Dante Dettamanti
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   Sports Nutrition

by Dante Dettamanti, BS, MS

Does Diet Make a Difference in Your Performance?


As mentioned in the last months article on “Nutritional requirements for water polo players”, the foods that you eat provide the potential energy, or fuel, that your body needs in three forms: carbohydrate, fat and protein. Consuming enough calories, or fuel, each day is the key if you want to perform well in practice and in games. But the more arduous the activity, like water polo, the more important it becomes to consume the proper mix of the three energy supplying nutrients. All three are important for the water polo athlete; but the primary limiting factor in performing water polo in practices and games are CARBOHYDRATES!

This article will be devoted to learning what kinds of carbohydrates to eat, when to eat them, and how to restore them in your body after you have used up the supply that is stored in your body. (Proteins and fats will be discussed in next month’s article). Carbohydrates, such as sugar and starch, are readily broken down into glucose, the principal energy source of the body. Glucose can be used immediately, or it can be stored in the muscles and liver as glycogen. During exercise, glycogen is converted back into glucose and can be used a fuel by the muscle fibers. Not only is glycogen the most significant source of energy for muscle contraction in high intensity exercise; but it is also a source of energy for brain function both during rest and exercise.

If an athlete wants to train and compete efficiently, he needs a full tank of glycogen every time he exercises. This can only come from food sources. Frequent long and hard training sessions and games can reduce the amount of glycogen available. The likely cause of poor performance and fatigue in practice, or in games, is because of low levels of glycogen in the muscles. Studies have shown that the glycogen stored in the body will start depleting after only one hour of continuous exercise. It can be depleted completely if not restored through diet and rest.

The limiting factor on performance, therefore, even during moderate intensity exercise, remains the bodies limited carbohydrate stores. No matter how ample your fat stores, after you deplete your muscle glycogen stores you will experience fatigue to some degree, and be unable to maintain the pace and intensity required in practice and a game.

Graph A below shows a hypothetical situation for a water polo player starting the training week on Monday with a large amount of glycogen stored in his muscles and liver. After completing a strenuous 2.5 hour water polo workout he will use up a large portion of the glycogen that was stored. After eating a high carbohydrate dinner that night and breakfast and lunch the next day, he can restore a lot of the glycogen that was used up. However, he will not completely restore the full amount, and will consequently start the next day’s practice with less than he had the previous day. This cycle is repeated every day, until about the fourth day, when the glycogen is almost completely depleted. Now what happens if you have another practice on Friday and a game on Saturday. How well do you think you will perform in that practice and game if something is not done to increase the amount of stored glycogen that you start the game with?

GRAPH A: Depletion of glycogen after four days of intense practice


There are only two ways to restore the glycogen levels in a body. Burn less calories (glycogen) by resting with easier training sessions; and/or by eating a carbohydrate rich diet. A case in point for a high carbohydrate diet was a study done with Ice Hockey players, a sport very similar to water polo in terms of intensity and burning energy. As in a water polo game, muscle carbohydrate (glycogen) is a major source of fuel; and declines anywhere between 38 and 88 percent. Muscle glycogen depletion relates closely to muscular fatigue.

A motion analysis of elite hockey players showed that the players with a high carbohydrate (60% of total) diet skated not only 30% more distance, but also faster than the players who ate a standard low-carbohydrate (40%) diet. In the final period of the game, when a team either wins or loses the game, the high-carbohydrate group had more energy and skated 11% more distance than they did in the first period. The low-carbohydrate group skated 14% less.

The bottom line in this and other studies of high intensity sports, is that both diet (more carbohydrates) and rest are critical factors in performance. Resting for several days and eating a low-carb diet was not effective in increasing performance. Neither was a high carbohydrate diet and not resting. Both must occur for maximum restoration of glycogen and maximum performance to occur. Water polo coaches should take note. If you want your team to perform well in an important game, then you had better rest them a few days by cutting back on the length and intensity of your workouts, along with encouraging the players to add more carbohydrates to their diet.


