Fats?

I think what you mean is to eat proteins with your meal. Good protein in your meal will make you feel fuller longer and helps in the digestion of foods that you have eaten.

I hope this answers your question, if not please be a little more specific in your question or provide the link to the item you are referring to.

Good luck and best wishes. 

TipTopManager is correct. Eating more proteins actually fills you up faster so that ideally, you won't eat as much during a meal.

Good answers have been given but there is something they haven't addressed. Eating fat does slow down digestion. It causes the other foods to take longer to digest. This doesn't mean of course that you should eat fat before your meal and perhaps this isn't what they mean but I just wanted to let you know for common knowledge.