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What Are the Causes of Being Underweight?

author image August McLaughlin
August McLaughlin is a certified nutritionist and health writer with more than nine years of professional experience. Her work has been featured in various magazines such as "Healthy Aging," "CitySmart," "IAmThatGirl" and "ULM." She holds specializations in eating disorders, healthy weight management and sports nutrition. She is currently completing her second cookbook and Weight Limit—a series of body image/nutrition-related PSAs.
What Are the Causes of Being Underweight?
Negative emotions, such as sadness, can lead to reduced appetite and low body weight.

A person is considered underweight if her body weight drops below a healthy range, as designated by doctors or dietary professionals. In many cases, low body weight is associated with lethargy, trouble regulating body temperature, a weakened immune system and, in severe cases, heart complications. Although some people are genetically prone to carry lower body weight, sudden or drastic drops in a person's weight may indicate serious illness. For best results, discuss your weight-related concerns and other symptoms with your doctor.

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Poor Appetite

When a person's appetite reduces, under-eating and weight loss commonly result. According to the "New York Times," reduced appetite may occur as a symptom of an underlying disease, such as cancer, liver or kidney disease or from psychiatric disorders, such as anxiety or depression. Infections and medications can also have a numbing effect on appetite. To reduce weight loss or boost your weight to a healthier level, increased protein intake and nutritious foods that are dense in calories are recommended. Avoid skipping meals and add snacks throughout each day that include complex carbohydrates, protein and healthy fat. Examples include fruit slices topped with cheese or peanut butter, nuts, yogurt topped with granola and vitamin-fortified protein shakes.

Eating Disorders

Eating disorders, such as anorexia and bulimia, often result in dangerously low body weight. According to the American Psychological Association, people with anorexia often have a severely distorted body image and perceive themselves as "fat," even though their body weight is low. People who have bulimia, a disorder characterized by eating (often in excessive amounts, known as binges) and purging (attempting to"undo" food intake through vomiting or other means) may be underweight, normal weight or overweight. In either case, people with eating disorders are generally obsessed with weight loss and dieting. If you or a loved one has lost a significant amount of weight and struggles emotionally in regard to food and body image, seek guidance from a doctor or therapist who specializes in eating disorders for best results. Eating disorders are serious conditions that often require intensive treatment. When treatment is sought early, the chances of full, long-lasting recovery improve.

Digestive Disorders

Illnesses, such as digestive disorders, may cause unintentional weight loss. According to Johns Hopkins Medicine, digestive disorders are conditions that affect the esophagus, stomach, gallbladder, bile ducts, small intestine and large intestine (colon). Such conditions affect up to 95 million Americans, the organization reported in 2010. Digestive disorders that may result in weight loss include Celiac disease, Crohn's disease (ulcerative colitis) and irritable bowel syndrome. These disorders often cause malabsorption of nutrients, which means that the body is unable to properly process or metabolize nutrients from food. Many people experience weight loss regardless of how much they eat while suffering from these conditions. Additional symptoms of these disorders include gas, bloating, nausea, constipation and/or diarrhea. These conditions are generally treatable through dietary lifestyle changes and, in some cases, medication. If you are experiencing unintentional weight loss and suspect a digestion disorder at the root, seek proper testing and diagnosis from your doctor.

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