I don't post on here very often anymore but I'll give you my two sense. I have a dual degree in exercise science and exercise biology, so I'm on a different wave length than some tradition information out there. But here goes nothing...
From a biological standpoint, it would take special genetics to be able to gain muscle AND lose fat at the same time. It's not as "rare" as people make it out to be, there are variables that make it possible. Your thyroid is the key to it all in that sense. If you have a faster than normal thyroid, your not going to get fat no matter what you do. We all knew someone in college who could eat pizza and wings all day while downing Guinness and never put on an ounce. And having a fast thyroid isn't going to prevent you from putting on muscle size either because the caloiries, protein, and carbs are being digested, just at a faster pace.
You can put on lean muscle and lose fat at the same time over a longer period of time. Your not going to be able to "bulk" and "cut" at the same time in the sense that a bodybuilder does. But over the course of 6 months, you can put on 10 pounds of natural muscle and lose bf% at the same time without question.
But again, the majority of us don't have accelerated thyroids. Which leads to supplementation. Nature's genetics don't let all of us consume a ton of calories without consequence. But thas why we have supplements. With supplements, we can take in 300 grams of protein and stay under 2,500 calories in a day, which would be somewhat impossible without powders. Also, tyroid/metabolic enhancers like Cytomel (t3) or Synthroid (t4) can boost our metabolisms two fold. Can you put on 30 pounds of muscle in 16 weeks and lose fat? Probably not. But you can certainly put in 10 pounds of muscle in that time and do it.
On July 1st I was 240 with 15% body fat. That gives me approx 36 pounds of fat and 204 pounds of muscle, bone and tissue.
Today, Oct 15th, I'm 236 with 11%bf. That gives me 26 pounds of bf and 210 pounds of muscle, bone, tissue.
So statistically speaking, I lose 10 pounds of fat, and gained 6 pounds of muscle, with my weight only changing a matter of 4 pounds total. May not seem significant, but it really is. The reason why mopst people, natural or juiced, say you can't do this is ebcause whent hey talk about muscle gaine, they're talking about 30 pounds of muscle gain. And they say fat loss, they're saying 18% down to 5%. Those are extremes.
There's absoultely no evidence to support that you can't put on muscle and lose fat over a period of 3-4 months at the same time.
Lastly... most people when they talk abotu losing fat, they say "You have to burn more calories than you take in." Yes, but no. Calorie defecit is one way to lose fat, but its not the only way. Interval training and training with no carbs burns fat straight up. If you do cardio on an empty you will burn fat tissue straigt up, regardless of your calorie situation.
If your talking about putting on 30 pounds of muscle, sure you need to eat hella food. But if your talking about putting on a little bit of muscle while losing a few %'s of fat, you can do that without putting yourself in a calorie defecit.