Metabolism describes all the chemical reactions in a cell. Because our cells always lose energy as heat, they require constant energy input to continue fueling their reactions. So the familiar definition of metabolism—how fast a person burns calories in food—relates to the rate at which cellular reactions are occurring. What can you do to make your cells use the energy in food more quickly?
Exercise speeds up the body’s energy metabolism in several ways. Immediately after exercise, cells work to rebuild ATP and other energy reserves, so caloric demands are high. Also, body temperature remains elevated for hours after exercise, speeding chemical reactions and contributing to increased metabolism. Regular exercise also increases the size of muscle cells, which require more energy than fat cells even when at rest.
Caffeine may also accelerate metabolism. Although caffeine contains zero calories, many people can attest to the “energy boost” that it provides. Caffeine increases the release of fatty acids into the blood and raises the heart rate, giving cells quick access to energy reserves. However, studies have shown that getting too little sleep (a side effect of excess caffeine) disturbs normal metabolism. Finally, cellular metabolism slows when you go for a few hours without food. One way to keep your metabolism high is therefore to maintain your blood sugar level by eating multiple small, healthy meals throughout the day.