The Impact of Food Restriction on the Body
Food Restriction & Malnutrition and Eating Disorders
Restriction in some form is an essential criterion present in several eating disorder classifications.1 Restriction can take the form of no food intake, eating minimal amounts of food, only eating specific foods in specific amounts, or fasting for large portions of the day. Prolonged food restriction often leads to malnutrition, which impacts every organ system and can cause various medical complications.
Restriction in Diagnostic Criteria
Several eating disorders feature restriction within the diagnostic criterion, including the restrictive subtype of anorexia nervosa and other specified feeding or eating disorder.
Anorexia Nervosa Restrictive Subtype
- Food restriction is most often associated with anorexia nervosa. Anorexia nervosa (AN) is an eating disorder categorized by:
- Restriction of energy intake relative to requirements, leading to significantly low body weight in the context of age, sex, developmental trajectory, and physical health
- Intense fear of gaining weight or becoming fat or persistent behavior that interferes with weight gain
- Disturbed by one's body weight or shape, self-worth influenced by body weight or shape, or persistent lack of recognition of the seriousness of low body weight
Anorexia nervosa is further divided into two subtypes: restricting type (AN-R) and binge-eating/purging type (AN-BP). AN-R is categorized by the above criteria, combined with not engaging in binge eating or purging within the last three months.1
Bulimia nervosa (BN) is an eating disorder characterized by cyclical episodes of binge eating and compensatory behavior. A binge eating episode is eating an amount of food in a discreet amount of time that is definitively larger than what most individuals would eat in a similar period under similar circumstances while also feeling that one cannot stop eating or control what or how much they are eating. Individuals with BN will engage in recurrent inappropriate compensatory behaviors to prevent weight gain, including restriction or fasting. On average, binge eating and compensatory behaviors occur at least once a week for three months.1
Avoidant Restrictive Food Intake Disorder (ARFID)
Avoidant Restrictive Food Intake Disorder (ARFID) is categorized by:
- Significant weight loss (or failure to achieve expected weight gain or faltering growth in children)
- Significant nutritional deficiency
- Dependence on enteral feeding or oral nutritional supplements
- Marked interference with psychosocial functioning1
Unlike other eating disorders, ARFID features no image disturbance, fear of gaining weight, or desire for thinness. Three subtypes of ARFID have been suggested and validated in medical literature, including:
- Sensory: when individuals avoid certain types of food due to sensory features (smells, textures, appearance, or color)
- Lack of interest: when individuals show little-to-no interest in food (forgetting to eat, low appetite, or pickiness)
- Fear of adverse consequences: when individuals experience food-based reactions to food (fear of choking, nausea, vomiting or pain)
While individuals with ARFID do not purposefully restrict their food intake with the intent to limit their energy intake or initiate weight loss like anorexia nervosa or bulimia nervosa, their eating disturbance can still cause malnutrition.
Other Specified Feeding or Eating Disorder (OSFED)
According to the DSM-5, the category of other specified feeding or eating disorder (OSFED) applies to individuals experiencing significant distress due to symptoms similar to eating disorders but who do not meet the full criteria for diagnosing one of these disorders. One experience that may display in OSFED is atypical anorexia.1
Atypical Anorexia Nervosa
Atypical anorexia nervosa (A-AN) is characterized by an individual either meeting all the criteria for anorexia nervosa except their final weight is at or above their ideal body weight (IBW) or when some but not all the criteria for anorexia nervosa are met (for example, occurring for less than three months).1,2
Complications from Restriction & Malnutrition: Head to Toe
The medical complications of eating disorders affect the entire body, head to toe. Food restriction patients are often malnourished, leading to neurological, musculoskeletal, gastrointestinal, cardiovascular, pulmonary, hepatic, endocrine, and dermatological problems.
Prolonged starvation affects the entire body, including the brain. Patients typically report "brain fog," a catchall term that refers to a decline in concentration, memory, and cognitive flexibility and function.
