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Nutrition and Performance in Sport

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Christophe Hausswirth

Chapter 5. Nutrition and physical composition

Topic 1. Reducing fat mass and weight: strategies and potential risks for high-level athletes

Nathalie Boisseau

Résumé

The strategies used by athletes to reduce body weight and control fat mass aim to favour performance while increasing the ratio between lean and fat mass.
In high-level athletes, as daily energy expenditure is high, the best strategy when seeking to lose weight and reduce fat mass is to decrease the total energy intake. Some strategies aiming to limit appetite can also be suggested. From a practical point of view, various approaches are possible, including modulation of meal frequency, high-protein diets, increasing glycogen storage, high-intensity intermittent exercises, etc.
Body weight changes must be progressive, implemented exclusively during training periods, and should not involve significant energy restriction or high-risk behaviour. On average, the weight-loss aimed for should be around 0.5 to 0.9 kg/week, but should never exceed 1.5 kg of body weight per week. Indeed, most of the time significant weight reduction reflects dehydration, nutritional deficiencies and sometimes proteolysis; all of which have negative effects on physiology, nutritional status and performance.
Psychological pressures exerted by the athletes’ entourage can induce significant behavioural disorders, including eating disorders. Educational programmes for coaches and athletes could help to limit some dangerous practices which are still observed (mainly in “aesthetic” sports or in weight-category sports).

Texte intégral

1. Introduction

1Many athletes wish to lose weight and fat mass to enhance their performance, their appearance, or to reach their target weight before a competition. Whatever the case, the objective is to reach a level of excellence which has been made uncertain by a few extra kilos. Sports in which aesthetics contribute to performance, weight-category sports or sports where lanky builds are the norm require a very precise control of weight and fat mass. The practices to which athletes resort to achieve this control may be risky, and the fat mass levels observed in high-level athletes are sometimes non-physiological. Thus, the expected fat mass levels vary between 10 and 22% in men, and between 20 and 32% in women; but extreme values are regularly mentioned in scientific works, such as 5% and 12% in men and women, respectively, who practice sports at a high-level.

2The aim of this chapter is to suggest appropriate ways in which high-level athletes can lose weight and fat mass. The potential risks associated with these practices will also be discussed.

2. Strategies to reduce fat mass and lose weight used by Olympic athletes

3Any weight-loss strategy requires an understanding of the notion of energy balance. The energy balance (EB) is defined as the total energy intake (TEI) minus the total energy expenditure (TEE). Thus, food intake and the energy expenditure due to physical activity define the plateau around which body weight and fat mass are regulated. If total energy intake exceeds energy expenditure (TEI>TEE), the subject will put on weight. While if total energy expenditure exceeds total energy intake (TEI<TEE), the subject will lose weight. For overweight subjects who wish to lose weight, two strategies are possible and can be combined: a decrease in food intake and/or an increase in energy expenditure through an increase in physical activity.

2.1 Increasing exercise-related energy expenditure

4Several strategies including physical exercise can be used to lose weight and control fat mass. Several processes significantly increase the use of fat mass from the body’s stores (Brun et al. 2011). These strategies are as follows:

  • constant low-intensity exercises (including work at Fatmax or lipoxmax);

  • very regular physical activity (in the long term, this favours the capacity to mobilize and oxidize lipids at rest and during exercise);

  • prolonged high-intensity exercise (stimulating the use of lipids after decreasing glycogen stores);

  • recovery after intense exercise or high-intensity intermittent exercise (due to compensatory mechanisms).

5In high-level athletes, adding low-intensity training sessions to promote regulation of body composition is not recommended as high-level sport requires high amounts of training, and high intensities will favour speed, strength or explosive power production. For these reasons, this strategy appears inappropriate. In addition, the three other strategies mentioned are already used as part of the high-level athlete’s normal routine (regular practice, high-intensity and concomitant recovery). Thus, the only way to favour fat mass reduction and promote weight loss in high-level athletes is to control food intake. As a consequence, this approach is the main one used in sports associating aestheticism and slenderness, and in weight-category sports (Kordi, 2009).

2.2 Reducing energy intake

6The reduction of energy intake is, in fact, the main strategy used by athletes. In the short term, this will involve a quantitative approach aiming to reduce the kilocalories absorbed. However, calorie restrictions can be risky since they can generate some food imbalances affecting the athletes’ physical and/or mental health (see below, “3. Potential risks of these practices”). In the long term, a qualitative approach should be applied to attempt to modify the athlete’s eating habits. Even though this approach is recommended (because it is less damaging), it can be hard for athletes to maintain in the long term.

