thanks for the reply, I'm not sure if it's kinetic energy or inertia, I think they are both apply-able to this topic. More mass you would need more force to even begin to move, i.e; 250lb bald man... 100lbs of useless fat -dead weight- wont have enough muscle to physically move his body fast enough or hard enough to make the bike flip. BUT if a scrawny 5'3 skater dude weighing in at about 110lbs with 14lbs of fat won't have enough inertia to cause the bike to flip.
You require a level of weight that is substantially effective to move your bike, but with weight comes sloth.
Heavy Man + More Fat Than Muscle = NO FLIP
Heavy Man + More Muscle Than Fat = ILL FLIP
^ Formula for the 6' fat bald guy who currently is residing at his mom's basement