You might enjoy reading The Art and Science of Low Carbohydrate performance by New Atkins co-authors, Steve Phinney and Jeff Volek. Both are athletes (Phinney is an MD and Volek is an exercise physiologist), and the information is aimed specifically at athletes eating low carb. You are likely to experience a period of keto-adaptation lasting 2-6 weeks where glycogen is depleted and you may not have the full energy you need to perform at your best. Once you get through that period, you will be able to access 10x+ as many calories in the form of stored body fat as you were able to access in the form of glycogen when you were eating more carbs. There will be a period of adjustment, to be sure, but it will pay off in the end in the form of improved endurance.