Calories are the energy in food. Your body has a constant demand for energy and uses the calories from food to keep functioning. Energy from calories fuels your every action, from fidgeting to marathon running.
Carbohydrates, fats and proteins are the types of nutrients that contain calories and are the main energy sources for your body. Regardless of where they come from, the calories you eat are either converted to physical energy or stored within your body as fat.
These stored calories will remain in your body as fat unless you use them up, either by reducing calorie intake so that your body must draw on reserves for energy, or by increasing physical activity so that you burn more calories.
Tipping the scale
Your weight is a balancing act, but the equation is simple: If you eat more calories than you burn, you gain weight. And if you eat fewer calories and burn more calories through physical activity, you lose weight.
In general, if you cut 500 to 1,000 calories a day from your typical diet, you'll lose about 1 pound (0.5 kilogram) a week.
It sounds simple. However, it's more complex because when you lose weight, you usually lose a combination of fat, lean tissue and water. Also, because of changes that occur in the body as a result of weight loss, you may need to decrease calories further to continue weight loss.
