Not that this isn't egregious... but it likely wasn't fat. It was probably water and a gallon of gatorade would have gotten him back to normal weight.
(not that it makes it ok... just sayin)
I actually think it is worse if the weight loss was all water.
15 pounds of water is 1.8 GALLONS.
His organs were shutting down and he was near death from dehydration. Not a pretty way to go.