The reason is that when we are asleep, a series of complex biochemical reactions are underway to keep the organization alive, breathing and blood circulation to the organs. Thus, the calories are burned throughout the year by several processes and BMR body could be tasked to burn up 70% of total calories. This is the only factor that determines the number of calories you need to maintain, gain or weight loss.
BMR can vary depending on several factors including:
• Genetics: the rate of metabolism may be faster or slower depending on genetic factors.
• Sex: men tend to have more muscle and less body fat. That makes BMR higher in men than women.
• Age: BMR rise with age. It reduced by 2% every ten years after reaching 20 years.
• Body weight: BMR depends on body weight. If you are heavy, you have a higher BMR. For example, the BMR of obese women was 25% higher than for women who were lean and thin.
Similarly, the metabolic rate can vary depending on many factors such as body surface area, the percentage of body fat, etc. In fact, the lowest percentage of fat you have in your body, the higher your metabolic rate. This is the reason why men are generally from 10 to 15% faster than the metabolic rate of women. Diet, body temperature or health conditions, environmental temperature, glandular functions, and so are other factors that can influence the metabolic rate of a person.
Although it is generally believed that men are higher than women's metabolic rate, and the entire body weight, men usually have less fat and more lean body mass, it there might be other causes hormonal result in the difference. Differences in sensitivity and hormones like leptin, thyroid, insulin and catecholamines are thought to be responsible for the difference in the BMR between men and women.
With all factors taken into account, women usually run about 3% less than men BMR. Even hormones like estrogen and progesterone may affect the BMR.
Thus, while BMR may vary and depend on many factors, men typically have higher metabolic rates than women because of less fat and more muscle and lean body mass in their bodies.