The connection between fat and hormones is at the forefront of fat research. In the past, scientists assumed that the problems caused by excess fat were the result of its physical burden. They worried that fat would strain bones and joints, plug up arteries, and crush internal organs. But today, many scientists believe that the chemical contribution of fat is more important—and far more dangerous. Although the hormones that fat secretes are critically important in small doses, in large amounts they can trigger runaway inflammation, confuse other organs, and throw off your body’s regulatory processes.
Here’s an example: Osteoarthritis is a painful condition that causes the cartilage in your joints to break down. Studies find that as your body weight creeps up, your risk for osteoarthritis rises along with it. The traditional explanation is that excess weight causes extra wear and tear to important joints like your knees, which is certainly possible. However, increased body weight also increases the likelihood of osteoarthritis in places where weight isn’t all that significant, like your hands. A more recent explanation is that excess fat triggers chemical changes that can wreak havoc on your body (for example, inflammation that attacks the cartilage in your hands).
Source of Information : Oreilly - Your Body Missing Manual (08-2009)