7Quantitative approach. For optimal and safe weight loss, it is recommended to reduce energy intake by 500 to 1000 kcal per week (Garthe et al. 2011). The total daily energy intake can be reduced by decreasing the total number of kilocalories consumed by limiting the percentage of lipids and reducing intake of carbohydrates with a high glycaemic index. Any weight adjustment must be progressive, and should only be attempted during training periods, without excessive restrictions and without using high-risk products or techniques (Turocy et al. 2011). The following is a non-exhaustive list of dangerous behaviours: fasting, purging, vomiting, excessive use of appetite suppressants, use of sauna and diuretics for water loss, even doping (ß2 agonists such as clenbuterol or salbutamol).

8Qualitative approach. General recommendations can be given relating to portion size, cooking methods, decreasing dietary fat, eating low-energy snacks, adding fibre, eating carbohydrates with a low glycaemic index (without forgetting an adequate protein and micronutrient intake). In addition, stressful situations, “slack periods” (waiting time during competitions, travelling) and the temptations to eat novel foods when abroad must be avoided since they favour weight gain.

9A decrease in energy intake can also be obtained indirectly by modifying various parameters regulating appetite.

2.3 Other strategies based on appetite control

10It is well known that modifying the energy balance leads to changes in body composition. Based on energy intake and physical activity, subjects can modify their total daily energy expenditure and restructure their energy balance through feed-back mechanisms. These adaptations are known, but very few data in the scientific literature allow us to extend the existing relationship between physical activity and appetite to the specific case of high-level athletes (Fig. 1).

Figure 1: Energy balance, physical activity and appetite.

Figure 1: Energy balance, physical activity and appetite.

11High-intensity exercise and appetite. It is well known that high-intensity exercise favours a transitory loss of appetite (exercise-induced anorexia) (Imbeault et al. 1997). This state is partly induced by an increase in anorexic peptides (PYY and GLP-1) and a decrease in ghrelin (orexigenic peptide). These effects appear more prevalent in men (Pomerleau et al. 2004). Even though it is known that regular high-intensity exercise chronically decreases appetite and thus generates weight loss in the general population, at present there is no data available on its effects in high-level athletes (Stensel, 2010). What is more, this hypothesis goes against the glycogenostatic theory which states that hunger is an adaptive mechanism, the role of which is to replenish glycogen stores (Flatt, 1987). Indeed, as high-intensity exercise preferentially uses carbohydrates, and thus glycogen stores, it should stimulate hunger, rather than limit it (Hopkins et al. 2011). And yet, in practice, athletes who increase their training intensity change their body composition, with a significant reduction in fat mass. What adaptation mechanisms could explain this phenomenon? The work of Pillard et al. (2010) can partly answer this question. By comparing three situations (rest, exercise at 35% or 70% of VO2 max), these authors showed that a greater amount of lipids are oxidized during exercise performed at 35%. However, during recovery over the following 6 hours, the total amount of lipids oxidized becomes greater in the group who performed the exercise at 70% (Fig. 2). Based on these observations, it is not high-intensity exercise that causes weight loss and reduces fat mass, but the subsequent recovery. This theory is reinforced by studies investigating high-intensity intermittent exercise (HIIE). These studies show that training involving HIIE over 15 weeks leads to a greater loss in total abdominal fat mass than with constant low-intensity training (Trapp et al. 2008). The mechanisms causing these differences have not been totally elucidated, but they could be linked to an excess of post-exercise oxygen consumption (EPOC) if the intensity of exercise is greater than or equal to 70% of the VO2 max (Bahr, 1992). This increased consumption of oxygen during recovery allows the oxidation of free fatty acids which were first mobilized during exercise.

12Other strategies regulating appetite control. Increasing protein intake inhibits the mechanisms triggering hunger and thus reduces food intake (Porrini et al. 1995). However, the type of proteins ingested modulates this effect; fast proteins such as whey are more efficient than slow-proteins such as casein or albumin (Bowen et al. 2006). Increasing meal frequency can also promote slimming, stimulate the metabolism, decrease hunger, and help prevent eating between meals by favouring glycaemia and better control over insulin production (Leidy and Campbell, 2011). The time spent at the table (i.e. the absorption speed) is also inversely correlated to weight gain and increased fat mass, whatever the age and the body mass index of the subject (Tanihara et al. 2011). It is therefore recommended that athletes stay long enough at the table (about 40 to 45 minutes) and that they be discouraged from considering the meal as a loss of time. A trip to higher altitude (hypoxia) is likely to reduce appetite (Snyder et al. 2008). However, as previous reports indicated profound appetite reductions as a result of exposure to extreme altitudes, this strategy appears to be of limited utility in high-level athletes (Westerterp-Plantenga et al. 1999). Similarly, even if exercise performed at a high ambient temperature is not associated with higher energy intake in the subsequent meal, whereas exercise in a neutral environment is (Shorten et al. 2009), this type of approach cannot be recommended for athletes.

