Trying to lose weight with exercise and starting a keto diet at the same time can provide fast results for a "multiplier" effect. However, if you haven't exercised in more than 6 months, you should wait to start the keto eating plan. Begin an exercise program first so you are adapting to only one physical change at a time. After 2 weeks of working out 3-4 times per week, you should be ready to start the keto diet.
Your glycogen stores can still be refilled while on a ketogenic diet. A keto diet is an excellent way to build muscle, but protein intake is crucial here. It’s suggested that if you are looking to gain mass, you should be taking in about 1.0 – 1.2g protein per lean pound of body mass. Putting muscle on may be slower on a ketogenic diet, but that’s because your total body fat is not increasing as much.5Note that in the beginning of a ketogenic diet, both endurance athletes and obese individuals see a physical performance for the first week of transition.