Most athletes that perform strenuous physical activity for several hours daily require a diet that is high in carbohydrates, a minimum of 55-65 % of the total food intake.  Player’s diets should also include about 20-30 % protein for muscle and enzyme build up, and about 20 % of the good mono and poly-unsaturated fats. How much carbohydrate should you eat? Plenty, if you are a water polo player who trains several hours a day of high intensity exercise. Most adults eat only 150-250 grams of carbohydrate a day. That might be OK if you are sedentary. That is certainly not enough to fuel an athlete’s body.

Most elite athletes need a lot more than the normal person, probably anywhere from 400-600 grams a day, depending on your training level, intensity and amount of training, gender, size, etc. Most water polo players, performing at a high level of training for ten-plus hours per week, will need about 3-4 grams of carbohydrate per pound of body weight. So, if you weigh 150 pounds, you will need between 450 to 600 grams per day of carbohydrate


Just to give you an idea of what a gram of carbohydrate is, consider that a banana has about 20 grams, a large potato has 30 grams, a cup of fruit flavored non-fat yogurt has 24 grams, a sandwich with a lot of bread and some lean meat has 50 grams, while a plate of pasta has about 80 grams. Other good sources of carbohydrates include whole wheat breads and cereals, rice, beans, corn, fruits, and fruit bars.

It seems that it might take a lot of eating to get to 450-600 grams. There are several ways to accomplish this feat! One trick is to cut back on fatty foods to make room for more carbohydrates. Fats have a tendency to fill you up, and should be used sparingly. Instead of piling on tons of cheese and meat sauce on top of your pasta, eat the pasta with tomato sauce and sprinkled with a little parmesan cheese on top. Instead of eating french-fries that are loaded with saturated fats, eat baked potatoes or sweet potatoes and go light on the sour cream and butter. Milk is a great source of calcium and fairly good source of carbohydrates, but drink 1-2% fat milk or non-fat milk instead of whole milk.


Try eating within two hours after training. This is the time when the body is more acceptable to carbohydrates and has the ability to store more glycogen in your muscles and liver. Eating after training is not always easy to do, especially if your team has an early morning training session, and you have to go to class right after training. Bring some food with you to morning practices for eating after training; something that you can carry and is easy to digest.

Fruits like bananas and apples, and food-bars are easy to carry; or if you can stop at a fruit/smoothie bar and get a fruit smoothie. Smoothies are a great source of carbohydrates, they go down quickly, and they digest quickly. Watch the ones that are high fat though. Many fruit/smoothie bars will list the ingredients in their smoothies, and will also list the percentages of fat, carbohydrates and proteins. Pick the ones with the most fruit and the least amount of fat.

Food bars (sport/energy bars) are a great way of meeting some of your carbohydrate needs and are easy to carry with you in your backpack. Make sure that you get high carbohydrate/low fat bars. Read the label and apply the 4 and 20 rule. Any bar that provides more than 20 grams of carbohydrate and less than 4 grams of fat is a good choice. Also, make sure that you drink water with your food bar to aid in digestion. If you can’t meet your carbohydrate needs with three meals a day, try snacking between meals with food bars, fruit, fruit muffins, half a sandwich, anything that you can think of that provides some carbohydrates.

Remember that food bars are to be used as a supplement to your meals, or as a snack food; not as a complete meal. Don’t overdo it with these bars and think that you can eat many of them every day, and not eat any other necesary foods. One or two a day as an in-between meal snack, under the guidelines as described above, should be the maximum for an athlete.


Water polo players should be adding meals rather than skipping meals. Three meals a day plus two light snacks should maintain the proper amount of carbohydrates for the water polo player. The meal that is missed the most is breakfast, especially if the team has an early morning practice session. It is difficult to eat breakfast after a morning workout. There simply is not enough time before you have to rush off to class. If that is the case, athletes should carry food in their backpack that they can eat quickly.  Sports bars, fruit, muffins, and sports drinks with some sugar and no caffeine are good sources of quick carbohydrates for a rushed breakfast.


