Yes, it's true. 4 or 5 days a week is sufficient. And if you want to lose weight, it might do you well to realize that weight loss is 80% about what we eat, 20% about exercise. Don't get me wrong, exercise is very beneficial, and it also keeps our bodies strong and toned. But all over-doing the exercise is going to do for you is to make you tired.
You might look into the ketogenic or atkins diet. Healthy ways to lose weight and great ways of eating for life. Info all over the internet.
Along with this, it's recommended to get at least 8 hours of sleep per night. Why? Because we do lose weight while we sleep, believe it or not.