There are many weight loss tips that come and go. That's because many of them are trendy diets or just fad. But these 11 pieces of diet advice are sound and more grounded in research, so they are timeless.

There are many weight loss tips that come and go. That's because many of them are trendy diets or just fad. But these 11 pieces of diet advice are sound and more grounded in research, so they are timeless.