Brain atrophy, or a "starved brain," is a loss of brain mass due to severe malnutrition. Brain atrophy can be significant in patients with eating disorders, particularly those with anorexia nervosa. The most severe cases can appear on magnetic resonance imaging (MRI) and are often indistinguishable from the brain of those with Alzheimer's disease. Brain atrophy impacts both white and grey matter in the brain.3 While it has not been explicitly studied in patients with eating disorders, shrinkage of the brain has been associated with problems with speech and language, memory, organizing and planning, abstract thinking, and learning, which can explain deficits experienced by some patients.3
Eating disorders increase the risk of bone health issues, including osteopenia, osteoporosis, and fractures. The severity of musculoskeletal complications is directly related to the age of onset and length of the disease.
Decreased Bone Mineral Density
As individuals with an eating disorder lose weight, their body composition changes. They begin losing lean muscle mass, which is essential to bone growth. Bone mineral density increases due to muscle exerting force onto the bone during activity. A lower weight, combined with diminished activity and decreased skeletal muscle mass due to malnutrition, decreases bone mineral density over time, putting patients at risk for developing osteopenia and osteoporosis, and fractures.
Decreased bone mineral density is more common in individuals with a lower age of onset, as bone accrual peaks during adolescence.
Osteopenia & Osteoporosis
Osteopenia (mild loss of bone mineral density) and osteoporosis (severe loss of bone mineral density) are some of the most common medical complications of eating disorders, with about 85% of women with anorexia nervosa having either. For men, the rates for osteopenia and osteoporosis are 26% and 36%, respectively.
Decreased bone mineral density and worsened bone health increase an individual's risk for lifetime fractures. Anorexia nervosa is associated with a three-fold increase in lifetime risk of fracture, and 57% of women with anorexia nervosa sustain at least one fracture in their lifetime.4
Those with a younger age of onset may never reach peak bone mass, which puts them at risk for other problems with their bones and joints, including:
- Chronic pain from bone fractures
- Reduced strength and mobility
- Shorter stature
Gastrointestinal complications are one of the biggest complaints of eating disorder patients. Food restriction and malnutrition can cause an underuse of the gastrointestinal tract, leading to numerous complications.
Food restriction, accompanied by a weight loss of 15-20% under the ideal body weight, is almost universally followed by gastroparesis or delayed gastric emptying. Shorts bouts of anorexia nervosa are seemingly less likely to cause gastroparesis than chronic or more enduring cases. Gastroparesis can worsen as patients eat fiber-rich foods to promote gastrointestinal transit.2,5
Constipation & Bloating
Gastroparesis, constipation, and bloating frequently accompany weight loss and malnutrition, with many patients reporting infrequent or small stool. Patients may begin increasing their fiber intake or use bulking laxatives in an attempt to produce a bowel movement, but instead, worsen constipation and cause bloating or distention.2,5
Superior Mesenteric Artery Syndrome (SMA)
Significant weight loss causes thinning of the mesenteric fat pad surrounding the superior mesenteric artery (SMA), causing the duodenum to become compressed between the aorta, spine, and SMA, narrowing the angle between the two blood vessels and entrapping the duodenum, causing abdominal pain after eating, early satiety, nausea, and vomiting.5,6
Dysphagia (difficulty swallowing)
Patients can experience functional or oropharyngeal dysphagia. The muscle loss and weakness associated with severe food restriction and excessive weight loss can impact the throat muscles responsible for swallowing, leading to oropharyngeal dysphagia, where it is difficult to move food, liquid, or saliva from the mouth to the throat. A small study suggests that oropharyngeal dysphagia occurs most often in the most critically ill anorexia nervosa patients.7
While those with an eating disorder can also experience functional dysphagia, where the individual has difficulty swallowing, no anatomical abnormality or injury, and may affect up to 6% of those with eating disorders.8
Acute Pancreatitis is a rare complication but can occur during the refeeding process. It typically presents with nausea, vomiting, and epigastric pain. It is assumed that malnutrition activates trypsin, a digestive protein, and injures pancreatic cells, causing pancreatitis.2,5,6
