Ken, congratulations. I think that the heat had more to do with it than even the weight (though the weight was likely a factor). My nephew is a marathoner and loves the cooler temps. Lincoln Marathon 2014 with cool temps he ran a 3:29, and a year later with too warm temps he ran a 3:39 even though his training runs (in cooler temps) had him coming in thinking he'd run a much faster pace. Likewise the winner went from 2:17 to 2:27 from 2014 to 2015 with the warmer temps.

Pat yourself on the back for the hard work and the hard race!