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Nutrition and Performance in Sport

Christophe Hausswirth

Chapter 5. Nutrition and physical composition

Topic 19. Rapid variations in body weight

Yann Le Meur, Véronique Rousseau, Amélie Fosse, Christophe Hausswirth, Axel Heulin et Eve Tiollier

Texte intégral

Questions and answers

École Lenôtre

Key points
■ In sports with weight categories, athletes often go on slimming diets to rapidly lose weight coming up to a competition. If this type of diet is not controlled and monitored, it can generate physiological disorders affecting both health and performance.
An athlete can lose up to 4% of their body mass during the week preceding a competition, especially by accelerating dehydration. If the weight loss is to exceed this level, it must be anticipated and should begin during the preceding weeks, based on a progressive slimming diet.
When an athlete wishes to lose weight quickly, calorie intake must mainly be restricted by reducing carbohydrate and lipid intake. However, the carbohydrate intake must not be less than 4 to 5−1.d−1 (in a proportion of 20% of the total energy intake). This level of intake will preserve the athlete’s immune system and their training capacity.
In general, rapid weight loss is associated with a decrease in muscle mass and physical capacities. For the high-level athlete, it is essential to limit these reductions by maintaining a high daily protein intake, of about 1.6−1.d−1. After training, it is highly recommended that athletes consume a recovery drink rich in carbohydrates and branched-chain amino acids.
After the weigh-in, water and calorie intake must be planned and controlled, so as to avoid exceeding the body’s absorption capacity. When developing the hydration plan, it should be kept in mind that the maximal gastric emptying capacity is approximately 800 ml per hour, thus there is no point in exceeding this limit. Similarly, even if the post-weigh-in meal should contribute to replenishing glycogen stores by favouring carbohydrate intake, this intake should be divided and not forced down.

How can athletes cope with alternating progressive slimming diets and rapid weight-loss strategies during the season?

2To reach their target weight before a competition in a discipline with weight categories, the best strategy – for the athlete’s health and performance – is to adapt their eating behaviour several weeks before the competition. This strategy will result in progressive weight loss (see Fact sheet No. 20 Fat mass reduction, p. 469). If this approach does not result in adequate weight loss to attain the target weight, it is always possible to lose up to 4% of body mass during the few days preceding a competition. In this context, it seems wise to determine the speed at which an athlete loses weight during a period of progressive weight loss. By doing this, it will be possible to plan how long before the competition the progressive diet must start: for instance, a wrestler weighing 75 kg who wishes to compete in the “under 66 kg” category and who normally loses 1 kg per week when following a progressive weight-loss diet, must weigh 69 kg one week before the competition and should thus start a progressive diet at most five weeks before.

3To lose the last extra kilograms before a competition, a rapid slimming strategy can be implemented, involving significant water loss. Indeed, some studies indicate that a loss of 5 kg over ten days, in non-obese individuals, is the result of water loss (54 to 58%), reduction in fat mass (30 to 35%) and reduced muscle mass (6 to 16%). Ideally, athletes should avoid losing more than 4% of their body weight in the last week before the competition, especially if the weigh-in takes place on the first day of the competition. Indeed, under these circumstances, the athlete does not have enough time to rehydrate before the beginning of the competition. Since the maximal capacity of gastric emptying is 800 ml per hour, athletes would not be able to compensate for a serious water loss (i.e. greater than 4% body weight) in the time available. The athlete must also avoid becoming too severely dehydrated before a competition, since it is well established that extensive dehydration can generate hypovolaemia and a “failure” of thermoregulation processes. In addition, dehydration results in reduced irrigation of active muscles, as well as a decrease in the amount of muscle glycogen. Finally, in terms of physical qualities, several studies have highlighted an alteration of maximal strength and aerobic power, as well as an increase in reaction time in dehydrated athletes. These data confirm that, although it is possible to use water loss to reach a target weight before a competition, the extent of loss must always be reasonable (less than 4% of body weight) to avoid interfering with the athlete’s performance. From this point of view, limiting weight variations during the season and anticipating the implementation of restrictive diets as much as possible is the best strategy for athletes involved in weight-category sports.