Cardiovascular complications are some of the most common and serious complications of eating disorders and severe malnutrition. While suicide represents nearly half of the mortality of patients, many of the remaining causes of death are cardiac.16
Bradycardia (low heart rate)
Bradycardia, an abnormally low heart rate under 60 beats per minute (bpm), is the most common medical complication in eating disorder patients, occurring in 95% of patients with anorexia nervosa. It may be the first medical implication of an eating disorder.5,9
It is suggested that heightened vagal tone is the cause of bradycardia, as the body attempts to conserve energy. However, findings to support this have been inconsistent. Bradycardia can also cause:
- Syncope (fainting)
- Chest pain
- Heart failure
Hypotension (low blood pressure)
Chronic malnutrition causes the body to break down tissue for fuel, including muscle tissue; it is indiscriminate and includes the heart, decreasing heart muscle mass and weakening the heart over time. It can cause the heart to struggle to pump blood throughout the body, resulting in the following:
- Blurred vision
- Cold, clammy skin
- Shallow breathing
The rapid weight loss, low BMI, low T3 levels, and low IGF-1 levels seen in patients with anorexia nervosa1 can cause pericardial effusion (buildup of too much fluid in the pericardium), which presents in anywhere between 22% and 71% of patients.5
Decreased Left Ventricular Size
Patients with anorexia nervosa may also have decreased left ventricular mass, left ventricular index, cardiac output, and left ventricular diastolic and systolic dimensions. Chronic hypovolemia (a condition in which plasma is too low) has been theorized as the cause.5
For a long time, it was believed that the lungs were immune to the effects of severe malnutrition. Still, several findings show patients with eating disorders can suffer from pulmonary complications like pneumonia and emphysema.
Dysphagia can cause lead to aspiration pneumonia when food or liquid is breathed into the airways or lungs instead of being swallowed and cause infection of the lung tissue.2,5
Multiple reports show emphysema in patients with eating disorders, regardless of smoking history. In emphysema, the lungs' alveoli (air sacs) are damaged, causing them to rupture and create a larger space instead of the typical, smaller spaces. This reduces the surface area available for gas exchange, causing shortness of breath, coughing, and fatigue.5,13,15
Being malnourished increases the risk for collapse of the lung with surrounding air, or pneumothorax. Both those who restrictor and purge seem to be at risk for this condition. Pneumothorax presents with shortness of breath and chest pain.
Abnormal liver transaminases (AST & ALT)
Liver transaminases (AST & ALT) are often abnormal in anorexia nervosa, occurring in almost half of all anorexia nervosa patients. Weight loss and fasting can produce mild elevation (2-3x normal) of AST/ALT during early refeeding, while severe elevation (4-30x normal) can occur with severe malnutrition, even before refeeding. It is more likely to occur in patients with a body mass index (BMI) less than 12/kg/m2 and may be a sign of multi-organ failure.5
While the cause is unknown, it is suggested to be due to autophagy or organ hypoperfusion due to myocardial dysfunction.5
Prolonged starvation significantly impacts the pituitary gland, thyroid gland, adrenal glands, gonads, and bones. Many of these hormonal changes are appropriate physiologic adaptations to help conserve energy but come to the detriment of bone health and other physiologic abnormalities.
Euthyroid Sick Syndrome
The malnutrition associated with food restriction can cause the hypothalamic-pituitary-thyroid axis to become dysregulated. Euthyroid sick syndrome, or nonthyroidal illness syndrome, is characterized by low triiodothyronine (T3) levels and low-to-normal thyroxine (T4) and thyroid stimulating hormone (TSH).4 To conserve energy, the malnourished body converts T4 to the inactive reverse T3 in the periphery instead of the active T3 hormone.5
Abnormal Glucose Metabolism & Hypoglycemia
Prolonged starvation can cause low levels of blood glucose. Coupled with a low BMI, insulin levels are also low. Insulin helps the body utilize blood sugars for metabolism, and reduced insulin levels cause other metabolic pathways to help increase blood glucose levels through the breakdown of fatty acids to allow increased production of glucose and the breakdown of glycogen (stored polymers of glucose). The body remains at high risk for hypoglycemia, which can result in coma and death due to hepatic glycogen stores and reduced adipose (fat) tissue depletion.
