The basal metabolic rate decreases almost linearly with age. The volume of skeletal musculature decreases and the percentage of fat tissue increases with age. It is shown that the decrease in muscle mass relative to total body may be wholly responsible for the age-related decreases in basal metabolic rate.
What is a good BMR?
Your BMR score is a number which refers to how many calories you burn at rest. Most people's BMR is between 1000 2000. This means that they need to take in between 1000 2000 calories each day to fuel their basic functions while in a resting state.