Is it true that breastfeeding helps to loose weight easier after delivery? Must LO latch to consider or pumping breastmilk out is also the same?

It will certainly help but I know a mother who could not breastfeed at all (she was on medication) and her baby is fully formula fed. She lost weight really fast. Reckon it either had to do with the medication she took or the fact that she was very active. She's generally a gym freak so she was working out and going on her low carb, high protein diet as soon as the doctor gave her the green light.