Cortisol, the body's primary stress hormone, is up-regulated in starvation. There also appears to be increased levels of corticotropin-releasing hormone (CRH), a hormone secreted from the hypothalamus that increases the production of cortisol. Cortisol plays a vital role in regulating metabolism, but it can also impact the immune response, increase the bone breakdown and contribute to the development of gastritis.12
Low Sex Hormones
Malnutrition can cause a disruption of the hypothalamic-pituitary-gonadal axis in both males and females. This hormonal disruption causes hypothalamic hypogonadism, which can cause decreased estrogen, amenorrhea, infertility in women, low testosterone levels, lowered sex drive, and reduced sexual function in men.
Typically, the hypothalamus secretes gonadotropin-releasing hormone (GnRH) in a pulsatile manner, causing increased secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland, causing the production of various hormones from the ovaries or testes that ultimately result in increased levels of progesterone and estradiol in females and testosterone in males.2,5,10,11
Many dermatological signs of eating disorders are caused by severe malnutrition, affecting all areas of the body.14
Xerosis (dry skin) & Pruritis (itchy skin)
Xerosis, or dry skin, is seen in almost all patients with severe malnutrition. Dry skin can range from mild dryness to scalier skin. Prolonged starvation reduces the activity of the sebaceous glands, which produce sebum (lubricating oil) for the skin and hair, causing dry skin. Xerosis can also cause nail fragility and lipid depletion of the nail. Patients with eating disorders frequently have itchy skin, but their dry skin typically causes this.14
Lanugo-Like Body Hair
Lanugo-like body hair is fine, downy, and pigmented hair on the back, abdomen, and forearms. Lanugo-like body hair is frequently seen in eating disorder patients, particularly younger patients, and typically doesn't appear in other forms of chronic malnutrition. Lanugo hair is associated with decreased activity of the 5-α-reductase enzyme system (enzymes involved in steroid metabolism) and probably occurs due to hypothyroidism.L It may also be an attempt of the body to conserve heat.5,14
Telogen Effluvium (hair loss)
Hair loss is another common feature of eating disorders. The hair loss typically follows a diffuse pattern, occasionally with frontal prominence. There is usually an increased number of telogen hairs and opaque hairs.14
Individuals with an eating disorder will opt to eat carotenoid-rich vegetables because they are low in calories. Carotenoids are classes of yellow, orange, and red fat-soluble pigments. They give plants their color, including foods like tomatoes, pumpkins, and carrots. When excessively consumed, they deposit orange or yellow pigment into the skin, causing orange-yellow discoloration, called carotenoderma. It can also affect the nails.14
Acrocyanosis (unnatural pale appearance)
Acrocyanosis is when the extremities and face are blueish or pale in appearance due to decreased oxygen delivery. Acrocyanosis often occurs alongside bradycardia and high plasma glucose levels. It is also seen more commonly in the most critically ill patients. It is suggested that acrocyanosis is an extreme form of heat conservation.14
Acrocyanosis occurs during Raynaud's phenomenon, which can also be characteristic of malnutrition. Acrocyanosis means bluish discoloration of the extremities due to decreased oxygen delivered to the peripheral part. It is a persistent disorder without episodic triphasic color response. Acrocyanosis is usually painless and is often triggered by heat, cold, or stress.14,15
Cheilitis & Angular Stomatitis
Riboflavin and vitamin deficiencies in eating disorder patients may cause angular stomatitis, an inflammatory skin condition of the corners of the mouth that causes painful, cracked sores. Patients can also experience cheilitis (inflammation of the lips).14
Other than yellowing nails caused by carotenoderma and fragile nails due to xerosis, prolonged starvation can cause other problems with the pins. Iron deficiency can cause koilonychia, spoon nails, and nails with significant dips. Patients with eating disorders also report periungual edema (swelling around the nail), which may cause onychocryptosis (ingrown toenails).14
Slow Wound Healing
Patients with eating disorders may experience lower wound healing due to compensatory hypothyroidism and zinc deficiency.14
Vitamin and Mineral Deficient Diseases
Malnutrition can cause vitamin and mineral deficiencies that cause several diseases:
- Pellagra (vitamin B3 deficiency)
- Scurvy (vitamin C deficiency)
- Acrodermatitis enteropathica (zinc deficiency)14
Other Dermatological Complications
Many other dermatological complications occur as a result of prolonged starvation:
- Livedo reticularis (muddled net pattern on the skin)
- Prurigo pigmentosa (recurrent itchy rash with hyperpigmentation)
- Pompholyx (dyshidrotic eczema; eczema in the form of blisters across the hands and feet)
- Eruptive neurofibromatosis (eruption of papules across the torso and trunk)
- Pili torti (fragile hair)
- Folliculitis (bacterial infection of the hair follicle)
- Decubitus ulcers (bedsores)
- Stritae distensae (stretch marks)14
- American Psychiatric Association. (2013). Feeding and Eating Disorders. In Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596.
