spreading of fast food in Japan

Recently, the number of fast food restaurants seems to increase in Japan. we can use those restaurants till night without circumstance. The very low price is also the attractive point. I live alone now, so I also eat fast food when I don't want to cook. I feel it's so convenient for busy people, but I concern the bad effect for our health. Those food have high calories, and can be the cause of serious fatness. Depending fast food is bad habit, i think...