Actually, running won't get thicker and thicker. Running increases leg muscles. Muscle needs much more energy to maintain metabolism than fat. The more muscles you have, the better your weight loss will be. One of the characteristics of muscles is that when you don't exercise, muscles will absorb themselves. Muscles don't exist in you forever. If you don't use muscles, they will be gone. Fat is just the opposite. Fat means that the less you use it, the fatter it will be. The purpose of running is to improve metabolic rate. Running is not only to exercise the leg muscles, but also to exercise the whole body muscles, and to achieve the purpose of consumption by increasing muscles.
In addition, don't just do one kind of exercise. Repeated individual exercises make muscles adapt. Lazy muscles. If you do an exercise repeatedly, this muscle will not grow. If your muscles are not stimulated, you won't grow. If you don't gain muscle, your spending power will decline, and it will be more difficult to achieve the goal of losing weight.
Aerobic exercise and anaerobic exercise should be practiced. The thickness of the leg is related to the weight. The heavier the legs, the thicker the legs. So it is possible to slim down your legs after losing weight. Take your time.