As best as I can tell, it takes ~2.5 calories to maintain a pound of fat for a day.  As far as I can remember, my brother has been 300lbs for the past 5 years, and slowly grew into that over the 7-10 years previous, So let's say in 2004 he weighed 160 pounds, gained 20 pounds a year until 300 pounds, then 15 pounds each year for 5 years (for sake of argument he gains all the weight on the first of the year).    Year Weight Excess Weight Extra Calories (day) Extra Calories (year) Extra Calories (total)     2005 180 20 50 18,250 18,250   2006 200 40 100 36,500 54,750   2007 220 60 150 54,750 109,500   2008 240 80 200 73,000 182,500   2009 260 100 250 91,250 273,750   2010 280 120 300 109,500 383,250    2011 300 140 350 127,750 511,000   2012 315 155 387.5 141,437.5 652,437.5    2013 330 170 425 155,125 807,562.5   2014 345 185 462.5 168,812.5 976,375    2015 360 200 500 182,500 1,158,875   2016 375 215 537.5 196,187.5 1,355,062.5     So it's taken an accumulated ~1,355,062.5 Calories to maintain his weight in the past 12 years.