It was life-changing. I lost 22kg in two months, with no exercise. I am now back to a healthy BMI, but I no longer use BMI as a measure, I use the Relative Fat Mass Index (RFM) because my research indicates that this is a more accurate measure for tall people (I'm 6'3").
Besides looking great after shedding all that weight, I never expected the mental benefits to be so pronounced. Indeed it is fair to say it has had a nootropic effect. I no longer 'need' coffee, and the persistent brain fog has lifted and my default state is calm mental clarity.
Of course, I can only speak from my own personal experience here... I haven't done extensive blood tests pre and post this lifestyle change, but the change has been so shocking that friends and family cannot believe it.
You might think going 16 hours with no food is going to be hard but if you get the timings right, it's easy (and you get used to it). I start my fast at 8 pm, and I break the fast at noon. This way I can have business lunches and early-ish business dinners (as long as I finish eating by 8 pm). Most restaurants cater for vegans or at least have a vegetarian option. If not, I go for a fish option.
When I break the fast I do it with an avocado/cucumber/kale/spinach smoothie which blasts my body with super nutrients. I avoid all processed carbs (no bread or pasta), I avoid all processed sugar (no cola or any refined sugar products), I avoid all dairy, and of course, avoid meat. Also, there is no calorie reduction... I eat as much as I like in my 8-hour feeding window (which controls Ghrelin and therefore doesn't mess up my metabolism).
Always consult a medical professional before you do any drastic changes like what I've done, and do your own research on this stuff so you have the confidence that it's the right choice for you, and that you'll stick with it.