There are several ways of determining if you are getting enough carbohydrates. Probably the best way is how you feel. Everyone gets fatigued during a hard practice or game; but if you are still fatigued at night or the next day, if your performance in practice and games is lacking, if you aren’t mentally alert, if you are tired all of the time and you can’t seem to keep your weight at a normal level, then you probably need more carbohydrates in your diet.

If eating more and adding snacks doesn’t work, then you might consider carbohydrate supplements. Supplements are available as gels and in liquid form. Marathon runners or tri-athletes that train many hours a day, and who start losing a lot of body weight usually use them. When the body runs out of glycogen, it turns to fats and proteins as a source for producing ATP. Burning fats is not much of a problem; but burning protein can be. Utilizing body protein means that a person is essentially using muscle tissue for energy. Not what an athlete would want if he wants to perform well.

During a ten-hour triathlon race, the body cannot store enough glycogen to get through the entire distance. So, many tri-athletes ingest high-glucose gels, or other high carbohydrate sources, during the actual race. Water polo players probably would not need this kind of supplement during a game or practice; but it might be a way to replenish your carbohydrates between games, when you have several games in one day. Pre-game and in-between game meals will be discussed in a future article.


Yes, even if you are playing in a pool full of water, you can still sweat and loose body fluids. Do you need to drink 8 glasses of water a day as some nutritionists recommend? It depends on several factors: How hot is the air and water temperature, how hard and how long you practice, and how much food you eat that contain large amounts of water. Thirst is usually a good indicator of your fluid needs; but when you are participating in physical activity in warm weather, you might not feel thirsty.

Athletes should start drinking before they start feeling thirsty, and continue drinking small amounts of water during training in warm conditions. The color of your urine is a good indicator of body fluid needs. Yellow or yellow-orange color indicates water stress, while nearly clear or light-yellow means that you are well hydrated. Foods also can provide certain amounts of fluid in your diet. If you keep track of your water needs and hydrate ahead of time in hot weather, you should be fine. If you start to feel light headed or nauseous, then you are possibly suffering from dehydration.


Sports drinks are not only a great source of carbohydrate to help fuel your muscles; but also a great source of fluid for your body. Be careful that the sports drink that you drink does not contain too much sugar. Drinks that are have more than 8% sugar interfere with water absorption from your stomach. You may end up with a full and bloated stomach and very little fluid in your body where it is needed. Check the label. If it has more than 8 grams of sugar in 100 ml of volume, then it is too high in sugar. Also, make sure that you are getting a sports-drink and not an energy-drink. The energy from an energy-drink comes from huge amounts of caffeine, and not a lot of sugar. Caffeine will not help you perform better if you need more sugar to fuel your muscles.


Some athletes feel that they can eat just about anything they want and still perform well in their event. This simply does not work! Athletes should educate themselves about what they need to eat, what foods provide what they need, and about the quality of the foods that they do eat. Things like eating whole grains, instead of refined white grains add quality to your meals. Educating yourself to eating right can go a long way in helping you achieve your peak performance in water polo games. Don’t just take a chance by eating everything in sight and hoping that everything will work out for you.

An example of this is a friend of mine who was going to compete in a triathlon. He wanted to carbo-load the day before the race. Thinking that he was going to have a high carbohydrate meal, he ordered a huge pizza with pepperoni and double cheese. Little did he realize that of the 1800 calories in the pizza, 1200 calories were fat and protein from the pepperoni and the cheese, and only 600 calories of carbohydrate came from the tomato sauce and the dough? The fat and protein contributed nothing to his triathlon as far as energy use (your muscles need carbohydrates), and consequently he did poorly in his race. Many months of hard training down the drain because he didn’t know what the effects of eating the pizza were, and that only a third of the pizza contained much-needed carbohydrates. Much less than he really needed.

Next month’s article will go into more detail on what an athlete should eat, and how to go about eating nutritious meals.