Hello, Runner – All the writers on Intermittant Fasting that I have read say it is not suitable for teenagers. One of the reasons for that, I believe, is that the sudden reduction in calories on the fasting days is a deliberately imposed stress on the body, meant to alter the output of various hormones, including a reduction in a particular growth hormone IGF-1 (Insulin-like Growth Factor 1). To quote from ‘The Fast Diet’: “IGF-1, as its name implies, has growth-promoting effects on almost every cell in your body. It keeps your body constantly active. You need adequate levels of IGF-1 and other growth factors when you are young and growing, but high levels in later life appear to lead to accelerated ageing and cancer.”
One only has to compare one’s physical and mental development as a fifteen-year- old to how one was when aged twenty, say, to see there is still a lot of development due in any teenager and much of that is due to hormonal changes. Adolescence is tough enough as it is, I think, without deliberately imposing further physical stresses.
With your input, eating regular, healthy meals – but not snacking between them – would be a better choice for your daughter right now, rather than fasting, I would reckon, but that may be a big ask, at this stage of her life – I well remember thinking that my parents were old fools and knew nothing when I was aged sixteen, much to my shame when I looked back aged 24! Hopefully, as she grows up she will make her own good choices.

Hmmm – This may be an unpopular opinion but to be honest, I remember being a podgy 15 year old (exercise and eating healthily never helped me and I was a mess of pretty nasty hormones too) and I think if I’d started this lifestyle then I could have avoided a lot of very self-esteem sapping life experience. I understand the arguments against but I think everyone is different and that if your daughter actually WANTS to do it, you are happy to take the responsibility of monitoring her and you think she could cope with the hunger pangs etc. then why not?

I remember kids doing ‘sponsored fasts’ (proper ones with NO calories at all) for Comic Relief etc. when I was a kid and I don’t remember any of them slipping into anorexia. I doubt it would hurt your daughter, as long as you feel she has the maturity to understand that it’s not just a quick fix and she understands that she shouldn’t push it any further than you say and as long as you’re able to monitor how she is doing. I also think you should maybe stick to 6:1, rather than the full on 5:2 for her(at least to start with) and see how she gets on.

Are you sure that they need fasting? I think it is bad for kids.