Lean Mass Loss

Hi!

I've lost 5kg over the past five weeks or so, but the scales say that this is mostly lean mass loss rather than fat mass loss...could anyone explain why that's happening? I'm eating a balanced diet of around 1200 calories or slightly under, and I exercise every day. Most of the exercise is cardio, but I've also been doing strength exercises for my arms and I can feel and see muscle build up in my legs. Losing 5kg has put me back into the safe side of a healthy BMI, but I feel like it's useless if I'm not losing fat. So should I trust the scales or is there something I can do to lose the fat?

Thanks!