Question: are there any proven negative consequences from intermittent fasting? I've been doing it for two years and I went from 20 to 10 per cent body fat, working out, too, of course. My goal is seven per cent body fat. I have a cheat day every Sunday and then I fast all Monday, so I go around 30+ hours without eating, weekly. Could this by unhealthy in the long term? – JN
Answer: intermittent fasting – occasionally not eating for up to 24 hours – isn’t harmful as long as you’re healthy. (If you have diabetes or other health issues, talk to your doctor first.) On the other hand, there isn’t anything especially beneficial beyond its simplicity and convenience, says nutritionist Alan Aragon.
“The thing that worries me about this question is the goal of hitting seven per cent body fat. This is the leanness level of elite professional and Olympic-level boxers, sprinters and wrestlers. This is simply not sustainable on a permanent basis unless you have been blessed with a greyhound's metabolism or you’re engaged in athletic competition at the elite or professional level.”
So while intermittent fasting might help you hit the seven per cent body-fat mark, don't expect to maintain it – at least by means that are remotely healthy. “Even 10 per cent body fat for the vast majority of guys is a highly athletic body composition to maintain,” says Aragon. “There's nothing special about intermittent fasting that will push things further. Sustaining a kilojoule deficit by whatever means is what causes fat loss.”