Is it Better to Exercise Before or After Meals?

When you exercise, your body relies on energy derived from the foods you consume in your daily diet. Eating before exercising is typically a vital way to provide your body with enough fuel to sustain physical activity. However, if you have diabetes or a related disorder called insulin resistance, eating after exercise can improve your body's ability to properly use the glucose in your bloodstream.

When you eat, your body takes the foods in your diet and breaks them down for various uses. One of the main products of this process is glucose, a form of simple sugar that acts as a primary source of energy and also helps your body grow and repair itself. Before you can use glucose, it must pass from your bloodstream to the interiors of your cells. To make this happen, your body produces a hormone called insulin, which tells your cells to give glucose the necessary access. Diabetics and people with insulin resistance either don't produce enough insulin for this task or don't respond properly to insulin's glucose-processing effects, the EndocrineWeb website explains.

If you eat before you exercise, you will supply your body with the raw materials needed to produce glucose. This is particularly important in the morning, when your body has usually used up the glucose supplied by foods you ate the day before. However, you need time to produce and process glucose, and if you start exercising too soon after eating, you won't add anything to your body's energy reserves. Typically, you should wait about three or four hours after eating a large meal, two or three hours after eating a small meal and an hour or so after eating a relatively small snack.

When you exercise, you temporarily increase your body's sensitivity to insulin, as well as your ability to transfer glucose from your bloodstream, according to a study reported in the "Journal of Applied Physiology." If you eat a meal in the aftermath of an exercise session, these changes in your body's responses to insulin and glucose can make it easier for you to properly process your food and use it for your short- or long-term energy requirements. If the food you eat has a relatively low carbohydrate content, this improved ability control your blood glucose can continue the day after exercise.

If you eat too much before you exercise, you can develop unpleasant effects that include sluggishness, stomach cramps and diarrhea. If you don't eat enough before exercise, you may not have enough energy to easily and comfortably complete your chosen activity. The increased insulin sensitivity associated with exercise fades gradually over time, and you must exercise regularly to see long-term improvements. If you have diabetes or insulin resistance, consult your doctor to learn more about the effects of exercise and the best time for you to eat your meals.