In the last blog we discussed about Basic metabolic rate (BMR), understanding how it affects your body is a vital step in weight management. In this blog we look at the factors that affect BMR.
Factors affecting BMR:
Age– During periods of growth,the BMR increases fore.g. From infancy to childhood there is extensive increase in BMR . The tissues in the body are growing and expanding rapidly which is why children or adolescents are constantly hungry
In adult life, it is opposite. Since majority of the growth is over, BMR starts to decline as we age. BMR decreases by 2-3% per decade throughout adult life, probably due to decrease in skeletal muscle mass
Gender– Males have a 10-15% higher metabolic rate than females due to greaterskeletal muscle mass.
Body size– A person smaller in size has a larger surface area per unit volume. Thus, the rate of heat loss is high and hence a higher BMR
Sleep– Sleep reduces BMR by 10 -15% due to a reduction in nervous system and muscle activity. The body systems slow down during sleep thus reducing rate of burning calories. Hence, it is advisable to eat early meals (i.e. latest by 8) or atleast 2 hours before going to sleep.
- Thyroxine stimulates oxidation and increases heat production within cells (maximal thyroxine secretion is associated with a rise in metabolic rate by 50 ‐ 100%)
- Catecholamines increase BMR
- Testosterone increases BMR by 10 ‐ 15% (mainly due to its anabolic effect on skeletal muscle mass)
- Growth hormone increases BMR by 15 ‐ 20% due to direct effect on cellular metabolism
Pregnancy and lactation- BMR increases by about 15% during the later stages of pregnancy to support the growth of the fetus and related tissues
Nutritional status– BMR rises by 4‐ 30% for 3 – 12 hours after a meal (thermogenic effect of food). However, during starvation or fasting the BMR slows down 20 ‐ 30% due to a reduction in tissue metabolism. This is a natural adaptation by the body to conserve more energy when there is a deficit. That is why fasting or starvation is, in fact, detrimental to weight loss because the body goes into a conservation mode and whatever little is eaten quickly goes for storage to save enough for the next period of fasting.
The principle of small frequent meals is based on the premise that eating stimulates the metabolism and thereby helps in burning more calories. Of course, it is important to choose the right type and amount of foods eaten.
Climate – BMR is 10% ‐ 20% higher for individuals living in arctic regions compared to the tropics. In order to acclimatize, more energy is used up in maintaining body temperature.
Pathology -BMR increases by ~14% per degree of fever. Trauma, burns and malignancy also increase BMR
While the BMR remains a major component of energy expenditure , diet and physical activity are yet the vital factors that can change the game. Also, remember that the Muscle mass or fat free mass can be increased with exercise and proper diet which in turn is the most vital tool to increase BMR.
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