According to the NIH, the term metabolism refers to the processes in the body that use energy, but the word is most used when we talk about weight. When a person says they have a fast/slow metabolism they are typically referring to their ability to lose weight or maintain a normal weight. Generally, most people can increase/decrease the rate at which they burn calories but many don’t know how to or that biological sex, daily habits, and health status can affect their metabolism.
The term metabolism can refer to any number of chemical processes that occur within the body, but in terms of weight loss what most people are interested in is BMR. BMR is how much energy a person uses every day to stay alive, and according to the National Strength and Conditioning Association, it accounts for around 65-70% of total caloric expenditure. There are many online calculators that attempt to estimate your BMR but they don’t take into account muscle to fat ratio, for a more accurate figure talk with a specialist for a calorimeter test to determine your BMR.