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Nutrition and Performance in Sport

Christophe Hausswirth

Chapter 5. Nutrition and physical composition

Topic 20. Fat mass reduction

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

Texte intégral

Questions and answers

Key points
For high-level athletes, who generally have a high daily training workload, reducing daily energy intake rather than increasing energy expenditure is the simplest way to reduce fat mass.
Qualitatively, the best nutritional strategy to reduce fat mass is to:
– reduce the consumption of fatty, salty and sweet foods;
– cut out any alcohol;
– reduce the consumption of carbohydrates, but maintain an intake of at least 4 g carbohydrates per kilo of body mass per day, favouring food with a high glycaemic index;
– maintain protein intake to limit muscle mass reduction, while also maintaining appropriate micronutrient intake.
It is advisable, on the one hand, to eat slowly and stay at table (between 40 and 45 minutes) to favour satiety and, on the other hand, to divide food intake over the day rather than limiting it to the three main meals.
Weight loss should not exceed 1 kg per week (about 1.5% of body weight). Above this threshold, weight loss is only due to dehydration and reduction in muscle mass, both of which adversely affect performance.
It is important to set yourself reasonable targets and to limit diet periods during the year. Chronic food restriction leads neither to good health nor to high performance levels.

How should you adapt your diet to lose fat mass?

1Variations in an athlete’s body mass depend on their energy balance. This balance represents the difference between energy intake through food and energy expenditure due to basic bodily functions and training. To lose weight, the energy balance must be negative (i.e. calorie intake must be less than energy expenditure) for long enough.

2Two main strategies can be contemplated; they may be complementary. The first strategy consists in increasing the amount of training, in terms of volume and/or intensity, without modifying your eating habits. However, for high-level athletes this strategy is often hard to implement because they already have a very high training workload. The second strategy consists in reducing calorie intake through food. This strategy appears better adapted for high-level athletes, and the effects can be increased by simultaneously enhancing the quality of food intake.

3To be efficient, a restrictive diet must reduce daily calorie intake while ensuring adequate levels of carbohydrate, protein and micronutrients. Scientific studies have shown that daily energy intake can be reduced by 500 to 1000 kcal to promote weight loss (although a minimum intake of 2000 kcal is necessary to preserve the athlete’s health). When applying these restrictions, the athlete must:

  • Maintain an adequate carbohydrate intake. Even though it is advisable to reduce carbohydrate intake during a diet aiming to reduce fat mass, it should be at least 4 to 5−1.d−1 to maintain growth hormone synthesis, preserve the immune system and maintain the athlete’s performance level. During meals, carbohydrates with a high glycaemic index and foods rich in fibres should be selected to favour prolonged satiety and to limit eating between meals. Carbohydrates with a high glycaemic index must only be eaten during and after training sessions, since it is only in these particular contexts that they will be used as energy substrates or to replenish glycogen stores.

  • Maintain an appropriate protein intake. During a restrictive diet, it is important to maintain protein intake to preserve the athlete’s muscle mass. Otherwise, muscle atrophy can occur, decreasing the athlete’s strength and speed capacities. To avoid this outcome, it seems wise to schedule a snack containing branched-chain amino acids after any training sessions generating extensive muscle damage. This strategy will help limit the mechanisms of post-exercise protein degradation.

  • Ensure an adequate micronutrient intake. Micronutrients (vitamins, minerals and trace elements) are involved in all the major bodily functions, especially those necessary for physical exercise (energy metabolism, immunity, nerve transmission, etc.). Therefore, during a restrictive diet, athletes must be sure to maintain an adequate intake of micronutrients through food. To do so, it is particularly interesting eat beneficial to large amounts of fruit and vegetables. Not only are these foods very rich sources of micronutrients, they also have a low energy density.

  • Limit fatty, salty and sweet foods. The number of calories contained in one gram of lipid (9 kcal) is twice that contained in one gram of carbohydrate (4 kcal). It is thus easy to understand that lipid intake must be limited during a restrictive diet aiming to reduce fat mass. In addition, the body’s lipid stores are always abundant, even in athletes with a low fat mass. Scientific studies recommend reducing the proportion of lipids in the diet from 30–35% to 20% of total daily calorie intake. You should never completely omit them from the diet, however, as some lipids play a structural role and are involved in the synthesis of antibodies and some hormones; in particular, make sure you still regularly consume some high-quality fats (rapeseed oil, olive oil) and oily fish (salmon, tuna, mackerel, etc.).

  • Cut out alcohol. Alcohol in itself is a considerable source of energy, since ethanol has an energy density of 7.1 kcal.g−1 (against only 4 kcal.g−1 for carbohydrates and proteins). Therefore, consuming alcohol is likely to increase an athlete’s total energy intake (see Fact sheet No. 13 Effects of alcohol, p. 381). Alcohol also has indirect effects on the metabolism, reducing fat oxidation, favouring an increase in adipocyte size, and increasing the triglyceride concentration in blood. Thus, drinking alcohol promotes a positive lipid balance and, as a consequence, increases fat mass in the medium term, especially in the area surrounding the abdominal muscles. In addition, alcohol is often consumed at the same time as fatty and sweet foods, which only reinforces its deleterious effects on body composition and weight. Alcohol consumption should be limited for all athletes who wish to maintain a stable body mass.

