Hi, I'm 28 years old, 5ft 8" and currently weight 13st (182lbs). I've been using a mix of dieting/healthy eating and training over the past 2 months and have seen great results, I was 15st 7lbs (217lbs) when i started. My BMI for my height suggests my ideal weight is 10st (140lbs) or there abouts though i'm not sure i'll ever get that low, while BMI is a handy tool to have it ignores to many factors to be entirely accurate and thus i can't use it as a definite goal. I was aiming for around 11.5st/12st (161/168lbs) as my ideal goal but thats where the advice i need comes in!

Basically, i've changed my excersize routine to involve a lot more weight lifting as apose to just fat burning jogging/running/crosstraining. with the goal of eventually replacing my man boobs with chest muscle and gaining strength where i've lost weight. (I practice Ju Jitsu at a local club and during some excersizes i've already noticed the loss of my 2.5st (35lbs) that i had behind me.) I decided to use an off-the-shelf brand of protine shakes to help with this, i don't have the brand name to hand, and i've not yet looked into the science of balancing the protine with my workout. The issue i have, is that i'm in a position now where i feel i need to start building the muscle specifically in my chest as i'm afraid my skin (which was stretched to reach my heaviest weight) won't return perfectly, and so i'm keen to start using the shakes and training harder, however, i'm concerned that its too early to be using any sort of "Mass Building" shake and that my weight loss will be stopped/reversed by the effects of the shake.

I still have a little bit of a tummy, though nothing compared to when i started this project, and i have no idea how these shakes will affect that. so basically i'm looking for advice on when is the best time to transition between pure fat burning excersizes and muscle building ones, should i reach my ideal weight (11.5st/12st-161/168lbs) before starting to build muscle, or should i begin now and hope that i continue to lose my belly?

thanks in advance for any help you can offer!
and sorry if this thread is in the wrong place, i'm new :S
Huw