For many, the word malnutrition produces an image of a person who is visibly starving. However, malnutrition is much broader than that. A person can be underweight and malnourished, but they can also be living with overweight or obesity and still be malnourished.

Malnutrition refers to an unhealthy imbalance in nutrition and does not distinguish between the consequences of too many nutrients or lack of nutrients, both of which impair overall health. There are three basic types of malnutrition including undernutrition, micronutrient deficiencies, and overnutrition such as overweight and obesity.

Another way to think about malnutrition is to separate it into two broad patterns. Undernutrition happens when the body does not get enough overall calories, protein, or nutrients to support normal growth, repair, and health. Overnutrition happens when energy intake regularly exceeds the body’s needs.

Even though it may not be as prevalent in America as in developing countries, undernutrition is not uncommon and affects many subpopulations including older adults, people living in poverty, and those with illnesses that interfere with appetite, digestion, and absorption of nutrients. Conditions such as cancer, dementia, chronic pain, AIDS, eating disorders, genetic diseases such as cystic fibrosis, autoimmune diseases such as type 1 diabetes, behavioral health disorders such as anorexia, and GI disorders can all increase the risk of malnutrition. On the other hand, overnutrition is an epidemic in the United States and is known to be a risk factor for many diseases, including type 2 diabetes, heart disease, stroke, and some cancers.

Health Risks of Being Underweight

In the U.S., underweight individuals make up a far smaller group than those with overweight or obesity, but the health risks that underweight individuals carry can be just as serious. Underweight can lead to an increase in likelihood of nutritional deficiencies, especially iron-deficiency anemia. They may also experience delayed wound healing, hormonal abnormalities, weakened immunity, lower bone density, and, in children and adolescents, stunted growth. 

In some cases, conditions such as cancer, multiple sclerosis, tuberculosis, and other wasting diseases are the cause of severe and unintentional weight loss. Nutrition support plays an important role in improving quality of life, supporting treatment, and helping the body heal. In other cases, being underweight is linked to inadequate energy intake where the body does not receive enough fuel to meet its needs. This can happen due economic reasons such as food insecurity, chronic disease, medication side effects, or intentional food restriction and disordered eating behaviors.

Eating Disorders

The National  Association of Mental Disorders defines eating disorders as “serious and sometimes fatal illnesses that cause severe disturbances to a person’s eating behaviors.”^[1] People living with eating disorders often experience a preoccupation with food choices and body weight. They may have a distorted body image, believing that self-worth is tied to body size and shape.^[2]

It is estimated that nearly 1 in 10 Americans will live with an eating disorder within their lifetime. Fewer than 6% of those with eating disorders are considered underweight by definition.^[3] Prevention and proper treatment must involve a multi-faceted approach addressing the whole person, including physical health, mental health, family and social support and nutrition. 

Anorexia Nervosa

Anorexia nervosa is characterized by an extremely low body weight, a distorted body image, and a fear of gaining weight. Anorexia nervosa results in extreme nutrient inadequacy and eventually organ malfunction. It is relatively rare—the NIMH reports that 0.9 percent of females and 0.3 percent of males will have anorexia at some point in their lifetime, but it is an extreme example of how an unbalanced diet can affect health.^[4]

Anorexia nervosa frequently manifests during adolescence, although it can emerge at any age. People with the condition may eat far too little to meet their body’s needs, exercise compulsively, or avoid entire categories of foods. Some may binge eat, followed by purging with self-induced vomiting or using laxatives or enemas. 

Signs and symptoms of anorexia nervosa

The primary signs and symptoms are:

• Fear of being overweight,
• Extreme dieting,
• An unusual perception of body image,
• Depression.

The secondary signs and symptoms are all related to the caloric and nutrient deficiencies of the unbalanced diet and include:

• Severe weight loss,
• Fatigue,
• Feeling cold all the time,
• Hair and skin changes,
• Constipation,
• Loss of menstrual periods,
• Low bone density,
• Liver, kidney, and heart failure.

Diagnosis and treatment of anorexia nervosa

No physical test can diagnose anorexia and distinguish it from other mental illnesses. Therefore, a correct diagnosis involves eliminating other mental illnesses, hormonal imbalances, and nervous system abnormalities.

Treatment includes medical monitoring, nutrition rehabilitation, psychotherapy, and family support. The goal goes far beyond simply restoring a healthy weight, but also a long-term and sustained improvement in thoughts, behaviors, and emotional health.

