I enjoyed reading the diary by Blue Heron on the myth of Big 10 size (http://mgoblog.com/diaries/myth-big-10-size) A comment in the diary by CRex on body fat mass per conference got me thinking. While that level of data would probably be hard to compile, we can be reasonably sure that under Barwis, fat has decreased and muscle mass has increased.
According to The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 56:B191-B197 (2001), muscle is almost 20% denser than fat. If, in fact, Michigan lineman, both on offense and defense, have decreased fat content and increased muscle mass, say by 5%, I think that our lineman could appear smaller, but actually weigh the same as a lineman who had higher fat content.
This also doesn't account for changes in strength, agility, endurance, and stamina. I believe that both at the end of games and the end of the season, superior conditioning will weigh heavily in Michigan's favor.
I remember attending the 2004 Rose Bowl, and being struck by how our linemen were often winded, with their hands on their hips, manhandled by USC. I am so glad that under Barwis, we can look forward to Michigan playing hard and keeping up with any opponent they face.