How can loss of muscle mass be limited during a rapid slimming diet?

4Proteins. Calorie restriction inevitably results in some degradation of contractile proteins, the extent of the degradation depends on the duration of the diet. To avoid excessive loss of these proteins, the solution seems to be to increase the athlete’s protein ration. Some studies show that an intake of 1.6−1.d−1 is enough to maintain the athlete’s protein balance when following a calorie-restricted diet. However, the protective effects of a hyperprotein diet appear to depend on the proportion of branched-chain amino acids (leucine, isoleucine and valine) it contains. These amino acids directly impact protein synthesis at the cellular level, and also influence secretion of testosterone and growth hormone, favouring increased mobilization of lipid storage.

5Thus, in the context of a restrictive diet used to lose weight quickly, particular attention must be paid to post-exercise protein intake, more specifically after very intense training sessions and bodybuilding, because these types of session are often associated with a negative protein balance (when the extent of protein degradation exceeds protein synthesis). Some studies show that when proteins are provided rapidly after exercise the return to a positive protein balance is significantly faster. This effect appears to be observed when proteins are consumed up to three hours after the end of the training session; beyond this time window, nutritional recovery no longer fully replenishes proteins to the basal level measured before exercise. Therefore, when a restricted diet is planned this data must be taken into account, since calorie restriction increases the risks of generating a persistently negative protein balance. Along the same lines, some authors studied how consuming amino acids before exercise affected the protein balance during and after a bodybuilding training session. Their results showed that an intake of essential amino acids (the amino acids that cannot be synthesized in the body, and which must be provided by food) has a greater effect on protein synthesis if it is taken before the bodybuilding training rather than after. This strategy decreases the breakdown of amino acids during intense exercise and helps to rapidly restore a positive protein balance after the post-training snack. These results are particularly interesting for athletes who want to lose weight quickly but must preserve their muscle mass.

6Carbohydrates. A decrease in carbohydrate intake stimulates lipid oxidation at rest and during exercise, favouring fat mass reduction. Thus, it may be advantageous to reduce carbohydrate intake during a restrictive diet aiming to rapidly reduce weight. Nevertheless, it is important to underline that a minimal carbohydrate intake of 4 to 5−1.d−1 must be maintained to avoid perturbing growth-hormone synthesis, the immune system, and aerobic and anaerobic performance. Consuming carbohydrates during training sessions and competitions (mainly in the form of sports drinks) is thus recommended, since these carbohydrates are converted immediately into energy and therefore help to limit degradation of muscle proteins.

7Lipids. One gram of lipids provides twice as many calories as one gram of carbohydrates (9 kcal as opposed to 4 kcal, respectively). It is thus easy to understand that lipid intake must be strictly limited during a restrictive weight-loss diet. This rule is even more important as the body always has extensive lipid stores, even in athletes with a low fat mass. Scientific studies recommend reducing the proportion of lipids contained in food from 30–35% to 20% of total daily calorie intake. However, some lipids have a structural role and are involved in the synthesis of antibodies or some hormones; it is therefore important not to completely omit them from the diet. Consuming some high-quality fats (rapeseed oil, olive oil) will help to maintain the levels of essential fatty acids.

How can hunger pangs be limited during a restrictive weight-loss diet?

8Some studies have shown that the recurrence of hunger pangs and eating behaviour in the hours following a meal are influenced by how fast a meal is eaten. Thus, the faster an individual eats, the more likely they are to eat before the following meal. Because of this, spending sufficient time at table (at least 30 to 35 minutes; and ideally between 40 and 45 minutes) is recommended. This recommendation is particularly important during restrictive diets, when the urge to eat is often stronger. In addition, other studies indicate that dividing food intake into five or six portions during the day stimulates the metabolism, while also decreasing hunger and snacking, and favours control of glycaemia and insulin production. Even though these results have not yet been confirmed by other studies, they suggest that during a weight-reduction diet it would be a good idea to divide food intake throughout the day, planning a number snacks rather than the three traditional meals. Finally, these results show that it is not wise to skip breakfast when seeking to lose weight, as this type of strategy only favours a yo-yo effect.

