Many studies show that the refeeding periods are important to keep resting energy expenditure levels “active” and avoid some of the adaptations linked to most usual diets. Therefore the weight loss may be more effective, although most of the studies have been performed in obese/overweight people and not in athletes.
Athletes are individuals with high levels of physical activity and energy requirements, and they may like to reduce body weight in order to improve performance. Their approach to dieting should be careful to avoid unwanted effects on performance or health. A moderate strategy should involve weight losses of 0.5-1% of body weight per week (a maximum of 35% restriction in daily needs).
Intermittent dieting may be an alternative way of reducing energy intake while avoiding compensatory effects of long diets, as mentioned previously, although its effects on athletes have not been extensively studied.
Individuals with high protein diet (30% energy intake) had lower energy intake than those using a lower protein diet (15% energy intake), because of the satiating effects of proteins. Additionally high protein diets maintained muscles growth and restoration, while reducing fat free mass losses associated with diet. In resistance athletes a protein intake of 2-3g of proteins per kg of body weight maintained the fat free mass, while only 1g was insufficient.
Although it is usually assumed that a low level of carbohydrates is good for losing weight, a recent meta-analysis has shown that they low carbohydrates diets are not more efficient than low fat diets.
Carbohydrates are a versatile source of energy that can be used for aerobic or anaerobic activities, with more efficiency than fat. A lower availability, because an emptying of glycogen stores or reduced blood glucose levels can affect performance, muscle fatigue and effort perception. It is usually recommended a quantity of 6-10g of carbohydrates per kg of weight per day for endurance athletes.
The key factors in losing weight seem to be the amounts of energy and proteins in the diet. During energy restriction stages it may be difficult to keep then energy intake low while maintaining carbohydrates and proteins ingestion at adequate levels.
During intermittent dieting it looks like carbohydrates should be preferentially chosen during the refeeding periods over proteins or fat.
A series of final recommendations:
- Avoid fast weight loss and severe intermittent dieting to maintain fat free mass levels.
- Combine resistance exercise with the diet, as it attenuates free mass loss and improve fat loss efficiency, while maintaining resting energy expenditure.
- Maintain a high protein intake during the energy restriction, and increase the carbohydrates during the refeeding periods
- Although there is no much information about the duration of each phase during intermittent dieting, for athletes would be reasonable to intercalate 2 weeks of energy restriction with 2 weeks of normal energy intake, which should coincide with the higher training volumes or better outcomes.
Intermittent Dieting: Theoretical Considerations for the Athlete.
Peos JJ, Norton LE, Helms ER, Galpin AJ, Fournier P.
Sports (Basel). 2019 Jan 16;7(1). pii: E22. doi: 10.3390/sports7010022.