there have been so many fad diets that come in and manipulate people who don't know any better into buying their books, coming to their seminars, subscribing to their channels, whatever, but it always boils down to calories in vs. calories out. if you're getting the right amount of calories in for your work rate and size, then you'll feel good and get results, no matter what those calories consist of.

ketosis is a real thing, but the effectiveness of it is disputed. the reason paleo, keto and carnivore diets mostly work is they give you a variety of food that's a.) filling and b.) really fucking boring to binge on. you're not going to over eat when all you have is spinach and grilled chicken, you're going to force yourself to the amount of calories for that day and have an abundance of protein, but there's no trick into making your body work differently. suddenly switching out pastries and pasta to "healthy fats" and meat isn't gonna make your body say "shit, take this bloke's muffin top and make it fuel, stat". it's all down to how the diet makes you feel, and how you can manage your calories and macros when on that diet.