Over the past few months, I have noticed an interesting pattern. Many people believe that in order to lose weight, eating before or after exercise will "undo" all of their efforts during a work out. They therefore choose not to eat something after exercise. This is a false notion, and can actually have a negative impact on your ability to lose weight.
Prior to a workout, the carbohydrates (fruit, vegetables, grains) that we've eaten are broken down into glucose, and stored as glycogen in the muscles and liver. Fat and protein are stored too, but cannot be mobilized quick enough to be used by exercising muscles, so the body relies predominantly on carbohydrates. Muscle glycogen is the preferred energy because it can be accessed the fastest; if depleted, the body will turn to the stores of glycogen in the liver, which we want to avoid.
While working out, the amount of stored energy begins to deplete, just as a gas tank creeps steadily from full to empty during a road trip. And if the 'empty light' goes on during a road trip, it's very important to get to a gas station and refill. If you have ever started to feel dizzy, shaky, or light headed during or after a workout, this is your body's "empty light," and is the physiological response to the fact that your muscles are depleted of energy; you are running on empty.
Unfortunately, this will very likely lead to a binge on starchy carbohydrates immediately after you finish working out....not such a great scenario for weight loss. Workouts such as cycling are such high intensity that people often deplete their glycogen stores, leading right to a binge on quick and convenient carbohydrates. A prime example is the person working hard at Spin class week in and week out, who somehow does not lose a pound. They are eating back more energy than they expended through exercise, and therefore do not lose any weight.
The best way to prevent this is to plan ahead: eat a light meal or snack about one hour before your workout that consists of protein and carbohydrates to prepare your body for exercise. Examples include a turkey sandwich, a salad with grilled chicken, or an omelet with vegetables.
Post workout nutrition is also critical, for exercisers at any level. Eating a snack of 25-50 grams carbohydrates and 6-20 grams protein within one hour of working out is extremely beneficial, and, contrary to popular belief, does NOT undo all of your hard work. Rather, post exercise is a unique window of time in which the insulin response in your body causes an increase in the uptake of glucose into the muscles. Picture your muscles as tiny gas tanks, and glucose as the gas that refills those tanks. You don't want to overfill the tank, so it's important to pay attention to how much fuel you're ingesting. A good goal is 100-250 calories. The addition of protein in your snack also helps with muscle repair, and is especially important after resistance training. Examples of great post-workout snacks are as follows:
To drive home the importance of eating after a workout, understand that if a snack is delayed for more than an hour, the ability for muscles to use that fuel for stored glycogen is seriously decreased. This in turn will affect your next workout, because your muscles aren't properly fueled. By getting into the practice of eating before and after exercise, you will be properly fueling your body with the nutrients that will help to continually improve your workouts. And, by providing your body with the right amount of energy when you actually need it, you will be improving your ability not only to lose weight, but keep it off.