Losing weight without reducing performance

Karl Sudi 17. October 2018

Body weight is a performance-limiting factor in many sports. Particularly in the various endurance disciplines (for example, bike racing, mountain biking, Alpine marathon), a low body mass is often an advantage, especially if the athlete has an optimal body composition (ratio of muscle mass to body fat tissue).

So, how can you achieve a low body fat percentage without compromising your performance?

The "classic" way is often for athletes to change their diet and eat fewer calories and carbohydrates than they are used to and increase their training workload at the same time. This strategy is often successful in the short term and can lead to significant weight loss within just a few days. In the medium term, however, this way is rather counterproductive because the loss of body mass is mainly attributed to depleted glycogen stores, a loss of body fluids, and a breakdown of muscle mass. Athletes with a naturally low body fat percentage particularly lose relatively more muscle mass than athletes with a normal body fat percentage. This also reduces their performance, especially when it comes to more intensive training loads above the aerobic threshold. At the same time, there is often a significant reduction in the energy metabolism, which helps the athlete’s body fat percentage to start rising above the initial value after such a phase of weight loss when they start eating normally again.

Alternative ways include restricting your calorie intake, which can lead to a weight loss of up to 1 kilogramme a week. This is achieved by means of "intermittent fasting" whereby the athletes eat normally one day and reduce their calorie intake by up to a third the next. This way also works well with the "fuel for sport" approach, in which the diet and carbohydrate content take the respective training intensities into consideration. Thus, on those days that involve intensive and longer training units, the caloric intake and carbohydrate content are kept at a normal or high level. On those days that involve a low training load or regenerative training, the caloric intake (and carbohydrate content) is significantly lower. This strategy can be used in the medium and long term and leads to an optimised body composition and sport-specific performance. If you reduce the overall calorie intake, however, you need to make sure that you get enough nutrients, minerals and vitamins. To ensure the breakdown of muscle mass is as low as possible during a long-term calorie restriction regime, you need to make sure that your protein intake is sufficiently high. According to recent studies, the protein content should be significantly more than 2 g/kg body weight.



  1. Athletes should know their current body composition and be aware of how much the respective muscle mass and body fat percentage fluctuate in the different training phases. They can thus determine their own "optimal body composition" and use it to track the efficiency of the respective measures.
  2. The restriction of calories to reduce body mass and the body fat percentage should not be too radical, but rather geared towards the needs of the sport and training loads. The loss in body weight should not exceed 1 kg/week.
  3. Intermittent fasting is good in the medium and long term if you ensure that you get a sufficient supply of macro and micronutrients. Taking appropriate supplements can be of value during these phases.
  4. A sufficiently high protein intake helps to ensure that you achieve an optimal body composition and retain muscle mass.