Why do some breastfeeding moms still chubby/fat when ideally, they should be losing weight?

I think it depends on every metabolism. I have a pretty fast one and after lesa than 1 month I didn't have the belly and after 2 months I was back my previous weight. Now after 6 months I'm skinnier than before. (168cm 48 kg) maybe because I'm also tired, but don't think too much about it. We're feeding an human being 😍