People say there is no guarantee. That is not entirely true. When you change your thinking, everything else changes, including the way you look and feel. And that is something you do have control over.
Yet more people will invest more energy on a horse race or the stock market. I am not saying don't take chances. I understand that the end results could be substantial returns. However, with weight-loss and fitness you are investing in yourself. And you can envision the end results.
While you may not be quite sure how the stock market will behave or if the horse will make it, you know that when begin investing in your health and fitness,there is a guaranteed payoff. And it is tremendous.
It seems to make more sense to invest the most time and energy in the things you can control. And certainly if you don't believe in yourself---than who?