What is basal metabolic rate?

Even when we are sleeping or our body is at rest, there is energy required to keep the basic functioning of the body going. Basal metabolic rate, or BMR in short, is the amount of energy required to maintain optimum functioning of the body at rest.

This would include the energy required to keep the lungs, heart, kidneys, sexual organs, muscles, skin, brain, and liver functioning while the body is resting. It is measured in calories. An increase in basal metabolic rate can be expected to increase during exertion, stress, fear or illness. Similarly, BMR is expected to decrease as you grow older, resulting in the loss of any lean muscle mass.

The BMR is the most important factor that can help you decide how many calories you need to maintain to lose or gain weight. It depends on various genetic and environmental factors. Some of these include:

• Age: when we are young, our BMR is high. With age, the lean body mass lessens and there is a slowing down of BMR. After a person has reached 20 years of age, it drops about 2 percent, per decade.

• Genetics: The genetic factors can affect the BMR. Some people are born with higher BMR than others.

• Gender: Men usually have more muscle mass than women combined with a low percentage of body fat. This results in men having a higher BMR.

• Height & Weight: The person’s height and weight affects the BMR. A tall and thin person will have higher BMR than someone who is short. The heavier you weigh, the higher your BMR. This means the greater you body surface area, the higher your BMR.

• Percentage of body fat: People with lower body fat percentage will have higher BMR. Because of the fact that men have a lower percentage of body fat, men generally have a 10 to 15% faster BMR than women.

• Growth: Children and pregnant women will have higher BMR.

• Body Composition: If you have more lean body mass, you will have a higher BMR. On the contrary, if you have more fat tissues, your BMR will be lower.

• Body temperature and overall health: For every increase of 0.5C in internal temperature of the body, the BMR increases by about 7 percent. The chemical reactions in the body actually become faster at higher body temperatures. That is the reason during fever, the BMR increases.

• Glandular functioning: Thyroxin is a hormone that is produced by the thyroid gland. This hormone plays a key role as a BMR regulator, which hastens the rate of metabolic activity in the body. The more amount of thyroxin produced, the higher will be the BMR.

  In case too little thyroxin is produced, BMR may come down by 30 to 40% from normal level. The adrenaline of a person can also increase the BMR.

• Environmental Temperature: External temperature can affect BMR. For instance, in extremely cold temperatures, the body has to create extra heat to maintain the body’s internal temperature. This raises the BMR. Similarly, prolonged exposure to great heat may also raise the BMR.
• Fasting/Starvation: Dieting or starvation may result in an abrupt reduction of calorie intake. This lowers BMR. Sometimes weight loss diets can reduce BMR by as much as 20%.
• Thyroxin: This is the hormone for the thyroid, and is a component for regulating the BMR. The higher amount of thyroxin that is generated, the level of BMR also increases.
• Stress: There are various short-term factors which can affect the BMR. One of the most important factors would be stress. Stress raises the BMR.
• Exercise: By exercising regularly, you are aiding in the building of lean muscles and increasing your BMR.