Updated 18 June 2013

Unintended weight loss could spell danger

Losing weight even though you don't want to? Sudden, unexplained weight loss could be an indication of a serious underlying illness, warns DietDoc.

The majority of people who consult me are frantic to lose weight. However once in a while a member of the public will mention that he or she is concerned because of unintended weight loss. Such individuals usually start worrying, and rightly so, that something may be wrong.

In some cases caregivers responsible for elderly parents or young children or even teenagers become concerned when their charges lose weight suddenly. In all these cases it is important that the person who is losing weight should be examined by a medical doctor to determine if there is an underlying physical cause of the weight loss.


It is important to determine if the person losing weight has not changed one or more factors in their routine which could explain the weight loss. For example a patient who has taken medications for a short-term illness or condition may lose some weight if the medications suppress appetite unintentionally either because of their chemical effects on the absorption of nutrients or on the patient’s sense of smell and/or taste. This phenomenon should, however,  end either when the medication is stopped or shortly thereafter.

How truthfully the person who is losing weight is reporting on changes in diet, food intake and exercise patterns must also be assessed. Teenagers developing anorexia, bulimia, orthorexia or any other eating disorder, can be highly adept at concealing the fact that they are either not eating, or inducing vomiting or purging, or exercising to exhaustion. It is not uncommon for parents, teachers, coaches, and other persons tasked with overseeing the diet of adolescents to be the last to know that the young people in their charge have developed an eating disorder.

Conditions that may cause unintended weight loss in adults

There are a surprising number of conditions that are associated with unintended weight loss both in adults and in children. For today we will consider some of the conditions that can result in pronounced weight loss in adults, namely:
  • Psychological conditions which include anxiety, depression and stress. Although antidepressants are usually effective in halting unintended severe weight loss, some of these medications may also cause weight loss (see below) even while they combat the depression
  • Various cancers, particularly of the digestive tract (mouth, oesophagus, stomach, bowel)
  • Coeliac disease due to gluten sensitivity. Gluten occurs in wheat, rye, oats, barley, spelt, kamut, titricale and all processed foods that contain these grains or their derivatives
  • Diabetes - many patients with sudden weight loss also exhibit the classical symptoms of increased urinary frequency and thirst indicative of polyuria
  • Problems with chewing - as people age they may develop problems with their teeth, production of saliva, swallowing and sense of taste and smell
  • Hyperthyroidism or overactive thyroid can lead to such an overproduction of thyroid hormone that patients have greatly increased energy requirements
  • Inflammatory bowel disease which includes Crohn’s disease, diverticulosis, or post-antibiotic Clostridium difficile infection
  • Intestinal ischaemia where the blood supply is reduced or cut off to part of the intestines thus damaging the small intestine, the colon or both. Acute intestinal ischaemia is a medical emergency requiring immediate surgery. Chronic intestinal ischaemia can lead to inability to digest and absorb food which then results in weight loss
  • Medications such as antidepressants, anti-inflammatories, anticancer drugs, bronchodilators, heart drugs, stimulants and in some cases even contraceptives or hormone treatments can cause weight loss. The role played by any medications (prescription and over-the-counter products) a patient may be using, should always be taken into account when evaluating unintended weight loss
  • Nausea and vomiting which can be due to infections, food allergies, hormonal changes (pregnancy is a common condition that is associated with nausea or ‘morning sickness which if extreme can lead to severe weight loss), and medications (for example antibiotics)
  • Pancreatitis and cystic fibrosis which reduce the production of enzymes required for digestion of food.
(Mahan et al, 2012)

It is evident that most of the conditions that can be associated with pronounced weight loss are of a serious nature and require both medical and nutritional interventions. It is, therefore, essential that anyone who is suffering from unintended weight loss should first be assessed by a medical doctor to determine if the trigger for the weight loss is a serious underlying disease such as cancer, diabetes, Crohn’s disease, severe depression, pancreatitis, or coeliac disease to name but a few.


Each one of the above mentioned medical conditions requires treatment, for example prescription of medications (which also need to be monitored for a tendency to cause weight loss as illustrated by the depression-antidepressant interaction which can both lead to undernutrition which was mentioned above) and in certain cases also surgery (removal of tumours, necrotic bowel tissue, etc).

Once a medical diagnosis has been made and treatment is instituted, patients also require nutritional support. It stands to reason that someone suffering from cancer of the digestive tract will require a different diet to a patient with coeliac disease. In the majority of cases of unintentional weight loss, patients should therefore also consult a registered dietician for a high-energy diet that addresses their specific problem to encourage weight gain.

The use of high-energy liquid meal supplements can be considered, but inclusion of additional standard foods to the diet can also be a successful way of increasing daily energy intake in patients without serious underlying diseases. Your dietician will help you add extra energy foods to your menu.

Example of how to add 4200 kJ to your daily energy intake:

According to Mahan et al (2012) the addition of the following foods which can be served between meals will boost your energy intake by 4200kJ or 1000 kcal per day:
  • 250 ml fruit-flavoured, sweetened yoghurt made from full-cream milk: 1000kJ
  • 1 slice of brown bread (30g), with 50g of Cheddar cheese: 1200kJ
  • 1 apple (160g): 400kJ
  • 1/4 cheese pizza (120g): 1200kJ
  • 1 medium banana (100g): 400kJ
    Total: 4200 kJ*

The quantities of food listed above are not excessive and it should be possible to fit them in to your daily menu without replacing existing foods. Eat such additional foods as snacks and in between meals to boost your energy intake without scrimping on your regular meals.

Other factors such as relaxing and making mealtimes enjoyable instead of just grabbing a cup of coffee on the run, can also contribute to better appetite and food intake. It is important not to skip meals, so be strict with yourself to ensure that you can regain the weight you have lost unintentionally. Maintaining a normal weight also contributes to general good health and reduces your risk of mortality.

So if you or a member of your family, especially older adults, have suddenly lost weight without going on a slimming diet or joining a gym, then you need to see a doctor and a dietician and start getting back to a normal weight as soon as possible.

*Energy content based on average rounded values obtained from Wolmarans et al (2010)
(References: Mahan LK et al, 2012. Krause’s Food and the Nutrition Care Process. 13th Edition. Elsevier; Wolmarans P et al, 2010. Condensed Food Composition Tables for South Africa, Medical Research Council, Parow Valley, Cape Town.)

- (Photo of worried woman from Shutterstock)

Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Read more of her articles.


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