(CNN) Scientists have long known that what you eat before, during and after you exercise can make or break a workout and possibly affect your fitness results.
So what do nutritionists recommend to munch on? It turns out that quality carbohydrates are important pre-workout and lean proteins post-workout, experts say.
Before you exercise, eat carbs, but not too much, said Nancy Cohen, a professor in the department of nutrition at the University of Massachusetts in Amherst.
She recommended consuming 1 to 4 grams of carbohydrates per every 2.2 pounds of body weight if you are planning to exercise for longer than an hour. To put that in perspective, a medium banana has about 27 grams of total carbohydrates.
The Dietary Guidelines for Americans recommends that if you get 2,000 calories a day, aim to consume between 225 and 325 grams of carbohydrates, according to the Mayo Clinic.
When should you eat? About an hour to four hours before working out, Cohen said.
A review paper by researchers at the University of Sydney in Australia suggests that carbohydrate ingestion can improve endurance exercise performance. The paper was published in the Journal of Nutrition in 2011.
The researchers assessed 50 previous single- or double-blind, randomized studies on carbohydrate ingestion and endurance exercise. The researchers concluded that the data in the studies provide evidence that consuming carbohydrates can enhance endurance exercise performance in adults.
Research on how quality carbs can influence exercise performance -- especially endurance exercise -- dates to the 1930s.
"By eating carbohydrate-rich foods that are low in fat and low or moderate in protein, you can make sure you have enough muscle glycogen as fuel for your physical activity. This might include low-fat granola bars, fig bars, a peanut butter and jelly sandwich, banana, yogurt, pasta or other high-carbohydrate foods," Cohen said.
"Sufficient fluids are also important," she said. "In general, you can consume 5 to 10 milliliters of water per kilogram of body weight in the two to four hours before a workout."
If you prefer to break a sweat in the morning, experts are divided on whether you should eat ahead of time.
It should be your own decision on whether to eat breakfast before or after exercise, said Stuart Phillips, professor at McMaster University in Canada and director of the McMaster Center for Nutrition, Exercise, and Health Research.
"I work out before breakfast every day because that's when I like to work out. I don't take in anything other than perhaps a cup of coffee most times or perhaps a slice of toast. My big breakfast comes after. But that's not to say that's good or bad. That's just what I do," Phillips said.
However, Cohen said that it's important to not make a habit out of exercising on an empty stomach.
"If you haven't eaten in a long time, your body is in a fasted state. Normally, your body will use glucose for fuel and begin to break down muscle glycogen to deliver the glucose your body needs for exercise. In a fasted state, the muscle glycogen will be depleted sooner. Your body will then turn to breaking down fats for the energy it needs," Cohen said.
"This can lead to ketosis, or keto-acid buildup in the blood, which can be harmful to the kidneys over the long term and cause fatigue and dizziness," she said. "While exercising on an empty stomach may burn fat, it does not seem to be beneficial in the long run. And, if the fatigue means that you are not able to exercise at full performance, then you will also not be able to sustain as effective a workout."
Try eating eggs, cereal and milk, toast with peanut butter, or fruit and yogurt to fuel a morning workout, Cohen recommended.
One of the most important things to do during exercise is hydrate -- and if your workout is 45 minutes or less, fluids may be all you need to keep you going, Cohen said.
"For endurance exercises of one to 2½ hours, aim for 30 to 60 grams of carbohydrates per hour. This will provide carbohydrates to fuel the exercise to supplement the muscle glycogen," Cohen said. For instance, a medium apple has about 25 grams of total carbohydrates.
"Depending on the sport and the comfort of the individual, a range of foods or beverages could be useful here," she added. "Juices, sports drinks, granola bars, fruit and other high-carbohydrate foods and drinks can be helpful."
Phillips agreed, saying liquids are more easily digested.
"Solid food sits in your stomach, and for many people, that creates discomfort. So, mostly liquid," he recommended.
After you exercise, munch on protein, Cohen said, such as dairy products, eggs, meat and poultry.
"After long or very high-intensity workouts, consuming 1 to 1.2 grams of carbohydrate per kilogram of body weight per hour for four to six hours, along with 15 to 25 grams of protein within the first hour after exercise, will replenish muscle glycogen stores as well as support muscle protein synthesis," Cohen said.
For perspective, one hardboiled egg packs about 6 grams of protein.
"After lighter workouts, eat a well-balanced meal -- including high-quality protein and carbohydrates -- within two to three hours after finishing, and drink enough fluids to replace losses," Cohen added.
What happens if you experience muscle pain after you exercise? Some studies suggest that certain fruit juices, such as watermelon juice and cherry juice, can reduce muscle soreness after exercise.
For a small study published in the Journal of the International Society of Sports Nutrition in 2010, 54 healthy runners ran an average of 26.3 kilometers, or 16.3 miles, over a 24-hour period.
Some of the runners were instructed to drink bottles of tart cherry juice twice daily for seven days prior and on the day of the run. Others were given a placebo drink. Then, the runners were asked to assess the level of pain they felt before and after the run.
The researchers, who reported no conflicts of interest in the study, found that the runners who drank the cherry juice reported a significantly smaller increase in pain after the run compared with the placebo group.
All in all, a post-workout routine should include fluids to rehydrate, carbohydrates to refuel and protein to repair, Phillips said.
"In recovery, we talk about three Rs," he said of the post-workout routine. "Thus, I like sources that provide all three, like fluid milk or a smoothie made from milk and yogurt with berries."