Missing Periods, Bone Health, and Energy Conservation: What Undernutrition Does to the Body
Author: The Narcis editorial team · updated: August 2026
🩺 Medical review: awaiting confirmation by a medical reviewer · physician who works with eating disorders
ENGLISH · Narcis editorial
What is happening underneath
When menstruation disappears during weight loss, it can be dismissed as a minor inconvenience — “At least I don’t need periods anymore.” Physiologically, however, it may signal that the body does not have enough available energy to maintain normal reproductive function.
In anorexia and chronic energy deficiency, the hypothalamic-pituitary-gonadal axis is suppressed. In women this can lead to amenorrhea; in men it can reduce testosterone and sexual function. Bone-regulating hormones also change, increasing risk of low bone density and fractures.
This is especially important in adolescence, when a large part of peak bone mass is being built. “I’ll catch up later” may not fully undo prolonged deficit during a critical developmental window.
The foundation of recovery is adequate nutrition and restoration of energy availability. Hormonal treatments may have a role in selected medical situations, but they do not substitute for nutritional rehabilitation or make an active eating disorder safe.
Psychotherapy becomes crucial at the hardest point: the very actions that protect the body — eating more, reducing compulsive exercise, restoring weight — are often what the disorder fears most. Medicine can explain the bone risk; therapy helps a person tolerate the recovery behaviors needed to reduce it.
In real life it is often less obvious
A seventeen-year-old athlete loses her period and treats it as proof of being “in shape.” At the same time, energy availability falls and bone health is affected. Psychological work matters because medically necessary recovery is experienced as a threat.
Where popular explanations oversimplify
Not every dietary change is an eating disorder, and not every eating disorder looks dramatic. The central question is whether food, weight, or compensatory behavior has begun to control life disproportionately and whether health risks are emerging.
Where psychotherapy is genuinely useful
For some clients, CBT-ED or another specialized eating-disorder therapy is central; for adolescents, family involvement can be crucial. Treatment is chosen by age, diagnosis, risk, and maintaining mechanisms—not by therapeutic fashion.
How to test the hypothesis against reality
With eating disorders, weight and diagnostic label are not enough. For “this topic,” track specific behavior — restriction, binge episodes, purging, compulsive exercise, food fear — its frequency and trajectory, physical symptoms such as fainting, weakness, palpitations, vomiting or menstrual changes, and how much of life is occupied by food and body concerns. Medical risk can be serious at any body size. Psychotherapy addresses mechanisms that maintain symptoms, but it does not replace medical assessment, physical/laboratory monitoring, or nutritional rehabilitation. Rapid deterioration or physical instability requires urgent care.
Medical note. Appearance does not show eating-disorder severity. If behaviors escalate quickly or physical symptoms appear, do not wait for weight to become “low enough” or for the illness to match a stereotype.
Books and sources
• Schorr & Miller. Endocrine complications of anorexia nervosa. 2023.
• Misra & Klibanski. The endocrine manifestations of anorexia nervosa: mechanisms and management.
If this topic resonated — you do not have to sit with it alone.
Find a therapist for this topic →If there is an immediate threat to your life, thoughts of self-harm, or a sharp worsening of your state, do not wait for a scheduled session — seek emergency help. Where to turn →
This article is for information only and is not a substitute for an individual consultation with a specialist.