Weight loss will help your joints and likely your back. I just reviewed a study that started with increases in hip and knee replacements. They were asking why. They suggested it was North American’s extra weight. People are heavier than their parents and grandparents.
The personal trainer who talks on our local radio show definitely says counting calories and what you eat are more effective than exercise for weight loss. In his view, the exercise tightens, but isn’t the main weight loss tool.