Just as a house rests on a foundation, the skin rests on the hypodermis, the layer of connective tissue in fat cells beneath the dermis that attaches it to the underlying bone and muscle. The hypodermis is the layer of skin that can be used to estimate total body fat. The skin and hypodermis are pinched at selected locations, and the thickness of the fold of skin and underlying hypodermis is recorded. The thicker the fold, the greater the amount of total body fat.