Is it common for breast milk fed babies to be chubbier?

If that is the case, then it does not apply to my baby. Haha... She is below 50% in weight and slim. But I don't see anything wrong with it. Neither did the pedia. She is very active and has been hitting her milestones. And I think genes may have a part to play. Both me and hubby are slim when we were babies and up to now.