Hi boggey79, I sympathize with your frustration as I'm sure we all do!
The topic of how appropriate 5:2 is for those of normal weight has cropped up a number of times. I think we could do with pulling together (in an FAQ?) the information about the mooted health benefits of 5:2 - apart from the (substantial) health benefits of weight loss for the overweight. There is a danger (in my opinion) that the overwhelming interest here in weight loss might lead some visitors to conclude that the forum or - worse - the intermittent fasting lifestyle is not for them.
It would also give an educational opportunity ('ammunition') to anyone like boggey79 who is faced with a doctor who knows little or nothing about the matter but looks over her (or his) half-moon spectacles and says knowingly: 'take it from me, this is a dangerous fad'.
As I see it there are 3 potential wins for intermittent fasting (including 5:2) quite apart from any weight loss. They might each be considered as speculative, probable or proven, I'm not sure. I'm very open to correction and addition here, I'm trying to get it clear in my own head!
- Autophagy - fasting gives the body 'repair time' to fix cellular disrepair which is otherwise missing in a typical Western diet. Spring cleaning for the body! Hence reduced risk of ailments relating to cellular disrepair (especially cancer, I suppose). See for instance http://onlinelibrary.wiley.com/doi/10.1196/annals.1396.020/abstract.
- Adaptive cellular stress - from the work of Dr Mark P Mattson with mice, the idea that fasting can make the brain regenerate cells and be protective against degenerative ailments (especially dementia, I suppose.)
- Lowered IGF-1 - insulin growth factor 1, a growth hormone mostly produced in the liver, is critical for growth in the young but associated with accelerated ageing and with cancer in mature adults. It is increasingly accepted (a/c to Wikipedia anyway!) that IGF-1 is not just a marker but a pathogen (=contributory cause) for both. Under the supervision of Dr Valter Longo, Dr Mosley found that an almost-total 3 day fast reduced his IGF-1 substantially, and later found that following his 5:2 regime also lowered it (and with less anguish!). Returning to an ordinary diet causes IGF-1 to return rapidly to its previous level.
There is in my mind something contradictory between the idea of 'repair time' when the body doesn't go for growth hell-for-leather, and - at the same time - cellular stress promoting cell regrowth. Can they both be right?
Re the IGF-1: is it fasting
per se that causes the IGF-1 reduction, or is it avoiding certain foods that trigger production of IGF-1? Maybe these foods get avoided in a fast almost 'by accident' unless one takes a disproportionate amount of them on a fast day. Obvious candidate: milk.