Basal Metabolic Rate (BMR): The amount of an individual’s energy (calories) consumed by the body at complete rest or fasting without any exercises and required to do normal bodily functions such as respiration by lungs, food digestion by stomach, pumping blood by the heart, etc.
BMR expressed in units of energy per unit surface area per unit time.
If you are going to lose weight you should understand what is the meaning of basal metabolic rate because it is important to know how many calories you burn while resting. To lose weight you must consume fewer calories or burn more calories.
BMR is responsible for burning up to 70% of the total calories consumed, but this value varies due to many factors:
- Gender: Men have higher BMR than women because men tend to have larger bulk muscles and lower body fat percentages than women.
- Genetics: Some people are born with faster metabolism (high metabolic rate), And others with slower metabolism (low metabolic rate).
- Age: Children have higher BMR than adults due to the energy required for growth and when they become 20 years old BMR drops about 2 percent per ten years.
- Body Surface Area: Thin and tall persons tend to have higher BMRs than those who are shorter and overweight, So BMR is higher when body surface area is larger (Body surface area related to height and weight).
- Body Fat Percentage: People with a lower body fat percentage tend to have a higher BMR. So the lower the body fat percentage is, the higher BMR is.
- Dieting: BMR Starvation, fasting, or/and serious abrupt calorie-reduction can drastically decrease BMR by up to 30 percent. A restrictive low-calorie weight-loss diet may cut BMR by 20%.
- Body Temperature: The higher body temperature, The higher BMR because chemical reactions become very rapidly at higher temperatures. BMR increases by about 7 percent For each increase of 0.5C in a person’s internal body temperature.
- External Temperature: Both very cold and hot weather increase BMR. While short exposure to increased heat has little effect on the body’s metabolism.
- Glands: The thyroid gland is responsible for the production or secretion of a thyroxine hormone which considers a BMR regulator. BMR is higher if the thyroid gland is overactive, and lower if the thyroid gland is underactive. The adrenaline hormone may also increase BMR but to a lesser extent.
- Exercise: Doing exercises such as running, walking, etc increase BMR.
- Breast-feeding: BMR increases during breastfeeding, due to the energy required for synthesizing milk
- Malnutrition: BMR decreases during malnutrition
- Pregnancy: BMR increases during pregnancy
- Illness and Stress: Fever and high levels of stress may result in a BMR increase.