Low carb diets
There are lots of these diets in slightly varied forms. Atkins is the big one, also Nerys and India's pig2twig diet, South Beach diet, and many more. These diets allow you to eat plenty of protein and even quite a lot of fat, but no carbs. So no bread, pasta, rice or potatoes. Even many fruits are off limits.
If you love fry-ups, steaks, meats with creamy sauces then this is the diet for you. The good news is that gin has no carbs; the bad news is that beer is loaded with them. Also, you will probably find yourself constipated and withbad breath. It is particularly good for people with diabetes and polycystic ovary syndrome (PCOS) because it keeps your blood sugar levels low. Even though you are allowed butter and cream it doesn't send your cholesterol through the roof as long as you stick to the rules. It can have dramatic results for some people, and there are many celebrity fans.