When a person has diabetes, their metabolism is affected because insulin levels decrease, preventing the body from storing energy from food for later use. This is particularly the case for type 1 diabetes, where the immune system attacks the cells responsible for producing insulin in the pancreas.

Metabolism is the process by which the body generates energy from the food and drink consumed. After a meal, carbohydrates, proteins, and fats are broken down to release energy that fuels biological processes in the body. Energy is expended in three ways: resting energy expenditure, diet-induced energy expenditure, and activity-induced energy expenditure.

People with slower metabolisms tend to have a lower basal metabolic rate (BMR), which is the energy required for essential bodily functions at rest, such as breathing. Factors that can influence BMR include muscle mass, bone size and density, body fat, age, and genetics.