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Unintended weight loss

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 4 minutes read

It’s common to experience a lack of appetite at various points in life, and this often leads to shedding a few pounds. Times of extreme emotional stress, bereavement, or illnesses such as flu or gastroenteritis are common reasons. But it can cause alarm if you can’t see a reason for it, and it can be distressing to feel clothes becoming baggy or have people commenting.

Worries can be parked in two camps: firstly, how much weight you’ve lost and the risk of malnutrition, and secondly, whether there is any serious medical condition causing the weight loss.

When to worry about weight loss?

If you are of slim build or in the lower healthy range of body mass index (BMI), you might notice weight loss more quickly than others with a higher BMI. As a rule of thumb, it’s concerning if you lose more than 5% of your body weight in less than six months, without adjusting your diet or exercising more, or because you suddenly have a reduced appetite. If the weight of the average man is 155 pounds, this is about 8 pounds.

You may feel less hungry, be full more easily, or you may be eating the same amount but still losing weight. You’re likely to feel quite tired and drained of energy and more intolerant of the cold. You may start losing hair, periods may become irregular or absent in women, and you may develop specific problems if you are deficient in certain vitamins and minerals.

What about other symptoms?

You should see your doctor with significant weight change, or if there is some weight loss and other particular symptoms. Reduced food intake can cause constipation in itself, or even overflow diarrhea, but this may be a reason for further investigation, particularly if you experience any bleeding from the rectum.

For those less than 40 with a relevant family history, this may suggest Crohn’s disease, ulcerative colitis, or celiac disease. For those over 50, bowel cancer may need to be considered.

If you are a smoker and experience weight loss and a cough persisting for more than three weeks without other signs of a chest infection, or you have blood in the sputum, see your doctor, as they will need to consider lung cancer.

Thyroid problems are common – an overactive thyroid (hyperthyroidism or Grave’s disease) can cause weight loss despite normal or increased appetite, plus other symptoms like insomnia and palpitations.

Elderly people tend to lose their appetite and may experience weight loss. In those less able to articulate themselves, it’s important to determine if there are problems swallowing, any symptoms including bowel problems, depression, dementia or other lifestyle factors, or difficulty shopping or preparing food.

Ongoing infections such as hepatitis in the liver, HIV and AIDS, or bacterial or parasitic gut infections also need to be considered.

Could it be an eating disorder?

Eating disorders such as anorexia nervosa and bulimia nervosa can result in weight loss, alongside other methods of calorie control, such as excessive exercising and the use of amphetamines or laxatives. This can occur in all ages and both sexes, but women and girls are most commonly affected. It may accompany a lack of self-esteem, self-confidence, anxiety, and depression.

If you are concerned about yourself or a loved one, it isn’t easy to make the first move to recovery, but understanding more is the first step. Do book an appointment with your doctor to discuss this. They can offer advice and consider any tests needed, and refer you to services to support you.

How can I look to regain weight?

Weight gain should be a gradual process, where calories are sought from healthy sources that release energy slowly, such as whole grains, oats, nuts, and legumes. It may help to have smaller, more frequent meals or snacking between meals. The immediate sugar high that cakes, biscuits, sweets, and chocolate provide is not ideal, as they can create new problems such as tooth decay and a longer-term risk of diabetes and heart disease.

You should speak to your doctor if you or a loved one is losing weight so this can be assessed and investigated. You may need certain vitamin supplements. A dietician’s advice may be sought, and they occasionally recommend meal-replacement drinks if not enough calories can be gained from the diet.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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