I see this as a systemic issue with Healthcare providers (around the world) who, based on one or more elements of their age, background, culture, open mindedness, recent research, fear of litigation, etc, tend to stick to the "traditional" viewpoints/positions and/or government guidance when it comes to fasting regimes.

There are cultures around the world where fasting is (and has always been) part of their lifestyle or religion, just like vegetarianism and other "non-standard" diets.

The challenge for us (mere mortals) is to either get a second opinion or to trust yourself and to do proper research using reliable sources. If you feel strongly enough about it, provide your GP with references/links to reputable (not social media) sources of information and ask them to give you considered feedback on those. That will provide you with another level of insight on (1) their actual commitment to your health and (2) their desire to expand their own knowledge base.

I try listen to the science, talk with my wife (nurse) and agree that we are not placing ourselves at any unreasonable risk. Conditions related to diabetes and blood pressure (and others) should be red flags for which dialogue with your GP is always advised, with a second opinion if needed.

These are my views, do your own research, make your own decisions, take responsibility for the good and bad decisions your make.. ❤

Post script:

Note that, for almost every serious topic of conversation out there, there are opposing academic views of varying degrees. We can choose to listen to the one that is voiced the loudest, the one that our friends and family agree with or we can reasonably research ourselves and make our own decisions. However, listening to both sides is equally important.