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How Calorie-Restrictive Eating Disorders Can Lead to an Underactive Thyroid

How Calorie-Restrictive Eating Disorders Can Lead to an Underactive Thyroid


By Thrive Reno’s Director of Primary Care Services Becky Barnett, PA-C


The butterfly-shaped thyroid gland resides at the base of the throat and is part of the human body’s endocrine system, which produces hormones that impact almost every cell, organ, and function within the body. While tiny, the thyroid gland has big responsibilities. Its role is to regulate vital body functions by releasing hormones into the bloodstream. Thyroid hormones affect the entire body, most notably having a major influence on metabolism, growth, and development. 


When an individual is experiencing a calorie-restrictive eating disorder such as anorexia nervosa, the thyroid may slow its production and secretion of hormones as a response to lack of nourishment. The decrease in hormones slows the metabolism down in an effort to preserve the body’s energy. When severe starvation occurs, the thyroid gland can atrophy or shrink in size and weaken.


Low levels of thyroid hormones (hypothyroidism) can have far-reaching consequences for many of the body’s metabolic-associated processes, including:

  • Slowed heart rate: A lack of thyroid hormones can hinder the strength and speed of one’s heartbeat.
  • High cholesterol: An underactive thyroid can cause the liver to process blood slower, which can result in a build-up of cholesterol in the arteries.
  • Reduced metabolic functioning: Insufficient levels of thyroid hormones can lessen the rate at which food and drink are used as energy. 
  • Decreased body temperature: A slowed metabolism can lead to a drop in core body temperature, causing a person to feel persistently cold.
  • Digestive function: A slowed metabolism can cause constipation to occur.
  • Muscle pain and discomfort: Low levels of thyroid hormones can cause muscle weakness, aches, and cramping.
  • Decreased cognitive functioning: A slowed metabolism may cause symptoms of “brain fog,” including forgetfulness, tiredness, confusion, delayed reaction times, and difficulty concentrating.
  • Symptoms of depression: An underactive thyroid can cause similar symptoms to depression such as fatigue, social withdrawal, apathy, anxiousness, and irritability.

Because many of the symptoms of an underactive thyroid overlap with the symptoms of eating disorders, blood testing is typically necessary to diagnose low levels of thyroid hormones.


Individuals in eating disorder recovery can re-establish and maintain the health of their thyroid by increasing their caloric intake and restoring their body weight. In other words, once a person begins their recovery journey, their thyroid function tends to normalize, as with most processes in the body.


Thrive offers expert-led eating disorder treatment that focuses on healing clients’ physical, mental, and emotional well-being. Reach out to us to learn more.

About the Author

Becky Barnett, PA-C — Thrive Reno Director of Primary Care Services

Becky Barnett, PA-C, has worked as a Physician Assistant for over 25 years with a primary focus on women’s health. She earned a bachelor’s degree from U.C. Riverside in 1991, and graduated from the College of Osteopathic Medicine of the Pacific (now Western University of Health Sciences) as a Physician Assistant in 1995. She has worked in various venues including community health centers, residential mental health facilities, large HMO settings and private practices as she moved throughout California and then into Nevada in 2001. She is proud to represent the medical team of Thrive Wellness of Reno, and is thrilled to be a part of such an authentic and passionate group.

Becky has two sons who attend schools in the Washoe County School District. She enjoys taking weekend excursions into the various wonders Northern Nevada has to offer, going on cruises, and spending time with her friends and family.