A ketogenic diet is when you are basically eating no carbohydrates and very little protein and thus, the majority of your calories is from FAT.
After about 3 days of not having any carbohydrates in your diet, your body will run out of “glucose” and will then start using KETONES as fuel.
Now, this is a good way to burn fat for many people because without carbs and glucose, your blood sugar and insulin production will be low and your food will have a harder time being converted to body fat.
However, this is NOT a good way to gain muscle. In fact, long-term ketogenic diets will actually cause muscle loss.
If you’re going to follow a ketogenic diet to lose weight, yet you still want to build muscle - you’ll have to cycle it carefully and not do it long-term. No more than 2 weeks of ketosis and I actually prefer something like 7 days on, 3 days off.
And if you want to lose fat and still build muscle at the same time, you can watch a great video about this topic and how you can quickly turn ON your “fat-burning genes”.