Running depends on the specific situation. If you do explosive training in sprint, your leg muscles will increase. If the speed is constant in long-distance running, your leg muscles will not increase so obviously, or even weaken. You can build large muscles mainly through anaerobic training. If you lose fat and do more aerobic training, your muscles will not increase significantly, and your dimensions will not increase so easily. Losing weight on an empty stomach is definitely not acceptable. To lose weight, we must control it through exercise and reasonable diet. Try to eat less greasy food and high carbohydrate food, and eat more foods and fruits with high crude fiber. This is the scientific way to lose weight.