Training while fasted

Several years ago, The Warrior Diet became trendy for athletes, mostly because it was a diet (lame) that had the word “warrior” (cool) in the title. The diet was proposed in a book that subsequently got a lot of coverage in a now-defunct magazine that featured the author as the senior editor (Mind and Muscle Power was the name, and it featured the founders of T-mag/T-nation as the primary staff). Although The Warrior Diet (eating a big meal or two in the evening, basically, but fasting for the rest of the day) has become part of the lexicon of many trainers and athletes, not many of them still use it.  Intermittent fasting, which is somewhat similar, has recently become popular with athletes in various sports, although in both cases research is scarce. Or is it?

Athletes have been eating only at night and fasting for the rest of the day over the past few centuries, for at least one month out of the year. Obviously we’re talking about Muslim athletes here, who fast during the month of Ramadan – which begins in a few days. Whether it’s intermittent fasting, Warrior Diet, or whatever, the research on Muslim athletes during Ramadan offers substantial guidelines and caveats for training in these various states of fasting:

1. Evidence from sound research supports the conclusion that athletes are unlikely to suffer any substantial performance decreases as long as they maintain their total energy and macronutrient intake, training load, body composition, sleep length, and sleep quality.
2. The optimal time to conduct a high intensity training session is in the evening, after breaking fast.
3. Multiple training sessions or competitions will be impaired if adequate hydration is not allowed.
4. Performance requiring sustained rapid responses are better in the morning and decline in the late afternoon, during days of evening-broken fasting.
5. Middle distance runners should reduce workload during Ramadan.
6. During fasting, increased gluconeogenesis and/or a reduced intake of protein could lead to a decrease of lean tissue  and adverse effects on muscular performance, while lack of immediate protein ingestion could compromise responses to strength training.
7. Fasting  can adversely effect body composition and agility in women.
8. Repeated daily fasting followed by refeeding can result in increased reliance upon lipid oxidation at rest and during exercise and an increased capacity of the skeletal muscle and liver to store carbohydrate.
9.  Cardiac (heart rate) and ventilatory responses to moderately intense bouts of sub-maximal aerobic exercise (70% of VO2 max) are slightly (<5%) but significantly (P<0.05) reduced during Ramadan fasting.
10. In soccer players, observing the fast resulted in reduced performance.
11. In male rugby players, observing the fast resulted in increased lipid oxidation.
12. Reduced sprint speeds were seen as a result of fasting during Ramadan.