How do the speed at which we eat and meal frequency influence weight loss?

4Some studies have shown that the speed at which a meal is eaten influences how rapidly we feel hungry again and what we eat in the following hours. 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 especially important during restrictive diets, when the urge to eat is often stronger. Other studies indicate that dividing food intake into five or six portions during the day stimulates the metabolism, while also decreasing hunger pangs and between-meal eating, as well as favouring controlled glycaemia and insulin production. Even though these results have not yet been confirmed in athletes following a restrictive diet, they suggest that during a weight-reduction diet it would be good to divide food intake throughout the day, planning a few snacks rather than concentrating all food intake during the three traditional meals. Finally, these results indicate that it is not wise to skip breakfast to accelerate weight reduction.

How fast is it recommended that we lose weight using a controlled diet?

5Some studies indicate that weight reduction should be limited to about 0.5 to 1 kg per week (about 1 to 1.5% of body weight) to maximize fat mass reduction. It does not appear to be advantageous to lose weight faster as any additional weight loss would be caused by chronic dehydration and major nutritional deficiencies, which significantly decrease training capacity and reduce muscle mass. This result was recently confirmed in a study comparing the effect of rapid loss of 5 kg (in five weeks) to a slower slimming strategy (in 12 weeks). For both groups, a weekly bodybuilding session was scheduled to limit the risks of muscle atrophy. The results indicated that athletes in the “slow loss” group decreased their fat mass more that the individuals in the “rapid group”, and that athletes in the “slow loss” group also increased their muscle mass. Therefore, athletes should anticipate weight loss to avoid decreased performance levels. These data also suggest that, in sports where weight is a criterion of performance, weight variations should be limited throughout the season.

What are the risks, for the athlete, of constantly restricting calorie intake?

6Although it is normal to control weight in various sporting disciplines and to use restrictive diets to reduce weight when it considerably exceeds the optimal weight for a given activity, athletes must keep in mind that these practices must be monitored. Several epidemiological studies have indicated that practising sports at a high level is often associated with eating disorders. In this context, it is important to supervise restrictive diets implemented by athletes to make sure they are not too drastic or prolonged. Indeed, excessive chronic calorie restrictions (total daily energy intake of less than 2000 kcal) jeopardize the athlete’s health (see Fact sheet No. 7 Eating disorders, p. 307).

Practical applications

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1. Increase the quality of food intake

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2. Modify the amount of food you eat

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3. Losing weight: first strategy

Composition of breakfast

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Composition of lunch and dinner

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Food choices

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4. If not enough weight is lost: second strategy

The second strategy is based on the same elements as the first strategy. Only the food distribution changes: breakfast and dinner are both divided in two. Image 10000000000000210000001FAB5C1627.jpg Use an appropriate hydration plan.

Distribution of meals during the day

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Poached cod fillet with herbs, Mediterranean vegetable gratin

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Photo credit: Thibaut Ruggeri.

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7Serves 2

8Preparation time: 30 minutes

9Cooking time: 45 minutes

Difficulty: Image 10000000000000510000001F750C032B.jpg

10Vegetable gratin

11 2 medium-sized tomatoes

12 1 mild onion

13 1 green courgette

14 1 yellow courgette

15 1 purple aubergine

16 1 crushed clove of garlic

17 10 g olive oil

18Fresh thyme

19 Salt, pepper

20Preheat the oven to 180 °C.

21Wash the vegetables and slice them finely.

22Lay out the vegetable slices, alternating tomato, onion, courgette, aubergine in an overproof dish. Make sure they are firmly packed in.

23Drizzle with some olive oil and top with the crushed garlic and thyme leaves.

24Season lightly.

25Bake in the oven for 40 minutes.


27 2 cod fillets with skin (140 g each)

28 1 star anise

29 1 bay leaf

30 1 sprig of thyme

31 15 g coarse salt

32Remove the bones from the cod. Keep the fish in the fridge.

33Heat 1 litre of water in a saucepan. Add the star anise, the bay leaf, the sprig of thyme and the coarse salt. Let the flavour develop for a few minutes, simmering gently.

34Plunge the cod fillets in the simmering infusion for 8 minutes.



37 5 g basil leaves

38 10 g dill

39 10 g chervil

40 5 g chives

41 5 g rapeseed oil

42 5 g walnut oil

43 10 g black olives

44Put the vegetable gratin on a plate.

45Arrange the skinless cod on top with the seasoned herb salad and the olives.

46Chef’s note

47This dish only provides 45 Cal for every 100 g, which is a low energy density (number of calories for 100 g). It is rich in proteins, which are necessary to prevent muscle mass reduction during a weightloss period. It is also a good source of vitamins and minerals (vitamins B, vitamin C, vitamin E, iodine, potassium, magnesium). To balance the low carbohydrate content, you can serve this dish with a few slices of wholemeal bread or wholegrain bread, and finish with a piece of fruit.

48Nutritional analysis per person

Energy (Cal)

Carbs (g)



Lipids (g)

Protein (g)




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