Skeptical of "light" foods

With no data whatsoever, I reject the assertion that low-fat or sugar-free versions of foods truly help people lose weight or to be healthier. What I expect is actually effective is one or all of:

1. Exercising more


2. Eating different types of foods (cutting out the ice cream instead of switching to low-fat)


3. Just plain eating less

I suspect that people who lose weight while eating light foods are also doing at least one of the above, and that people who only eat light foods without doing any of the above see little change.