Why the US Preventive Services Task Force Missed the Boat on BMI

Tuesday, July 3, 2012

Last week, the US Preventive Services Task Force issued the following recommendation for the screening and management of obesity in adults aged 18 years or older:

“Screen for obesity. Patients with a body mass index (BMI) of 30 kg/m2 or higher should be offered or referred to intensive, multicomponent behavioral interventions.”

This recommendation was supplemented by the thoughtful advice, that obese adults should be offered

“Intensive, multicomponent behavioral interventions for obese adults include the following components”:

  • Behavioral management activities, such as setting weight-loss goals
  • Improving diet or nutrition and increasing physical activity
  • Addressing barriers to change
  • Self-monitoring
  • Strategizing how to maintain lifestyle changes

It is hard to even know where to begin criticizing these recommendations for their inadequacy, inaccuracy, and likely inefficacy.

Never mind that BMI is woefully inadequate in diagnosing individuals who actually have health risks related to their body fat. As regular readers, familiar with our papers on the Edmonton Staging System will be well aware, BMI substantially over-diagnoses ‘obesity’ in those with a BMI greater than 30 while missing millions with body fat-related risk in the BMI 25-30 range.

My recommendation would have been as follows:

“Screen everyone for BMI. In those with BMI greater than 25, screen for obesity related health problems (i.e. determine obesity stage). If problems are found (Stage 1+), consider obesity treatment; if not, then screen them again in a year or so.”

As for the treatment recommendations – how exactly is ‘setting a weight-loss goal’ a ‘behavioral management activity’?

For one, losing weight is NOT a behaviour – it is behaviours that may (or may not) lead to weight loss. Eating breakfast is a behaviour, walking to work is a behaviour, getting more sleep is a behaviour, passing up dessert is a behaviour – losing weight is not.

Secondly, what is it with setting weight-loss goals? Isn’t that the very antithesis of what obesity management should be about. Here we preach that obesity management should be about improving health and well-being rather than simply moving numbers on a scale (see the 5As of Obesity Management) – the Preventive Task Force thinks it is better to focus on a weight-loss goal – go figure!

And what about the recommendation regarding, “Improving diet or nutrition and increasing physical activity”. How do I even know that there is room for improvement, before I have even bothered assessing nutrition or physical activity. Of course, the Task Force simply assumes that if your BMI is greater than 30, then there certainly is room for improving your diet and activity – because, after all, anyone with a BMI greater than 30 probably has a miserable diet and sits on the couch all day (I cannot help wonder what a test for weight bias amongst the Task Force members would reveal).

At least ,”Addressing barriers to change”, certainly sounds good – until you realise that this is not directed at recognising mental health problems, socioeconomic challenges, obesogenic medications or sabotaging spouses and co-workers – no, this is about addressing ‘barriers’ in those with a BMI greater than 30, who don’t want to or don’t happen to see the need to ‘change’ (perhaps simply because they’ve been through this before?).

While I am not going to argue with ‘self-monitoring’, I am far less certain about, ‘Strategizing how to maintain lifestyle change’, largely because I do not like the underlying assumption here, that the problem is simply a matter of ‘lifestyle’.

The very use of the term ‘lifestyle’, not only trivialises the problem (oh, it’s simply a matter of changing my lifestyle – why did you not mention that before – now, that’s easy!) but it also implies that it only takes a change in ‘lifestyle’ for my BMI to drop below 30. Really, all I need now, is a ‘strategy’ and we can all live happily ever after.

Interestingly enough, the recommendations actually go on to discuss ‘Harms and Benefits’:

“Adequate evidence indicates that intensive, multicomponent behavioral interventions for obese adults can lead to weight loss, as well as improved glucose tolerance and other physiologic risk factors for cardiovascular disease.”

That may well be and no one would argue with the potential for these interventions in helping obese adults lose weight – the problem, however, is never losing weight – the problem in obesity management is keeping the weight off. Thus, it may have behoved the Task Force to perhaps mention the importance of long-term management to avoid relapse or recidivism – no indication, either, that sometimes, prevention of further weight gain may well be a reasonable and feasible outcome.

“Inadequate evidence was found about the effectiveness of these interventions on long-term health outcomes (for example, mortality, cardiovascular disease, and hospitalizations).”

If this is indeed true (and I agree, the data on this are limited), then why would you even recommend these interventions to everyone with a BMI over 30 – especially those, who do not appear to have any health problems and are therefore at low risk of mortality, cardiovascular disease and hospitalizations in the first place? (as an aside, the only data on reducing ‘hard endpoints’ with obesity treatments that I know of, come from pharmacological and surgical treatment of obesity in high risk patients – not from ‘intensive, multicomponent behavioral interventions’.)

“Adequate evidence indicates that the harms of screening and behavioral interventions for obesity are small. Possible harms of behavioral weight-loss interventions include decreased bone mineral density and increased fracture risk, serious injuries resulting from increased physical activity, and increased risk for eating disorders.”

So fractures, injuries and risk for eating disorders are the only harms of screening and behavioural interventions? What about frustrations, depression, lower self-esteem, body image issues, and weight cycling? And what about the economic loss from spending good money on useless ‘eat-less-move-more’ strategies?

Often less is more – in this case, not having bothered to release these rather useless ‘recommendations’ would certainly have been More (with a capital ‘M’).

AMS
Edmonton, Alberta