You can eat oats with milk. If you eat not only this but also enough protein, you won't lose muscle. Oats can be said to be a kind of diet food, because the calories are relatively low, and because they are absorbed slowly, they are not easy to accumulate into fat, and they will feel full after a long time. If you eat oatmeal for fitness, because oatmeal is a kind of food with slow absorption and slow consumption, it can provide energy for muscles for a long time, without sudden increase of blood sugar, and muscles will not start to decompose because the body consumes too much energy, which has a good auxiliary effect on muscle recovery and will not reduce muscles. As long as you get enough protein and carbohydrates every day, you won't lose muscle.