There is an interesting trend that links obesity to higher risk of inflammation. In fact, some define obesity as chronic inflammatory disease.
For instance, at the physical level, heavier weight can exert greater pressure and stress on knee joint, accelerating the onset of Osteoarthritis.
For another example, obesity significantly increases the risk of fatty liver, which in turn increases the risk of hepatitis, inflammation of liver.
At a physiological level, some research findings suggest that obese people tend to have higher level of inflammatory markers. In one finding, unfit men or those with high BMI had higher level of white blood cells- an inflammatory marker. Another study showed that obese patients tended to have higher level of fibrin, another marker of inflammatory reactions.