- Mehler, P. S., & Andersen, A. E. (2017). Eating Disorders: A Guide to Medical Care and Complications (third edition). Johns Hopkins University Press.
- National Institute of Neurological Disorders and Stroke. (n.d.). Cerebral Atrophy. Retrieved March 5, 2023, from https://www.ninds.nih.gov/health-information/disorders/cerebral-atrophy
- Steinman, J., & Shibli-Rahhal, A. (2019). Anorexia Nervosa and Osteoporosis: Pathophysiology and Treatment. Journal of Bone Metabolism, 26(3), 133. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746661/
- Mehler, P. S., & Brown, C. (2015). Anorexia nervosa – medical complications. Journal of Eating Disorders, 3(1). https://doi.org/10.1186/s40337-015-0040-8
- Mehler, P. S., Krantz, M. J., & Sachs, K. (2015). Treatments of medical complications of anorexia nervosa and bulimia nervosa. Journal of Eating Disorders, 3(1). https://doi.org/10.1186/s40337-015-0041-7
- Holmes, S. C., Sabel, A. L., Gaudiani, J. L., Gudridge, T. A., Brinton, J. T., & Mehler, P. S. (2016). Prevalence and management of oropharyngeal dysphagia in patients with severe anorexia nervosa: A large retrospective review. International Journal of Eating Disorders, 49(2), 159–166. https://pubmed.ncbi.nlm.nih.gov/26316316/
- Wang, X., Luscombe, G., Boyd, C., Kellow, J., & Abraham, S. (2014). Functional gastrointestinal disorders in eating disorder patients: Altered distribution and predictors using ROME III compared to ROME II criteria. World Journal of Gastroenterology, 20(43), 16293. https://doi.org/10.3748/wjg.v20.i43.16293
- Yahalom, M., Spitz, M., Sandler, L., Heno, N., Roguin, N., & Turgeman, Y. (2013). The Significance of Bradycardia in Anorexia Nervosa. International Journal of Angiology, 22(02), 083–094. https://doi.org/10.1055/s-0033-1334138
- Usdan, L. S., Khaodhiar, L., & Apovian, C. M. (2008). The Endocrinopathies of Anorexia Nervosa. Endocrine Practice, 14(8), 1055–1063. https://doi.org/10.4158/ep.14.8.1055
- Wong, H. K., Hoermann, R., & Grossmann, M. (2019). Reversible male hypogonadotropic hypogonadism due to energy deficit. Clinical Endocrinology. https://doi.org/10.1111/cen.13973
- Kano, M., Muratsubaki, T., Von Oudenhove, L., et al. (2017). Altered brain and gut responses to corticotropoin-releasing hormone (CRH) in patients with irritable bowel syndrome. Scientific Reports, 7, 12425. https://www.nature.com/articles/s41598-017-09635-x
- Cleveland Clinic. (2022, November 29). Emphysema: Causes, Symptoms, Diagnosis & Treatment. Clevelandclinic.org. Retrieved March 6, 2023, from https://my.clevelandclinic.org/health/diseases/9370-emphysema
- Strumia, R. (2005). Dermatologic Signs in Patients with Eating Disorders. American Journal of Clinical Dermatology, 6(3), 165–173. https://doi.org/10.2165/00128071-200506030-00003
- American College of Rheumatology. (2021, December). Raynaud’s Phenomenon. rheumatology.org. Retrieved March 5, 2023, from https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Raynauds-Phenomenon
- Isner, J. M., Roberts, W. C., Heymsfield, S. B., & Yager, J. (1985). Anorexia Nervosa and Sudden Death. Annals of Internal Medicine, 102(1), 49. https://pubmed.ncbi.nlm.nih.gov/3966745/