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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Man to Man Man to Man

Dealing with Unintentional Weight Loss

April 16, 2013

By Harvey B. Simon M.D.

Harvard Medical School


Some guys have all the luck — or so it seems.

Many men struggle to lose weight. Then there are the guys who shed pounds without even trying. But before you turn green with jealousy, ask if they are really the lucky ones. Unintended weight loss may be easy but can have some serious consequences.

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Age-Related Weight Loss

A typical adult starts putting on pounds in his 20s and 30s, mostly in the form of body fat. Slow, steady weight gain continues until the 40s and 50s, when body weight stabilizes. But in the 60s and beyond, the opposite happens: An adult often loses weight.

In healthy people, age-related weight loss is normal and gradual — perhaps two to five pounds a decade. It's usually the result of a decrease in appetite and food intake, especially in men. But although mild age-related weight loss is normal, it may have negative effects.

People usually lose muscle, not fat. In fact, the average 30 year-old can expect to lose about 25% of his muscle mass and strength by age 70 and another 25% by age 70. Doctors call this loss of muscle sarcopenia. Although some men take testosterone to address the problem, strength training exercises and a balanced diet that provides enough protein is a much better remedy.

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Causes of Unintentional Weight Loss

Most doctors see the loss of 10 pounds or 5% of body weight over a 6- to 12-month period as abnormal. And a 10% weight loss indicates protein-energy malnutrition, which is much more worrisome.

Various studies report a 9% to 38% death rate within 1 to 2.5 years of substantial unintentional weight loss. That's why it gets the attention of doctors and patients alike.

Unintentional weight loss in adults is usually caused by medical illnesses, psychosocial problems or unknown factors.

Medical Problems

  • Cancer. Cancers account for about one-quarter to one-third of all cases of unintentional weight loss. Although virtually any cancer can cause weight loss, gastrointestinal (GI) tumors are the leading culprits. In many cases, a diagnosis of cancer is established before significant weight loss occurs, but in some people, weight loss is the first sign of trouble.
  • Gastrointestinal disorders. GI disorders rank second among the medical cause of weight loss. Poor teeth, dry mouth and loss of taste (and smell) are often responsible for a person eating less and losing weight. Diseases that produce abnormal intestinal contractions, nausea, impaired absorption of nutrients or abdominal pain can also lead to substantial weight loss.
  • Endocrine disorders. Diabetes and thyroid disorders head the list, but in rare cases, abnormalities of the adrenal or parathyroid glands can trigger weight loss.
  • Neurologic diseases. Patients with dementia or milder forms of cognitive impairment often lose interest in food. Stroke, Parkinson's disease and multiple sclerosis can also cause involuntary weight loss.
  • Other chronic diseases. It's a long list that includes chronic lung disease, heart failure, advanced kidney or liver disease and infections ranging from tuberculosis to AIDS.
  • Medications. It's often the last thing people think about, but it should be one of the first things doctors ask about. Many, many drugs can contribute to weight loss by decreasing appetite, blunting taste and smell, producing dry mouth, causing GI pain, or triggering nausea, vomiting, or diarrhea. Drug side effects are particularly difficult to sort out in people who take multiple medications.

Psychosocial Problems

Loss of appetite is a key symptom of depression. Over time, it can lead to substantial weight loss.

Social and economic problems are distressingly common, particularly in the elderly. Illness and frailty can limit people's ability to shop, cook and even feed themselves. Social isolation may put helping hands out of reach. And poverty can make it hard for people to afford enough food to maintain their weight.

Unknown Causes

Doctors can't find the cause for unintended weight loss in 16 to 28% of patients. In any case, people who lose weight without an apparent cause tend to fare better than those who lose it because of a major medical or psychosocial problem.

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Medical Detective Work

Doctors start by taking a careful medical history. This should always include a review of medications and supplements as well as an evaluation of the patient's psychological state and social circumstances. The doctor will also want to see a record of the weight loss over time.

A head-to-toe physical exam is also important. If this doesn't turn up any clues to the weight loss, the doctor will order lab tests, including:

  • Complete blood counts
  • A blood test for inflammation (erythrocyte sedimentation rate or C-reactive protein)
  • Blood chemistries, including liver and kidney function tests, a blood sugar level, thyroid function tests, and calcium and serum electrolyte levels
  • Urine test
  • Tests for blood in the stool
  • Chest X-ray

If these tests are inconclusive, one reasonable option is for the doctor to keep a close eye on the patient's weight and symptoms for three months, then repeat the first round of tests to see if anything has changed.

Another tactic is for the doctor to order more elaborate testing, which may include CT scans and evaluation of the GI tract. There is no evidence that aggressive testing is helpful unless there are clues pointing to specific problems. Sometimes, in fact, the best approach is patient, careful observation. Or, as the old slogan says, "Don't just do something, stand there."

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Gaining Back the Weight

It's hard to take off excess pounds. And it's also hard to put back pounds that have been lost involuntarily. The best results occur when doctors can fix the problem causing the weight loss by:

  • Regulating thyroid function
  • Replacing defective dentures
  • Treating depression
  • Controlling a malignancy
  • Stopping a medication that's doing more harm than good

If there is no way to fix the original problem, the goal is to prevent further weight loss. Nutritional counseling may encourage a person to eat more calorie-dense foods, frequent small meals, and foods with appealing textures and flavors. Community organizations can help with shopping and providing meals. Social supports may enable people to eat with others, which often boosts caloric intake.

Nutritional supplements, such as Ensure and Boost, will provide extra calories between meals that people need to gain or maintain weight. Although vitamins will not add pounds, a multivitamin may help make up for nutritional deficiencies.

Finally, while exercise is a crucial component of weight-loss programs, it can also help with weight gain by building muscle mass and stimulating appetite.

Although there seems to be a pill for nearly everything, medications are not very effective for weight gain (or, for that matter, weight loss). In special circumstances doctors may prescribe a steroid hormone (such as a stress hormone in the cortical family, a male hormone in the testosterone family, or a female hormone in the progesterone family), but there is little evidence they help in the long term. And side effects are common.

Many people envy others who are trying to gain weight. Be careful of what you wish for; involuntary weight loss may reflect a serious underlying problem, and even if it doesn't, gaining weight can be a struggle.

Bouras EP, et al. "Rational approach to patients with unintentional weight loss." Mayo Clinic Proceedings. 2001; 76:923.

Rolland Y, Kim MJ, Gammack JK, et al. "Office management of weight loss in older persons." American Journal of Medicine. 2006; 119:1019-1026.

McMinn J et al. "Investigation and management of unintentional weight loss in older adults." British Medical Journal. 2011; 342:d1732.

Wannamethee SG et al. "Reasons for intentional weight loss, unintentional weight loss, and mortality in older men." Archives of Internal Medicine. 2005; 165:1625.

Wannamathee SG et al. "Weight change, weight fluctuation, and mortality." Archives of Internal Medicine. 2002;162:2575.

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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.

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