Bulimia Nervosa

Bulimia nervosa is another psychiatric illness that can have severe health consequences. Bulimia nervosa is characterized by recurrent episodes of eating large amounts of food, or “bingeing” followed by efforts to undo the eating, or “purging,” which is accomplished by vomiting or use of laxatives and diuretics. Unlike people with anorexia, those with bulimia nervosa are often in the normal weight or overweight range, making the disorder more difficult to detect and diagnose.^[5]

Signs and symptoms of bulimia nervosa

Physical signs and symptoms of bulimia nervosa include acid reflux, tooth enamel erosion, dehydration, electrolyte imbalances, mouth or throat irritation, and over time, esophageal injury. Repeated damage to the esophagus puts people with bulimia at an increased risk for esophageal cancer. Many people with bulimia also struggle with anxiety, depression, or obsessive thoughts about food and body weight.

Diagnosis and treatment of bulimia nervosa

Like anorexia, there are no physical tests that can be used to diagnose bulimia and distinguish it from other mental illnesses. A correct diagnosis involves eliminating other mental illnesses. 

Proper treatment includes psychotherapy, nutrition counseling, and sometimes, medications. Early treatment and involvement of family in counseling can improve outcomes.

Binge-Eating Disorder

Binge-eating disorder involves repeated episodes of eating large amounts of food while feeling unable to stop or control the eating. Unlike bulimia nervosa, there are no compensatory behaviors like purging, fasting, or excessive exercise following the binge.

People with binge-eating disorder often feel guilt, shame, or distress after a binge episode. Some have a higher BMI, as the binges can lead to weight gain over time. With the weight gain comes an increase in chronic disease associated with overweight and obesity such as type 2 diabetes, hypertension, and cardiovascular disease. It is also commonly linked with depression and anxiety.

Binge-eating disorder is more common than some other eating disorders and can seriously affect physical and mental health. Treatment includes psychotherapy, nutritional counseling, and sometimes medication to help build a steadier and less distressing relationship with food.^[6]

Other Specified Feeding or Eating Disorders (OSFED)

Not every eating disorder fits neatly into the categories above and include serious and harmful eating patterns that do not meet diagnostic criteria for a specific eating disorder. These conditions are grouped under Other Specified Feeding or Eating Disorders (OSFED).^[7] These conditions can be just as medically dangerous and emotionally distressing as the others, and include:

• Atypical anorexia nervosa (weight loss in the normal range)
• Binge eating disorder of low frequency and limited duration
• Bulimia nervosa of low frequency and limited duration
• Purging disorder (purging without binge eating)
• Night eating syndrome (excessive eating after the evening meal or waking from sleep to eat)

 Avoidant/Restrictive Food Intake Disorder

Avoidant /Restrictive Food Intake Disorder (ARFID) is characterized by individuals limiting the types and amounts of foods they will consume, but not because of fear of weight gain or body image concerns. Instead, a person with ARFID may avoid food because of low appetite, sensory sensitivity, or fear of choking or vomiting.^[8]

ARFID often begins in childhood and is different from ordinary picky eating since it can lead to weight loss, poor growth, nutrient deficiencies, and a heavy reliance on nutritional supplementation. If not treated, the condition may persist into adulthood.

Signs and symptoms may include:

• eating a very limited number of foods
• lack of interest in eating
• dramatic restriction in the amount of food eaten
• weight loss or poor growth
• nutrient deficiencies

Orthorexia

Orthorexia is a term used to describe an unhealthy obsession with healthy or “clean” eating to an extreme, leading to rigid and sometimes socially isolating behaviors. This disorder was first defined in 1997 but is not currently an official diagnosis, making it difficult to get an estimate of how many are affected. Researchers are still debating whether orthorexia is best understood as a standalone condition, or as a side effect of another disorder such as anorexia nervosa or Obsessive-Compulsive Disorder (OCD).^[9]

Signs of orthorexia include compulsively reading food labels, eliminating foods or entire food groups out of the diet, spending an unusual amount of time focusing on what foods may be available at upcoming events, experiencing a high level of distress when healthy foods are not available, spending excessive amounts of time planning meals, and difficulty eating with others in social situations. Treatment is similar to other eating disorders including psychotherapy and nutrition support.

If you think you or someone close to you might have an eating disorder and you want to learn more or find resources for help, check out these organizations and links.

• NEDA Eating Disorders Resource Center
  
• ANAD Eating Disorders Helpline

This section is an adaptation of “Undernutrition, Overnutrition, and Malnutrition” in Human Nutrition: 2020 Edition by University of Hawai‘i at Mānoa Food Science and Human Nutrition Program licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.