If I lose weight from not eating as much is it just muscle or did I also lose fat weight?

I have been drinking smoothies in the morning of just fruits and spinach, I have also cut back on how much I eat by a lot. I went from 156 to 137, The back fat I used to have its most definitely not there anymore but I also don’t know if i just lost muscle ? My stomach looks more flat that it did before and you can see my curves much better.