First, great job on changing your life and getting more healthy and active.

One thing though, you do not necessarily need to "lift heavy" to be active.

As a matter of fact, most people--most but not all--will actually build more muscle by doing a 4x12 routine--this is 4 sets of 12 reps per set, the catch here is that you only rest about 30 seconds between sets.

Only increase the weight you use when you can do all four sets without needing to use every ounce of strength you have to get them.

This method, will help you build muscle--which is great, because the more muscle you have, the more calories you burn even at rest.

But, because you are not resting much between sets--you get some cardio as well--not bad.

Hope t his helps.