What factors affect Resting Metabolic Rate?

Many factors affect your resting metabolic rate; some you can control while others you can't.

Some factors you can't control:

Age

Resting metabolic rate naturally decreases with age at approximately 2% per decade after peak growth.

Genetics 

Scientists have identified many genes that are related to obesity that can affect resting metabolic rate. Luckily, most researchers believe your lifestyle and environment can overcome the contribution of your genetics.

Epigenetics of Your Ancestors

Epigenetic factors include gene expression influenced by the environment and lifestyle of your parents and grandparents.

Some controllable factors:

Lean Body Mass

Increasing lean body mass is the most effective and safe way to increase resting metabolic rate. Maintaining healthy lean body mass can help combat age-related metabolic rate losses. Lean body mass itself is a result of calories, nutrition, and exercise.

Research has shown even a small gain of 2 to 4 pounds of muscle mass can provide a 7 -8% boost in metabolism

Sleep

Lack of sleep can influence how your body prioritizes energy, resources, and stress hormone balance — all of which can negatively impact your resting metabolic rate.

Low Caloric Intake

Sustained very low caloric intake can suppress resting metabolic rate by up to 20%. This is because very low caloric intake can cause elevated levels of the stress hormone cortisol which can suppress thyroid-stimulating hormone production that regulates metabolism. Very low caloric intake also causes a reduction in muscle mass which in turn reduces metabolic rate.

Stimulants

Stimulants like caffeine and capsaicin can temporarily boost metabolic rates.

Cold therapy

Also known as "cold thermogenesis", subjecting your body to brief periods of cold, usually with cold water, can boost metabolism through a variety of pathways.