The cause of the weight loss is complex. It’s partly due to loss of appetite resulting from the disease itself or the nausea and vomiting that can accompany chemotherapy.
However, loss of appetite alone cannot explain the weight loss. Complex metabolic changes occur when patients suffer from cachexia and to some extent they are irreversible. Patients suffering from malnutrition can reverse their weight loss but not those suffering from cachexia.
The precise mechanisms of cachexia are complex, and not totally understood. Patients experience an increase in resting energy expenditure (REE), i.e. they burn more calories at rest causing a tissue breakdown in order to supply the energy needed. Rising levels of cytokines like tumour necrosis factor alpha (TNF-alpha), imterleukin-1 and interleukin-6 have all been proposed as possible culprits, although it is likely that no single agent is responsible and that the cause is due to the complex interplay of many molecules.
While cachexia is more common in lung, prostate, kidney, and gastrointestinal cancers, in reality it is hard to predict who will develop the condition, which, in any case, is difficult to treat in and of itself, with the best course of action being control of the underlying disease as was done with AIDS. With the development of improved anti-retrovirals for HIV, the wasting syndrome seen with AIDS patients has largely disappeared, and patients with suppressed viral loads (i.e. no detectable virus in their blood) do not develop this condition.
Various medications like steroids and hormonal agents have been tried in order to stimulate the appetite and treat cachexia but the response has been mixed. Steroids in particular show some short-term benefit and do seem to increase appetite, but they don’t have an important effect on weight gain nor do they improve survival.
Cannabis is commonly referred to as a possible appetite stimulant, often reflected on TV and in film. In actuality, what little data exists shows that it has some effect in treating the nausea associated with chemotherapy, which in turn may lead to weight gain, but the trial data has been disappointing.
In conclusion, other than treating the underlying disease (as stated above), of course the best way to avoid cachexia is to prevent it entirely by way of commonly familiar health admonitions, i.e. tobacco avoidance, regular exercise, and a healthy diet.
Additionally, advances in medical technology as well as the population in general leading a healthier lifestyle in accordance with these principles means that cancer rates and mortality continue to decrease.
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