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The risks of weight loss during cancer

Screenshot 2022 05 29 at 23.22.29

Cancer patients with obesity advised not to lose muscle during treatment 

Cancer treatment ‘not the time’ to lose weight or muscle 

Half of adults are unclear about whether nutrition makes a difference during cancer care, and 60% don’t know that losing weight or muscle during treatment carries risk, including for patients who are overweight or obese.

A RED C survey commissioned by theIrish Society for Clinical Nutrition and Metabolism (IrSPEN), on a representative sample of 1,000 adults, found concerning levels of misinformation and misunderstanding around the importance of nutritional status during cancer care, despite the fact that one in two of us will develop cancer.

The research found:

  • More than half of people (56%) are not clear on the importance of nutritional care during cancer treatment, with one in four thinking that good nutritional intake was not crucial
  • 28% of people incorrectly believed that if a person is overweight or obese, losing weight is a positive side effect of cancer with a further 32% unsure
  • A majority (53%) were not clear that maintaining muscle mass and strength is important for patients undergoing treatment for cancer
  • 36% of people incorrectly believed or were unsure that overweight cancer patients would be ‘unlikely’ to require nutritional care (screening, advice, monitoring and access to dietitians).

IrSPEN spokesperson and Obesity Specialist at St Vincent’s University Hospital Professor Carel le Roux said current medical research shows that maintaining good nutritional health, body weight and muscle mass during cancer care significantly improves medical outcomes – including for people with overweight or obesity.

“Losing weight without trying and losing muscle mass are common problems in cancer – affecting at least one in three of patients. Contrary to what people seem to think weight and muscle loss are unhelpful at the time of treatment – whether people are under or overweight – making treatment less effective and increasing the risks of complications.

“From the time of diagnosis and during active treatment, the goal is to minimise weight change, preserve muscle mass and maintain body strength.”  

“It is of concern that the RED C survey shows that patients with obesity may be particularly at risk of not receiving the care they need due to a misconception that losing body mass is a positive side-effect of cancer.”

Professor Le Roux said that this is important for many people, as 40-60% of cancer patients are overweight or obese at the time of diagnosis. 

“Before or during active treatment is not the time for weight loss, including for people with obesity, as it may negatively impact the patient’s response to treatments and make them more susceptible to complications that can result in having to delay further treatment, which can affect overall survival. There is a time for achieving weight loss in patients with obesity, but this is not while undergoing cancer treatment.

“As clinicians we need to pay greater attention to relatively modest changes in body weight and muscle mass, since the earlier we can catch it, the more effective we can be in preventing cancer related malnutrition.

IrSPEN President and Consultant Gastrointestinal Surgeon Professor John Reynolds said there is a need to dispel the myth that weight loss and deterioration in nutritional status is an inevitable consequence of cancer and its treatments.

“High quality cancer care would benefit from a greater focus on the patient’s nutritional status, which is why IrSPEN continues to push for more specialised dietitians in cancer care and mandatory routine nutrition screening for outpatients receiving cancer treatments, not just inpatients. 

“It important to understand that weight loss and malnutrition are not inevitable or something that can be dealt with after treatment. An important pillar of cancer care is to keep the patient in the best possible condition to benefit from the advances we have seen in treatments.” 

Specialist Oncology Dietitian, Veronica McSharry, said that by the time many cancer patients are referred to her for help, they are already severely malnourished.

“Failure to address nutritional deterioration in cancer, including in those who are overweight, puts the patient at risk of poor tolerance to chemotherapy, increased complications in surgery and increased need for hospital inpatient care. 

“We would like all patients to be screened for signs of developing malnutrition at every hospital outpatient visit and treatment setting, so that we can intervene early with patients who are unable to eat enough to maintain their weight and muscle mass.”

Ms. McSharry said that once cancer patients’ nutritional needs have been identified they can be addressed effectively.

We can advise on changes to make to dietary patterns, provide treatments for digestive issues, incorporate extra protein or nutrients into foods or recipes, or prescribe protein and energy supplements for those who cannot manage to eat enough. Tube feeding or even intravenous feeding options are available for patients with more complicated issues. Nutritional problems can be challenging but can be addressed. 

“We need greater awareness not only among people suffering from cancer and their families, but also those involved in providing cancer care that addressing nutrition problems will benefit the patient.

“The message for all cancer patients irrespective of their weight is – if you are unable to maintain your weight and experiencing noticeable loss of muscle, seek advice from your care team and / or request a referral to a Dietitian and the earlier the better.”



Further Information

Ronan Cavanagh, Cavanagh Communications: (086) 317 9731 /

About IrSPEN

The Irish Society for Clinical Nutrition and Metabolism (IrSPEN) is a multi-disciplinary professional organisation dedicated to optimising screening for and management of those at risk of malnutrition or other nutritional problems in Ireland, whether in hospital or in the community.

Founded in 2010 with the support of the Irish Society of Gastroenterology (ISG), the Irish Nutrition and Dietetic Institute (INDI) and the Irish Section of the Nutrition Society, IrSPEN members are clinicians, dietitians, nutritionists and other health professionals from clinical practice, research and education. Together our aim is to combat malnutrition by optimising the nutritional management of patients in hospital and the community.


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