Is this the case for all cancer patients?"

Not all cancer patients lose a lot of weight. In fact, there are some cancers that result in weight gain during treatment. Certain types of chemotherapy, hormone therapy and medicines, such as steroids, can cause the body to retain fluids or increase a patient’s appetite so that they eat more, causing weight gain. However, for many patients the type of cancer and its treatment make it hard for them to eat well enough to take in all the nutrients required to maintain weight. A patient may seem to be eating enough, yet can still lose weight. 

Cancer and cancer treatments can affect taste, smell, appetite and the ability to eat enough food or absorb the nutrients from food. Malnutrition is common in people with cancer and occurs when there’s an imbalance of energy, protein or other nutrients. 

Malnutrition can reduce a patient’s strength, function and quality of life. If a cancer patient is not able to eat their usual amount of food, or needs to gain or maintain weight, it is helpful to take in more energy (kilojoules) without having to eat more. Adding extra protein, fats and sugar at mealtimes, or nutritional supplements, may help maintain weight. A patient’s doctor or dietitian can help with dietary advice.