Though most of the visible work needed for a fit body takes place at the gym, the real "magic" happens during rest. Exercise causes damage to muscle tissue which the body repairs during the recovery process. The recovery process is technically what makes you bigger, faster and stronger. This important process is dependent on an adequate amount of rest and nutrients. Because a large part of muscle repair happens during sleep, good nighttime nutrition is crucial for a speedy, effective and complete recovery.
Nighttime Energy Needs
The main argument against nighttime eating centers around the myth that "late calories" turn into unwanted weight gain. The truth is that only an excessive calorie intake leads to unwanted weight gain regardless of meal timing. Though the body's metabolic rate and energy needs decrease at night, the body is still working and therefore, needs calories.
Exercise causes damage to muscle tissue which the body treats as an injury. Exercise breaks muscle tissue down while recovery builds muscle tissue up. The recovery process heals the muscle making it bigger, stronger and faster. Recovery requires energy. Much of the recovery process happens during sleep, increasing the body's need for energy. Ignoring nighttime nutrition leads to ineffective recoveries and slows down fitness progress.
Slow Digesting Foods
The best option for nighttime meals are foods which are digested slowly. Slow digestion helps the body better utilize energy throughout the entire night rather than all at once. Good examples of nighttime options include complex carbs (100% whole wheat products, brown rice, beans, vegetables, legumes), lean proteins (soy, chicken breast, eggs, low-fat dairy products - milk, cottage cheese, tuna, protein shakes that contain casein) and unsaturated fats (seafood, olive oil, peanut butter, nuts, seeds).
Foods high in sugar are poor nighttime options because they are digested very quickly. Sleep deprives us of food for 6-8 hours. This fasting is detrimental to the recovery process. Sugar passes through your system very quickly; whatever energy isn't used right away is stored as fat. Because the body doesn't always like using body fat for energy, there is the potential for it to burn through muscle for nighttime energy needs.
Body Fat/Unwanted Weight Gain
Those who argue against eating late claim nighttime calories lead to unwanted weight gain. The truth is unwanted weight gain happens because of a calorie surplus; eating too much throughout the entire day. The relationship between how many calories you burn and how many you consume (known as calorie balance) controls weight; how much is more important than when.
The Bottom Line
Fitness gains are dependent on a solid recovery process. Recovery requires an adequate amount of rest and nutrients to propel you to new fitness heights. Eating at night does not lead to unwanted weight gain given your overall calorie intake is under control. Eating the right foods at night ensures an adequate amount of nutrients to fuel improvements.