What is a Japanese diet like for people living in Japan?

You are right that the food in Japanese restaurants is not exactly like what people eat at home. I rented a room to a Japanese student for a while. Most Japanese eat rice, with a bit of protein such as chicken or fish, and vegetables. The student would often fix a kind of "sushi bowl" for herself (and me)- rice seasoned with vinegar, small pieces of fish or chicken and some steamed vegetables, with soy sauce. The Japanese everyday diet usually doesn't include fried or greasy food, heavy sauces, or bread. You can certainly do that at home. But they eat small portions too- there's a saying in Japan that you should eat until you're 75% full. If you can do that, it would be good for your health and your figure. But most Americans are used to stuffing themselves until full. They also walk a lot more than we do. 

That's why Japanese people eat everything raw.  It's like a primitive man.