Calories are the units of measurement for the energy your body obtains from the nutrients in the food you consume. As a general rule, the more calories you consume, the more active you must be to maintain your weight. The more active you are, the more calories you will need. There is some evidence that individuals who eat fewer calories than they expend lose weight faster than those who eat a higher amount. This may be because those who eat less have to spend more time finding food that tastes good and is nutritious. Those who eat more can simply choose to eat whatever they want, which often includes high-calorie foods that were not part of their diet before starting the study. In order to keep your body using energy efficiently, you need to provide it with nutrients and absorb any vitamins that may help it function properly. This is especially important if you are overweight or obese. Being obese increases your risk for diseases such as heart disease, diabetes, and cancer. These conditions require extra care due to the additional stress they place on your body. For example, people who have diabetes cannot control their blood sugar levels as well as others who are not diagnosed with this condition. This means that they are at risk for experiencing complications such as blindness, kidney failure, and nerve damage. Your body uses calories whether you are conscious of it or not.