The picture is pretty surprising and gives insight into obesity. You may notice that the skeletons are roughly the same size. Believe it or not, our skeletons do not gain or lose very much mass depending on our weight. You might also notice that the muscle mass even though slightly larger on the obese subject is roughly the same size as that of the average person. The bulk of the size difference is adipose tissue or fat. The digestive system of the obese subject is more than twice the size of the normal subject’s. The same is true for the heart. Pumping so much extra blood to feed the 100 lbs of excess fat tissue and enlarged digestive system puts a real strain on the heart and can lead to many problems.