When it comes to losing weight, keeping it off in the long term, maintaining a healthy lifestyle and living a long life then we are all experts. The thing is we may all be experts but we cannot all be right. Winning the argument on here doesn't make you right particularly when you can get shut down by someone who doesn't agree with you, leaving the floor open so to speak.
So if you are very slim, very fit, take no medications and are very healthy with no aches or pain or diseases or medical conditions of any sort then you might have a handle on a lifestyle which is worthy of serious consideration. A keto diet with IF and regular exercise ticks all the boxes for me. The key is metabolic health and concerns a hormone called insulin.
I mean it's a complex issue but we can in theory benchmark various approaches in terms of uncontroversial objective metrics, such as:
1. Do practitioners achieve healthy weight and manage to keep it off long term?
2. Do practitioners enjoy optimal long term cardiovascular health? (Atkins, keto, paleo et al likely fail this sanity check)
3. What is the impact of the diet on the expected life span of practitioners? (ditto, as a consequence of 2. )
In practice, the body of rigorous research data regarding many diets is lacking, posing a risk to adopters.