OB_S__Y is a cause of cancer
March 24th, 2018
Author Dr Joshua Wolrich
Is Obesity a cause of cancer?
As the Scientific Editor for Nutritank, I thought it would be apt to share with you my thoughts on the recent Cancer Research UK campaign. For those who aren’t aware, Cancer Research UK recently launched a campaign to raise awareness between weight and cancer. They have also released a bunch of graphics explaining why they are saying that being obese causes cancer. Twitter then blew up as CR UK was accused of ‘fat shaming’ by plus-sized comedian Sofie Hagen.
Being obese (let’s not get hung up on the nomenclature, we can talk about the limitations of BMI another time) is correlated with a higher risk of having a stroke, heart disease, liver disease, type 2 diabetes and certain types of cancer, as well as many other health conditions. Some of these correlations are much stronger than others.
Correlation isn’t the same as causation. Having said that, cancer is famously hard to find causes for. Being a disease of many forms, and also one that often takes many years to actually develop, studies are often used to associate risk rather than specifically attribute cause. Does that mean we should throw the baby out with the bathwater and ignore the correlations? In my mind, absolutely not. Smoking was correlated with lung cancer long before we found the physiological mechanism that led to that changing to causation. Does that mean that the correlation shouldn’t have been talked about?
Issues with the Campaign
The infographics state that “obesity causes 13 types of cancer”. As explained above – the worse ‘cause’ is inappropriate.
It mentions nothing of ABSOLUTE risk (how common that cancer is full stop) vs. RELATIVE risk (how much more likely you are to get that cancer if you are obese). The absolute risk is going to vary from cancer to cancer, one example using Australian data is that the risk of getting endometrial cancer if a woman is obese is twice that of her non-obese counterpart. Sounds bad right? Well that RELATIVE risk of ‘100% greater chance’ is actually only a difference from 2% to 4% when we look at ABSOLUTE risk. Still bad, but not as bad as the figures can initially sound.
People have raised concerns that the campaign further stigmatises fat bodies. Despite CRUK not intending it to be interpreted this way, is it important to consider. Weight stigma has been shown to be associated with an increased risk of binge eating disorder, reduction in engagement in healthy eating and physical activity, and increased physiological stress responses. I believe it’s sad that as a society we have created a situation where sometimes it doesn’t matter how we talk about it, just the act of talking about it is a problem – we have to figure out how to fix this. Fat-shaming is, and always has been, unacceptable. Being fat doesn’t make you less of a person, doesn’t make you less incredible, doesn’t make you less loved.
Issues with the Public Response
I keep seeing “healthy at every size” being mentioned. This is a dangerous assertion and not backed be science. A study last year found,
“Out of the 3.5m participants, who were initially free from cardiovascular disease, about 15% were classified as metabolically healthy obese. During an average follow-up period of five years, of the people who were initially metabolically healthy obese, about 6% developed diabetes, 12% had abnormal blood fats and 11% developed high blood pressure. Compared with normal weight people with no metabolic abnormalities, people who were metabolically healthy obese had a 50% increased risk of coronary heart disease, a 7% increased risk of stroke and a double risk of heart failure [using hazard ratios]. These results couldn’t be explained by age, sex, smoking or socioeconomic status as we took these factors into account in our calculations.”
Due to the fact that losing weight has been shown to reduce the risk of certain health conditions (including cancer), it would be stupid to disregard all of the available research just because solid causative reasoning hasn’t been found yet. I wish people would stop doing this… but on the other side of the coin we need to be careful drawing TOO much conclusion from weak correlation. In this situation though we are not talking about weak correlations.
Should we be raising awareness about all of this? Yes. Is the easy option just to condemn the campaign? Yes. Could the CRUK campaign have been better thought out? Maybe.
Share this post!
SUBSCRIBE TO OUR MAILING LIST
Keep up to date with all of the latest information and news around food, nutrition and lifestyle.