Keto is an elimination diet. If you need it, it means you lack the gut microbes required to properly digest other foods.
Low-carb diets in general are good for a large number of autoimmune diseases, which almost unanimously relate to Rheumatism. The high-fat part of Keto is the dumb part, because most people with Rheumatism can’t get enough exercise to elevate to a higher metabolism to make that beneficial.
The ‘high fat’ part is a bit of a misnomer when it comes to the ketogenic diet/lifestyle.
Basically, all the diet entails is eating a limited number of carbohydrates to force ketosis, and ideally eating a sufficient level of protein (based on lean body mass and activity levels).
The balance of one’s diet is then made up of fats, which depending on goals (caloric deficit for weight loss etc.).
DO NOT START KETO WITHOUT FIRST CONSULTING WITH YOUR DOCTOR!!!