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. Restriction can take the form of no food intake, eating minimal amounts of food, only eating specific foods, eating 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 a variety of medical complications.

Restriction in Diagnostic Criteria

Several eating disorders feature restriction within the diagnostic criteria, 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).

Bulimia Nervosa

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.

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 functioning

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, such as atypical anorexia nervosa.

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).

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. 

Neurological Complications

Prolonged starvation affects the entire body, including the brain. Patients typically report "brain fog," a catch all term that refers to a decline in concentration, memory and cognitive flexibility and function.

Brain Atrophy

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. Magnetic resonance imaging (MRI) will often show significant loss of mass. Brain atrophy impacts both white and grey matter in the brain, which may contribute to various cognitive, emotional, and motivational processing deficits.

Musculoskeletal Complications

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. Sarcopenia, or reduced muscle mass, is also associated with malnutrition.

Decreased Bone Mineral Density

As individuals with an eating disorder lose weight, their body composition changes. They begin losing lean muscle mass, and in turn may lose essential bone growth since the forces exerted on bones via muscle contraction are what cause increased bone growth.

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, osteoporosis and fractures. Hormonal changes also contribute to reduced bone mineral density. 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 40% of women with anorexia nervosa having osteoporosis and about 92% of individuals having osteopenia.  

Brittle Bones

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.

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 

Gastrointestinal complications are one of the biggest complaints of eating disorder patients.

Gastroparesis

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. Gastroparesis symptoms of bloating, fullness, and nausea can worsen as patients eat fiber-rich foods to promote gastrointestinal transit, due to the longer digestion times.

Slow Transit Constipation

Gastroparesis, constipation, and bloating frequently accompany weight loss and malnutrition, with many patients reporting infrequent or small stool. Similar to the slowed emptying of the stomach, intestinal transit time is also prolonged, likely as a compensatory mechanism to increase nutrient uptake. Patients may begin increasing their fiber intake or using bulking laxatives in an attempt to produce a bowel movement but this will often lead to worsening symptoms due to the effects on gastroparesis.  

Superior Mesenteric Artery (SMA) Syndrome

Significant weight loss causes atrophy of the mesenteric fat pad surrounding the SMA, causing the angle between the SMA and the aorta to narrow, thereby compressing the duodenum. This is associated with abdominal pain after eating, early satiety, nausea, and vomiting.Treatment consists of weight restoration.

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.

Cardiovascular Complications

Cardiovascular complications are some of the most common presentations in individuals with eating disorders and severe malnutrition.

Bradycardia

Bradycardia, an abnormally low heart rate under 60 beats per minute (bpm), is the most common medical complication in eating disorder patients, occurring in up to 95% of patients with anorexia nervosa. It may be the first medical implication of an eating disorder.

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 contribute to syncope (fainting) and cardiac pauses, with the latter potentially leading to more catastrophic arrhythmias.

Hypotension

Chronic malnutrition causes the body to break down tissue for fuel, including muscle tissue; it is indiscriminate in the tissues it affects and includes the heart, causing decreased cardiac muscle as well. This can be associated with:

• Dizziness
• Nausea
• Fatigue
• Blurred vision
• Cold, clammy skin
• Confusion
• Tachycardia (fast heart rate)

Pericardial Effusion

Fluid around the heart (pericardial effusion) is presumed to develop in about 25% of those with anorexia nervosa. It may be related to fat and cardiac atrophy or potentially abnormal thyroid hormone but is only rarely a cause of concern. In rare instances when excess fluid builds up surrounding the heart, a condition called cardiac tamponade can develop, leading to reduced cardiac output.

Pulmonary Complications

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. However, the lungs seem to be just as impacted as the other organs.

Aspiration Pneumonia

Dysphagia can cause lead to aspiration pneumonia when food or liquid is breathed into the airways or lungs instead of being swallowed into the esophagus, contributing to inflammation and/or infection.

Emphysema

Some studies suggest emphysema can develop 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.

Pneumothorax

Being malnourished increases the risk for collapse of the lung, or pneumothorax. Both those who restrict and purge seem to be at risk for this condition. Pneumothorax typically presents with shortness of breath and chest pain.

Hepatic Complications

Abnormal Liver Transaminases (AST & ALT)

Liver transaminases (AST & ALT) are often abnormal in anorexia nervosa. Greater severity of weight loss contributes to increased elevation in the AST and ALT, and it is more likely to occur in patients with a body mass index (BMI) less than 12/kg/m². It is seemingly caused by autophagy, or programmed cell death. Refeeding can be another cause of increased AST and ALT, known as refeeding hepatitis.

Endocrine Dysfunction

Prolonged starvation significantly impacts hormones from the pituitary gland, thyroid gland, adrenal glands, and gonads. 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/non-thyroidal illness 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 most commonly characterized by low triiodothyronine (T3) and thyroxine (T4) levels with low to normal thyroid stimulating hormone (TSH). To conserve energy, the malnourished body converts T4 to the inactive reverse T3 in the periphery instead of the active T3 hormone.

Abnormal Glucose Metabolism & Hypoglycemia

Prolonged starvation can cause low levels of blood glucose (hypoglycemia). Coupled with a low BMI, insulin levels are also low. Insulin helps the body utilize blood sugars for metabolism, and reduced insulin levels contribute to the body using fats/proteins as an energy substrate, creating a state of catabolism. The body remains at high risk for hypoglycemia, which can result in coma and death due to depleted glycogen stores.

Cortisol Dysregulation

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 bone breakdown and contribute to the development of gastritis.

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.

Dermatological Signs

Many dermatological signs of eating disorders are caused by severe malnutrition, affecting all areas of the body.

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. Patients with eating disorders frequently have itchy skin, with xerosis contributing to this. 

Lanugo-Like Body Hair

Lanugo-like body hair is fine, downy, and pigmented hair on various body parts. 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. It may also be an attempt of the body to conserve heat.

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.

Carotenoderma

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.

Acrocyanosis

Acrocyanosis is when the extremities develop a bluish appearance. It is suggested that acrocyanosis is an extreme form of heat conservation.

Raynaud's Phenomenon

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.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).

Nail Dystrophy

Other than yellowing nails caused by carotenoderma and fragile nails due to xerosis, prolonged starvation can cause other problems with the nails. 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 contribute to onychocryptosis (ingrown toenails).

Slow Wound Healing

Patients with eating disorders may experience lower wound healing. Zinc deficiency may further contribute to poor wound healing.

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)

Resources

• 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.
• Grinspoon, S., Thomas, E.R., Pitts, S., et al. (2000). Prevalence and predictive factors for regional osteopenia in women with anorexia nervosa. Annals of Internal Medicine
• 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/
• 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
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• Nitsch, A., Kearns, M., Mehler, P. (2023). Pulmonary complications of eating disorders: A literature review. Journal of Eating Disorders, 11(1), 12.
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• 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/
• 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
• 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
• 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
• 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
• 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

Last Reviewed: December 2023 by Dennis Gibson, MD, FACP, CEDS