Metabolism is regulated by various hormones and enzymes found throughout the body. Hormones such as insulin, glucagon, growth hormone, and thyroid hormones control the rate of various metabolic pathways. Enzymes also act as regulators of metabolic pathways, controlling the rate of reactions and allowing for specific reactions to occur. Additionally, dietary factors can also affect metabolic pathways and the rate of metabolism. For example, an increase in dietary carbohydrate can increase the activity of certain enzymes involved in the breakdown of carbohydrates.