle and get rid of fats. It takes 50 calories each day to “power” one pound of muscle but only 2 calories for the same amount of fat.
Needless to say, replacing 10 pounds of fat with 10 pounds of muscle your whole eating plan would take on a whole new look!
In losing weight, simply eat less calories than what you burn, so knowing your BMR is important. Remember, BMR is the amount of calories needed while at rest, so unless you lay on the couch all day you will actually need to eat a lot more calories.
So, in addition to your BMR, you need to figure out the calorie expenditures of your other activities including exercise and add those onto the BMR value.
