Bone and skin are connective tissues, and in both the major organic constitute is type I ­collagen. The relationship between skin and bone has been investigated in many articles. Savas et al. [1] reported a simultaneous decrease in skin collagen content, skin thickness and bone mineral density in women with a 4-year period of amenorrhoea due to anorexia nervosa (AN). This association supports the hypothesis that a generalized loss of collagen is a major factor in the causation of osteoporosis following oestrogen deficiency.

Moreover, in AN there is often a vegetarian lifestyle that has an impact on fat metabolism causing a remarkable stimulation of carnitine uptake and a reduction in collagen synthesis-associated genes [2]. In addition, an increased risk of osteoporosis, which is also known to be associated with a lowered collagen synthesis, has been associated in vegetarians with a low cobalamin (vitamin B12) status.