How should post-weigh-in fluid intake be managed?

9Even though post-weigh-in fluid intake must be a priority for athletes who have used a rapid slimming diet, it is important to keep in mind that the stomach has a limited gastric emptying capacity. Thus, the body cannot assimilate more than a certain amount of water at any given time. The maximum gastric emptying capacity has been shown to be about 800 ml per hour when fluids are ingested regularly every 15 minutes; it is pointless to exceed this limit for post-weigh-in water intake. For example, a judoka who is weighed two hours before the first combat in a competition should consume about 1.6 l of sports drink, or water, before the combat, and must continue to rehydrate throughout the day, without exceeding 800 ml of fluids per hour. To favour good rehydration the drink should contain 1 to 1.2 grams of salt per litre. In this respect, drinking sparkling water or hot broth, which are both rich in sodium, can be an efficient strategy when the weigh-in takes place the day before an event. Hot drinks have an added advantage, since beyond the benefits of water and salt intake, athletes generally drink them more slowly, and thus the time necessary for the stomach to assimilate them is respected. When the weigh-in takes place on the morning of the competition, the most appropriate strategy is to add a pinch of salt to the drink athletes consume while waiting for the competition to start.

When and how should I eat when the weigh-in takes place the day before a competition?

10When the weigh-in takes place the day before a competition, the athlete has enough time both to limit catabolic processes (i.e. the use of muscle mass as a source of energy) and to increase their hepatic and muscle glycogen stores. Nevertheless, this should be done under supervision and in line with consumption indicators. In addition, athletes should be clearly reminded that immoderate calorie consumption is not appropriate.

11Ensure replenishment of glycogen stores. To favour the increase in glycogen stores before the beginning of a competition, the athlete must favour carbohydrate intake, especially during the last meal eaten the day before the competition, after the weigh-in. Several small snacks composed of ripe fruit, juice, fruit purée, fruit jellies, (low-fat) biscuits, rice or semolina puddings can help to optimize glycogen storage. As the body’s glycogen resynthesis capacity is limited, the athlete must never force himself to eat, and he must respect his digestive capacity. Digestion can be facilitated by limiting the consumption of fibre-rich foods (vegetables, unrefined products, etc.) or fats (butter, oil, cheese, etc.).

12Limit catabolic processes. Dehydration associated with a restricted calorie intake during a rapid slimming diet favours muscle catabolism, or the oxidation of muscle tissues, as an energy substrate. Consuming an energy drink containing branched-chain amino acids and another source of protein (white meat or fish) during the meal following the weigh-in, restores the athlete’s positive nitrogen balance.

When and how should I eat when the weigh-in takes place on the morning of the competition?

13Eating before the competition allows the athlete to achieve a better level of performance than when competing on an empty stomach. However, it is important to remember that it is during the two days before the event that most of the glycogen that will be used during the competition is stored. It thus seems preferable to avoid hearty meals after a weigh-in scheduled on the morning of a competition. In these conditions, the pre-competition food must be selected to help the athlete perform without any negative effects due to the digestive process. Based on this requirement, several recommendations related to pre-competition meal and snack can be made to athletes:

  • limit foods rich in fat or fibres to favour gastric emptying and reduce the risk of gastrointestinal problems;

  • consume a moderate amount of protein;

  • favour foods rich in carbohydrates to maintain glycaemia (cereals, pasta, rice, etc.);

  • adapt calorie intake depending on the time between the last meal and the start of the competition: if it is less than three hours, reduce food consumption.

