Confused about cancer and body weight? You will be.

Considering the number of cancer awareness days, weeks and months, and the ubiquity of human interest cancer case studies in the popular press, you’d think the public would be filled up to here with comprehensive knowledge about cancer. Not so.

A recently published report “Public Awareness of Cancer in Britain” produced under the auspices of the Department of Health, with support from cancer charities and academe via the National Awareness and Early Diagnosis Initiative (NAEDI),  showed something quite different.
The public has great trouble recognising the commonest risk factors. Recalling them unprompted was even worse. Around about three quarters of people surveyed didn’t recognise that too much alcohol, too much meat and too little fruit and veg. were significant risk factors for cancer. A larger proportion failed to recognise lack of exercise was, too. In spite of the media obsession with obesity only half the people surveyed recognised overweight as an issue.
The ones you can change are clearly the ones you’d like as many people as possible to recognise. This isn’t going to plan. At all.  
Of course, recognition of a risk factor does not necessarily translate into action to modify it. If it did, smoking would no longer be an issue, but NAEDI are going back to the messages to see if it’s possible to make them work better. Consistent, readily available, clear. That kind of thing.  
Cancer charities always have messages, often health promotion ones. As a group they see themselves as leaders in awareness raising. It helps if their messages are consistent, readily available, clear, that kind of thing, especially as what the charities say often pops up in media coverage.
One cancer charity has caught my eye because of their messages. Mostly, it’s OK. But not all of it. They introduce the ambiguity that can muddy the waters of health promotion. It’s difficult to judge their profile, so what they have on their website may not matter if no one reads it, but they are behind some really useful science based cancer stories that come out now and then. Their schtick isn’t lessons from brave people overcoming cancer but a rather more objective ‘prevention of cancer’ message.
But I am already leaning forwards, ready to grumble.
It's true that “about a third of cancers could be prevented by eating a healthy diet being physically active and maintaining a healthy weight.” Whilst this is a fact, it is incorrectly translated into a 'prevent cancer' message for individuals. What they mean is 'you can reduce your risk' which isn't the same thing at all. They have elided a population based truth -  that it is possible to prevent some cancers -  into a half truth to make it a message for individuals. 
By making some lifestyle changes you can reduce your personal risk of getting some kind of cancer diagnosis, by one third. I do the 'right' lifestyle things, but the risk of me getting a non-lifestyle related cancer, which cause the other two thirds of cases, remains stubbornly unchanged. Besides even though I am a 'never smoker' this will not prevent me getting lung cancer – it has certainly reduced the risk very considerably, but that's the best it can get.  
Unsurprisingly, much of their messaging is about diet, weight and exercise. All mostly very appropriate and, you’d think, easy to be clear about, but again I find the message unhelpful.
On the Body Mass Index (BMI) they a give a standard account of its meaning and interpretation  - “BMI gives an indication of body weight based on the height and weight of adults. A BMI chart normally consists of four ranges: healthy, underweight, overweight and very overweight or obese.”
That’s clear but then very next sentence implies something slightly different. “For cancer prevention, we should aim to be as lean as possible without becoming underweight." So there’s a healthy weight and then there’s another kind of extra healthy weight, one that prevents cancer. I don't dispute the scientific background of this (if it's cobbled togther from mouse studies I will, but that's an issue for another day) but I do dispute the naive attempt to translate allegedly applicable science straight into people. 
Crowbarring the science of leanness straight into health promotion for the masses is daft. The big problem is with overweight and obesity, not the wrong kind of thinness. The message on overweight is the one the public need to hear consistently, not this finessing at the thin end.
According to the Health Survey for England only about 2% of the population have a BMI of 18.5 or less, so getting as close as you can to that without dropping over the edge is the wrong ambition. It's the 61% with overweight and obese BMIs who have a big problem with the risk of cancer. It's also daft because achieving a lean body weight safely is impossible without close expert supervision. It's also daft because the message itself is unadulterated science, with no attempt to make it into a manageable or achievable ambition for anybody - as if the general public will be knocked into shape (literally) by the force of objective evidence. There's no particular knowledge of health promotion or social marketing, or even high street advertising tricks on display by this health promotion charity. Ow!
I explore further. “A healthy BMI for both men and women is between 18.5-24.9. For cancer prevention, we should aim for the lower end of this range.”
For the purposes of illustration I include my own figures.
I weigh 133 lbs and am 5 ft 2ins and their BMI calculator awards me a BMI of 24.3 i.e. healthy. I’ve been ‘healthy’ for years now. I used their BMI calculator to work out what my weight would be at the ‘nearly but not actually’ underweight end of the spectrum. The answer is for a BMI of 18.5 I should be 101 lbs -that's 7 stone 3lbs. A massive 32 lbs less than I weigh now. Just picking that one weight might be a somewhat harsh interpretation of their meaning, though it does match their wording -  so, if I give myself a more realistic range of weight for ‘lean’ e.g. the bottom 25% of the healthy fraction, that gives me a weight of 101 to 109 pounds to play with.
So I’m still, at best, 24lbs on the wrong side of my cancer risk.
I am not going to try and become 101 lbs, or 109 lbs. Me trying to weigh in somewhere between 7 stone 3lbs and 7 stone 11lbs represents being thin and ill to me, my body, my friends and my relatives. I can’t envisage attempting it without developing a joyless relationship with food, maybe an eating disorder and a social life that will be fine as long as it never includes the phrase “let’s go out for a meal”. “A bite to eat” might be possible. Only a bite, mind.
And then there's the added exercise I'd need to do on the way to seven and a half stone. As I'll be exercising a lot to get my weight down, my BMI would be a less accurate measure of my leanness - and it's leanness I'm attempting to influence in this skinny dystopia. If not BMI, what is the quick, easy and accurate way of checking I'm healthy and on track?
I expect there are added risks for me, at 50, for attempting that level of weight loss, however slowly and responsibly, as I step into my menopausal twilight.  I’m certainly not seeking any menopausal limelight – far too harsh for my far too thin face. If I'm too old, I’m not sure a women of child bearing years should attempt it either. When exactly does weight maintenance at that level eat into your ability to conceive a baby and carry him or her healthily to full term? How about even younger women - weight ambitions of that type in a teenage girl really does sound like clearing the way for full on anorexia nervosa.
Plainly, it isn’t clear to me for whom being ‘as lean as possible without being underweight’ is a wise or achievable ambition, given all the other things in the equation that make up a healthy lifestyle and a balanced diet. A State Registered Dietician might be able to do it safely, and remain well. I wonder if they would? Or do?  
I’m sure I couldn’t. I’ve settled at a healthy weight. Can’t I just stay there? 
Is my failure  to even fleetingly consider attempting such weight loss a moral failing, complacency or ignorance or a reasonable trade off between idealistic and realistic? Have I simply drawn a line in the sand beyond which my fear of cancer is simply not going to push me, the fear that charities work so hard to keep at the front of our minds?
So, as the public muddle on about modifiable risk factors it will be interesting to see if NAEDI can tease out how much of the muddle originates with the ‘experts’ who think they are sorting it out.
The messages I’m puzzling over come from the World Cancer Research Fund. It’s even a muddled name with no mention of their core activity of ‘prevention'. ‘Cancer research’ is not a hitherto unrecognised synonym for it.
Not enough cancer research is in prevention but that’s another issue entirely.