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What biological factors influence a person's metabolic rate?

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Color-enhanced electron micrograph showing yellow mitochondria and blue endoplasmic reticulum within magenta-stained hepatocyte liver cells at high magnification. — Metabolism Electron micrograph of hepatocyte cells showing mitochondria (yellow). The primary function of mitochondria is to generate large quantities of energy in the form of ATP, which captures chemical energy from the metabolic breakdown of food molecules.

Biological factors influencing a person's metabolic rate include age, body composition, and hormonal function. As individuals age, lean body mass typically decreases, leading to a slower metabolic rate. Hormones, particularly those from the thyroid gland, play a crucial role in regulating metabolism and oxygen consumption. Thyroid hormones increase metabolic rate, and their deficiency can disrupt growth and maturation.12

Furthermore, the amount of lean body mass, which includes muscles and cellular tissues, directly impacts metabolism. A decrease in lean body mass, often due to aging and disuse, is accompanied by a reduction in overall metabolic activity. The body's ability to adjust to environmental changes and recover from physiological stress also diminishes with age, affecting metabolic regulation.13