Obesity affects the heart by making it work harder and cause high blood presure. It can also cause diabetes and other heart diseases. Even a small weight loss (just 5-10 percent of your current weight) will help to lower your risk of developing those diseases.Today there is biomedical engineering. Biomedical engineering can make artificial, body parts to replace bad ones. You want to stay fit so you don't have to get these parts because these parts don't always work as good as the real ones.