The Best Answer
If you're already fairly lean (under 16 percent for women and 10-12 percent for men), then it's okay to work on building muscle while minimizing fat gain. When you're leaner, your body will put on more muscle than fat (provided you eat correctly). However, if your body fat is higher than the above, it's best to get leaner first so your body won't put on more fat when trying to put on the muscle. Men with 15 percent body fat or higher that try to gain muscle end up putting on a lot more fat since insulin resistance is higher the more body fat you contain.
I personally started by loosing fat even though I'm a pretty skinny dude. I had a little tire around my waist that I wanted to get rid of. Once I did that along with some Kettle Bell swings and situps for a few weeks, I felt as though I had built a strong core and I was really confident and excited to start building muscle.
I've been doing Geek To Freak for about 2 weeks and am getting similar results - meaning I'm putting on muscle. I'm a bit more confident in G2F because the other diet and workout went so well. If I had the confidence I have now, then, I probably would have started with Geek to Freak.
Let me shorten that for you. If I could do it again I'd probably start with building muscle then loosing fat, but if you don't have a strong core yet think about starting with a the slow carb diet and some kettle bells.
Teorethically, it would be better to build muscle first, since more lean muscle means a higher basal metabolic rate, making the job easier later.
What I did was lose about 30 pounds first, and then add muscle, because the results get more visible quicker, and you can stay motivated more easily.
So, you should choose between both.
While it's possible to just burn pure fat, you will probably burn muscle too. Similarly, you won't ever put on pure muscle, you'll gain a little fat with it. Before you guys reply and tell me this is incorrect, at least agree with me that this is true for the average person who is not very very high or very very low in body fat.
I have tried both before and I think the way to go is lose fat first and then slowly put on muscle. The increased metabolism you'll get from increased muscle mass is HIGHLY overstated.
Join the 4 Hour Body Superhumans!