Did you know that your basal metabolic rate, or BMR, is the minimum calorific requirement needed to sustain life in a resting individual? So obviously with weight loss and dieting in mind, your Basal Metabolic rate could prove to be a key factor.
Your BMR can also be looked at as being the amount of energy (measured in calories) expended by the body to remain in bed asleep all day! BMR can be responsible for burning up to 70% of the total calories expended, but this figure varies due to different factors (see below).
Calories are burned by bodily processes such as respiration, the pumping of blood around the body and maintenance of body temperature. Obviously the body will burn more calories on top of those burned due to BMR.
As we grow older, our BMR will steadily decrease. In youth, BMR is higher, and as we age we have less lean body mass - slowing the BMR. The more lean tissue on the body, the higher the BMR, the more fatty body tissue, the lower the BMR. (This does mean that an individual can raise their basal metabolic rate by undertaking regular exercise). A person's height is also a factor, a tall thin person will have a higher BMR than a shorter, fatter person. BMR will increase in pregnant women.
Short Term Factors Affecting BMR
Illnesses such as a fever, high levels of stress hormones in the body and either an increase or decrease in the environmental temperature will result in an increase in BMR. Fasting, starving or malnutrition all result in a lowering of BMR. This lowering of BMR can be one side effect of following a diet and nothing else. Solely dieting , i.e. reducing the amount of calories the body takes on, will not be as affective as dieting and increased exercise. The negative effect of dieting on BMR can be offset with a positive effect from increased exercise.
Thyroxin - The Body's BMR Controller
Thyroxin is a hormone that is produced by the thyroid - a small gland in the neck, just under the Adam's apple - and is a key BMR-regulator which controls the metabolic activity within the body.
When the thyroid is not working properly (called thyroid disorder), it can affect your body weight, energy level, muscle strength, skin health, menstrual cycle (periods), memory, heart rate, and cholesterol level.
An excess of thyroxin circulating in the body, (a condition known as thyrotoxicosis) can cause the BMR to double. If too little thyroxin is produced (a condition known as myxoedema) BMR may shrink to 30-40 percent of normal.