This is a topic that can get very “wordy” very quickly, but no worries, it will be simplified and formatted so it can be understood.
When one thinks of metabolic rate, metabolism of course comes to mind. Metabolism is the process in which the body breaks down and utilizes calories for energy. Metabolic rate can be looked at in another way however. How much energy does the body need to just function? When you are laying in bed doing absolutely nothing, the body is still functioning and requiring energy just to keep you alive. Let us say you were in a rest state for 24 hours. The energy used by the body during this time is called basal metabolic rate, or BMR. Variables that are looked at when figuring up one’s BMR is height, gender, and age.
Out of the three, age has shown to have adverse effects on one’s BMR. The reason for this is based around muscle mass. As one loses weight, the person’s BMR decreases because they require less calories. On the contrary, if a person gains dense, lean muscle mass, their BMR will increase because more calories are required from the body to function. If one was to gain fat, the BMR would decrease. In other words, muscle requires more calories than fat when talking about BMR.
With all of that being noted, as a person ages, they lose muscle mass.
See where this is going?
As muscle mass goes away, BMR is affected is decreases significantly. Studies show that after the age of 30, muscle mass can decline five to 10 percent each decade after. These are high drops in muscle mass in the long run.
This hits on another important topic; nutrition. As a person ages the importance of proper nutrition goes up more and more. This is even more the case if you are a fitness person or bodybuilder, where muscle growth is the objective.
Bodybuilders will of course have a higher BMR due to the higher muscle mass, but no one is immune to time. And in this case, time hinders muscle growth, so keeping protein levels up is important for feeding those muscles.
The beauty of building muscles is the chess game between a person and their body. As this article hits on, the body is always changing literally with each moment. Keeping one step ahead is a difficult task, so instead of focusing on being ignorantly proactive, people need to focus on being cleverly reactive with their bodies.
Take what it gives you and respond accordingly and respectfully.