The weight loss is an individual reaction caused by your environment (are you running around a lot or blobbing out?), your own physique and how much / how long you breastfeed for.
Loss of body tone, brest tone etc is actually caused by your being pregnant - no going back once the hormones kick in.
The big danger - and I speak from experience - is that when you breastfeed you are a calorie-burning machine, but when you stop you remain a hungry hungry hippo and end up looking like one.