okay i don't understand how when girls loose weight they loose their boobs and butt aswell. How is that Victoria's Secret models are extremely thin but have full breasts?

Well they're probably fake. Don't try to look like them. They're freaks of nature and I mean that in the nicest way possible. Boobs and butts are fat so it makes sense that you'll lose them as you lose weight. I've come to the conclusion that you just have to decide whether you want big boobs and butt or a stick thin figure.There are certain ways you can work out to avoid losing your boobs and butt but I don't know what they are. Ask a personal trainer!

they get implants!!!!

Some women are just born will fuller breasts, myself included. I'm 5Ə'' and I've gotten my weight down to below 110 before all the while, I was still a good-sized B-cup.
It's possible to keep some weight on your chest even while losing weight by doing chest exercises.