IMHO 10% person would be able to eat cheat meals and then would be able to be more intense in the gym because he has more calories stored. IMHO in order to maintain 6% one cannot have an big excess calories stored or they would not be able to maintain that low bodyfat. In order to maintain the 6% one would have to cardio the extra calories instead of using them as energy in the weight room. Building muscle and being in an anabolic state has alot to do with calories eaten. Dorian Yates said ALL his major injuries came from DIETING and trying to maintain intensy in the gym. If one relaxes the diet , they can be more intense and build more muscle.
Anyway, If you're saying that you would not maintain the 6% and allow yourself to increase fat , then I agree. I disagree if you're saying one is encouraged to eat extra calories and still be able to maintain 6% There isn't that much of a difference in metabolism from one being 6% and 10%
I was around 6% the first 30 years of my life year around. However I was not eating the calories that I am now. So maintaining 6% was easy because I wasn't really eating. It wasn't because my metabolism was somehow through the roof. It was faster then it is now. But that is really a red herring. Anyway after 30, my metabolism did drop, my strength and size shot through the roof. The calories I could eat increased significantly, but so did bodyfat. The increase (in calories eaten) allowed me to be more intense in the gym.
3 cheat meals a week is about what I do now
ghrelin has been shown to assist fat loss. Leptin however ,has shows lipolysis increases in RODENT studies. Human studies have been done in infusing leptin inside a person with no change in fat loss... Probably due to leptin resistance
The role of leptin in human lipid and glucose metabolism: the effects of acute recombinant human leptin infusion in young healthy males
My experience and your experience are exactly opposite. When I was low bodyfat I really wasn't eating the calories I thought, even with a cheat meal here and there. It's basically the same advise I give people when they are hard gainers and want to bulk. Most of them are't eating what they think they are and hence not putting on weight. I don't think it's a significant metabolism difference , but an energy balance difference.
We are probably more close on our ideas than you think, with some minor differences. Your assumption is that I'm in a regular caloric defecit to maintain my bodyfat, which is far from the truth. I eat in a very big surplus on workout days with my defecit being on off days. This method combined with doing intermittent fasting works rather well for me. I have been around 4000 cals on workout days (+/- 500) and between 1800-2300 on off days. Despite still coming out with a weekly average surplus, I still manage a slow recomp. I will adjust those numbers up or down a little to go more for one goal or the other, but I am within about 500 cals of those numbers year round. Even during my final weeks of prep, my workout day cals stayed around 3500-4k (3 times per week). I can guarantee that my numbers are exactly what I eat as well and right on the money, since I weigh, measure, and track everything.
My metabolism is not exactly the fastest either, at 39 years old.
Most of my diet principles are my own variation of Martin Berkhan's Lean Gains protocol of IF. Here is his article on Leptins role and IF, and he touches on how implementing proper refeeds keeps you lean and fat loss continuing.
Intermittent Fasting, Set-Point and Leptin | Intermittent fasting diet for fat loss, muscle gain and health
As for the original subject, I know personally my training has never suffered from being lean....and I train fasted as well. A lot of people think their training will suffer if they don't eat before training, which is also a myth. There are studies that show fasted and fed training have no difference whatsoever on performance, and fasted training can actually be more favorable for the post workout anabolic response
http://www.leangains.com/2009/12/fasted-training-boosts-muscle-growth.html