Resting Metabolic Rate Assessment
RMR explains how many calories are required by your body to perform the most basic functions (to keep itself alive) while resting. These essential functions are:
Sustaining the function of vital organs
RMR does not account for calories burned to support physical activity. Anything that we do through a day requires energy (calories) to be burned in addition to those used to support resting metabolic rate.
Factors that affect RMR:
Many factors can significantly impact your RMR:
People are born with faster metabolisms, while others naturally have slower metabolisms.
Men, on average, have a greater muscle mass and a lower body-fat percentage than women, they generally have a higher RMR.
RMR is greater in childhood than in adulthood. After age 20, RMR is estimated to drop about 2 to 3 percent each decade.
The more an individual weighs, the higher his or her RMR will be. For example, the metabolic rate of very overweight individuals is generally higher than that of their normal-weight counterparts.
Taller people typically have greater body surface area and more lean body mass (LBM).
Body Fat %
Fat Percentage- all other things being equal, people with a higher body-fat percentage have a lower RMR than those with a lower-body fat percentage.
Starvation or serious abrupt calorie-reduction can dramatically reduce RMR by up to 30 percent. Likewise, restrictive, low-calorie weight-loss diets may cause RMR to drop by as much as 20 percent.
For every increase of 0.5 degrees C in internal temperature of the body, RMR increases by about 7 percent. The chemical reactions in the body actually occur more quickly at higher temperatures. 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 RMR.
Temperature outside the body also affects RMR. Exposure to cold temperature causes an increase in the RMR, 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 RMR.
Thyroxin (produced by the thyroid gland) is a key RMR regulator that speeds up the body’s metabolic activity. The more thyroxin produced, the higher the RMR. If too much thyroxin is produced (a condition known as thyrotoxicosis), RMR can actually double. If too little thyroxin is produced (myxoedema), RMR may shrink to 30 percent to 40 percent of normal. Like thyroxin, adrenaline also increases the RMR, but to a lesser extent.
Physical exercise not only influences body weight by burning calories, it also helps raise RMR by building extra muscle. 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).