2.4 How should you lose weight?

13Weight loss must be progressive and not exceed 500 g to 1 kg per week (Rankin, 2002). To achieve this level of weight loss, a daily energy restriction of 500 to 1000 kcal seems necessary. This level of reduction can be quite difficult for athletes whose energy intake is already very low (Garthe et al. 2011). A more extreme diet can lead to a loss of lean mass (including muscle mass), but also of strength or power, and thus reduce performance (Garthe et al. 2011; Degoutte et al. 2006; Koral and Dosseville, 2009). Some recent studies also showed that, for a weight loss of about 4 to 5 kg, it was better to restrict the weekly energy intake by 7% (or-19% of the total daily energy intake [TDEI]) rather than to decrease daily intake by 1.4% (equivalent to-30% of TDEI) (Garthe et al. 2011). In the second case, it takes 5 to 7 weeks to lose the 4 to 5 kg, but this weight reduction is associated with significant loss of lean mass (and therefore of muscle mass). In contrast, the slower diet (4 to 5 kg lost over 9 to 12 weeks) has no impact on lean mass.

3. Potential risks of such practices

14The major risk of any strategy used to restrict weight and fat mass, is of being off form, and performing poorly. In a study carried out on 272 kick-boxers, Garthe et al. (2011) showed that more or less severe energy restrictions before the competition could generate a loss of coordination, motivation, endurance, strength, general physical state and well-being in men. The consequences in women were equally injurious, but appeared less extensive (report for “The Norwegian School of Sport Sciences” in 2004).

15Finally, according to the scientific data, the age at which athletes go on their first diet seems early (Sundgot-Borgen and Garthe, 2011). Indeed, without distinguishing between sports, 15% of high-level athletes go on their first diet between the ages of 10 and 15.

16The following table shows a few negative consequences of restricting energy or water intake too severely.

Water and food restrictions, and consequences on health (non-exhaustivelist)

Growth and maturation

▪ Sexual maturation can be retarded in gymnasts (Caine et al. 2001).
▪ Growth at puberty is sensitive to nutritional factors. Low circulating IGF-1 levels and lower concentrations of IGFBPs are then observed (Smith
et al. 1995).
▪ Bone mineral density can be definitively altered in young athletes with chronic energy restriction (Deutz
et al. 2000).

Chronic fatigue, injuries and weaker immune system

▪ Frequent episodes of chronic fatigue, injuries and weakness regarding diseases are noticed in the athlete during severe energy restrictions (Sundgot-Borgen and Garthe, 2011; Burke et al. 2004; Gleeson et al. 2004).
▪ In gymnasts with late menarche, the decrease in estrogen levels and a decreased consumption of proteins and calcium cause a risk of stress fracture (Loosli and Benson, 1990; Benson
et al. 1990).

Dehydration

▪ Dehydration states generate:
▪ a decrease in plasma volume without concomitant increase in heart rate
▪ a decrease in sweating rate, which favours hyperthermia
▪ a lesser activity of cognitive functions
▪ the apparition of cramps linked to micronutrient deficiency
▪ digestive disorders
▪ an increase in effort perception
▪ anxiety
▪ early fatigue
▪ nervous tensions
▪ anger… (Sundgot-Borgen and Garthe, 2011)
▪ ƒ anger… (Sundgot-Borgen and Garthe 2011).

Food efficiency

▪ Food deficiency is defined by the ratio between weight variation and the kilocalories ingested.
▪ It is thus an index indicating how many calories an athlete can eat to maintain a stable weight. Food efficiency increases after repeated yo-yo diets (so a great weight change), which partly explains the growing difficulty to maintain a low body mass on a prolonged period (Brownell
et al. 1987).

Eating disorders

▪ Athletes who practise activities requiring a very fit profil? (very low-fat mass) are more likely to develop eating disorders (Sundgot-Borgen, 1996). Indeed, 62% of high-level athletes could suffer from eating disorders (Bonci et al. 2008).

4. Conclusion

17The lack of specific literature makes it difficult to recommend strategies for weight and fat mass reduction in high-level athletes. Approaches may differ depending on the sport practised, but also on the athlete’s personality and eating habits. Any weight and fat mass changes should be slow and must take place only during training periods. Applying strategies which are too rapid, associating high-risk products or behaviours, should be prohibited by the athlete’s entourage, so as to preserve health, of course, but also performance levels.

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Table des illustrations

Titre Figure 1: Energy balance, physical activity and appetite.
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