Is it true or is it a myth?

Cheryll
Is it true that when your in a certain weight and  fat percentage it's easy for a woman to conceive? 
I'm 102 lbs, 5"2 skinny and very athletic. My family member keeps telling me that I should fatten myself up a little bit. That way it's easy to get pregnant. I don't know who to believe. Some people say it's true but others say  it's not. Any advice? :) Thank you ladies!