Lacour-narural or not?
Ahhh, a stumpy Dubliner. Wink I'm from Newfoundland, Canada, so I'm quite familiar with things Irish.
Really thick people are outliers on the upper end of the regression because the regression is based on lean competitive bodybuiders who tend to be very mesomorphic. But even then they seem to be a relatively fixed percentage above a more mesomorphic lifter.
Just as an example of how much lean body mass (LBM) can differ when bodybuilders drop down into the single-digit bodyfat levels for contests, here's U.K. bodybuilder John Berry's stats as he got ready for the BNBF Central Championships (I'm using these stats because they're readily available on the 'net)...
Assuming he has an average skeletal structure for his height of 5'5.5", John Berry's lean body mass should be 153.3 to 157.5 lbs, depending on his exact joint circumferences.
On 1/04/06 Berry weighed 176 lbs at 11% b.f. --> LBM = 156.6 lbs
On 2/05/06 Berry weighed 167 lbs at 9% b.f. --> LBM = 152.0 lbs
On 3/06/06 Berry weighed 158.4 lbs at 6.9% b.f. --> LBM = 147.5 lbs
On 1/07/06 Berry weighed 151.8 lbs at 6.4% b.f. --> LBM = 142.1 lbs
His anticipated weight and body fat at the contest on 30/07/06 (assuming after carb loading and proper hydration) = 147.4 - 151.8 lbs at 5-5.5% --> LBM = 140.0 - 144.2 lbs
So Berry lost over 12 lbs of LBM in going from 11% to 5-6.5% b.f. At 11% he carried the LBM that would be predicted for his structure, but in "contest" shape he carried 12 lbs less LBM. Jon Harris, however, held his LBM right at the predicted maximum when he won the 2006 WNBF World Championship. So, in the off-season, Berry seems to have the raw muscle mass to compete at the world level, but he lost it in pre-contest phase. That ability to retain muscle when dropping bodyfat is probably the difference between regional champions and world champions. Of course, his muscle loss was also probably due to either an overly restrictive diet or a poorly designed pre-contest training program, or both. But it does illustrate that many drug-free bodybuilders seem to exceed the predicted LBM maximums during the "off-season" -- they may carry that LBM when they're "fatter" but they don't carry it as the contest approaches.
Using myself as an example. Right now, at ~16% bodyfat (as of this morning), I have about 1.5 lbs more LBM than my equation predicts as my maximum (after 15 years of very serious training). I'm in the process of going down to 6-8% bodyfat. When I get there it's a practical guarantee that I won't have that much LBM, and I don't have the long muscle bellies throughout every muscle group as do the more gifted mesomorphs. The last time I dieted down I was 3-7 lbs shy of that maximum (depending on hydration, time of day, etc.).
When I first formulated these equations I was a little disappointed that I was already very close to my maximums. But, realistically, after 18 total years of training, there isn't much muscle left to be gained by this drug-free body. Now it comes down to impoving weak points and overall symmetry.
I think you should definitely make the films. And diet down to the single-digits and track your lean body mass while you're doing it ...I need more data on heavy-set endomorphs. Smiley