Remember not to run on an empty stomach before running. You must have some breakfast. You can choose some bread and milk, because running on an empty stomach is very effective in reducing fat, but at the same time it lacks carbohydrates and consumes a lot of protein, so the muscle content will decrease. You run today, and you consume both fat and muscle, but with less muscle, your metabolism will be slower. The fat lost today will grow back in just a few days, and the muscles will not be so simple.