I am 48'and suffer eating disorder, have lost 10kms, noticing my skin is wrinkly and not so firm around the kness, would this be just from my age?

Skin elasticity: You are right in recognizing that the skin is not so elastic in your forties as it was in your teens or twenties. That and poor nutrition and weight loss will cause some sagging of the skin. Focus on healthy diet and a healthy weight for your height with your nutritionist/dietitian and physician. Best of luck.

Eating Disorder: I understand your distress, Eating disorder can be due to Depression, it can also cause depression. It can be due to stresses of relationship, marriage, separation, divorce, parenting, children leaving home, lack of support from family and friends, ongoing feelings of hurt, resentment and loneliness, work and finances. See a Psychiatrist for Therapy, Medication Do Breathing Relaxation, Yoga.