Under the top layer of your skin are a capillary bed of cells called the dermis. Small blood vessicles take oxygenated blood to this area and thus your skin should be "pink" and healthy. In larger individuals, it's easy to get rashes, skin openings as the adipose tissue is choking some of the blood supply. So in heavily obese patients, especially with type 2 diabetes will be at greater risk of tissue damage and nerve damage as less oxygenated blood can get to those areas. People that exercise or get enough incidental exercise can for example blush or get red in the face if exercising, as the blood is being circulated around the skin. In morbidly obese patients it is common for them not to get cold, or to have pressure sores and skin splits because they can't feel it as such.