Come on, your NHS is probably as badly run than my Sécurité Sociale, and allergic to consider better alternatives if it's not big pharma approved.
For the record I tried fasting for 2 weeks and it didn't do anything for me (I don't have dimorphism though). However we need scientific studies to either prove or disprove the benefits of fasting so we don't have to debate on just opinions but facts.
So that NHS has two options:
1) put someone through a fast. (Cheap - about £1000 per week). Then provide some talking therapy for some time.
2) amputating a leg. (Just the amputation is going to be between £8,000 and £16,000), followed by considerable physiotherapy and prosthetic legs.
Here the NHS wants the cheapest effective option, not the more expensive option.
If starvation works you should probably send the evidence to NICE.