14Beyond these general recommendations, athletes should adjust the characteristics of the pre-competition meal based on their individual preferences. Some, for instance, like to eat large amounts of food up to two hours before a competition, while others find it difficult to do so and prefer to have a light meal to limit gastrointestinal discomfort. It is thus recommended that various nutritional strategies be tested during minor competitions to identify which is best adapted to the athlete’s individual characteristics.

How should water and food intake be managed during the day of a competition?

15Athletes who lost weight quickly must be encouraged to keep eating and drinking throughout the competition. Firstly, this approach will help to balance the losses linked to performance, and secondly, the rehydration and energy replenishment started after the weigh-in will be pursued. In these circumstances, with a view to sparing the muscle glycogen stored for the competition, it is recommended that fructose be the main carbohydrate consumed. Athletes should therefore select a drink containing fructose and lactose (but should not drink more than 800 ml per hour), and regularly eat small snacks consisting of easily digestible food (biscuits, gingerbread, cereal bars, yoghurt or ripe fruit). Taking regular small meals throughout the day of the competition and a few sips of drink every 15 minutes is more efficient than a single large intake. However, it is important to avoid sodas or energy drinks, because their high sugar level leads to significant variations in glycaemia. These variations can induce reactive hypoglycaemia which significantly hampers performance.

Practical applications

1. Determine your profile

Image 10000000000003FB000002D81B5FA021.jpg

2. Conditions for rapid weight loss (= water loss)

16 Water loss affects physical and mental performance

17 It takes place as late as possible, in profile 2 athletes

18 It is tolerated, but must not be superior to 2% of body weight

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3. Learn how to regulate eating and drinking

Weigh-in the day before a competition (19 hours)

19 Choose to have a meal or small snacks

20 After the weigh-in, eat and drink immediately (depending on your tolerance)

21 Adapt the amounts consumed to correspond to your personal tolerance

22 Drink slowly. To facilitate this, drink hot savoury liquids, e.g. vegetable broth, fat-free chicken stock, broth with vermicelli

23 Divide eating and drinking:

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24The stomach’s maximal tolerance is 600 ml/h for women and 800 ml/h for men

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Weigh-in 2 hours before the competition

25 After the weigh-in, eat and drink immediately (depending on your tolerance)

26 Drink 150 ml to 200 ml of water every 15 minutes

Image 1000000000000023000000237AE8ED72.jpg The stomach’s maximal tolerance is 600 ml/h for women and 800 ml/h for men

27 Eat a sweet or savoury meal, depending on what you prefer

28 The amount of food to eat will depend on the time available for digestion, as imposed by the timing of the competition

29 Plan to snack during any break lasting more than 1 hour

30 As soon as you start warming up, have a sports drink (See Fact sheet No. 10 Hydration, p. p. 342)

Image 10000000000000210000002300BC0868.jpg It is essential to test food and drinks well before a competition

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Onion squash velouté with riso pasta

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Photo credit: Thibaut Ruggeri.

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31Serves 2

32Preparation time: 30 minutes

33Cooking time: 25 minutes

Difficulty: Image 10000000000000290000001F9AF7AF5B.jpg


35 350 g peeled onion squash

36 10 g olive oil

37 50 g onions

38 125 g reconstituted chicken stock

39 150 g semi-skimmed milk

40 2 g de granulated sugar

41 1 pinch of salt

42 Flat parsley for decoration

43Chop the squash into pieces.

44Sweat the chopped onions in olive oil.

45Add the squash, sugar, chicken stock and two-thirds of the milk.

46Simmer for 20 minutes.

47Blend, add the rest of the milk and season.


49 40 g riso pasta

50Coarse salt

51 Water

52 Vegetable oil

53Cook the pasta in a saucepan of boiling water with the salt and vegetable oil.


55Add the cooked pasta to the velouté.

56Decorate with flat parsley.


58You can serve this soup with slices of toasted bread.

59Chef’s note

60This dish, which is rich in sodium, favours rehydration while also providing the necessary carbohydrates for upcoming exercise.

61Nutritional analysis per person

Energy (Cal)

Carbs (g)



Lipids (g)

Protein (g)




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