Thursday, January 31, 2013

The New England Journal's Obesity Mythbusting

Yesterday an article authored by a veritable who's who list of obesity researchers was published in the New England Journal of Medicine. Titled, "Myths, Presumptions, and Facts About Obesity", it details what the authors describe as seven popular obesity related "myths", six common "presumptions", and nine understated evidence supported "facts".

While I agree almost wholeheartedly with the "Facts" section, and agree too that the "Presumptions" (presumptive in that we don't have enough data yet to decide one way or the other if they're true) are indeed still presumptions, I'd argue some of the "Myths" have yet to be busted.

For what they're worth, here are the myths, presumptions and facts and my thoughts occasionally interspersed therein.

The Myths

These are subjects that the authors feel have sufficient data to conclusively dismiss them as false. While I agree in some cases, I don't in all. That doesn't necessarily mean the authors are wrong and that I'm right, just that our opinions differ:

1. "Small sustained changes in energy intake or expenditure will produce large, long-term weight changes".

(Agree this is a myth. Putting this another way, I'll often tell my patients weight loss is insert-adjective here. Meaning small changes only lead to small losses and if you want to lose a huge amount of weight, you'll need to undertake (and sustain) a huge amount of change.)

2. "Setting realistic goals for weight loss is important, because otherwise patients will become frustrated and quit".

(Disagree. Not that the statement's true or false, just that the authors call it a myth consequent to the fact that there isn't robust evidence proving it to be true or false. Until there's robust evidence one way or the other, tough to call this one a myth and I'd have put it into their "presumptions" section. Moreover, tough to apply to everyone as no doubt some people likely respond wonderfully to aggressive goals, while others quit consequent to not reaching a dream destination.)

3. "Large, rapid weight loss is associated with poorer long-term weight-loss outcomes as compared with slow, gradual loss".

(Disagree. Here again is an area where I don't think we have sufficient data. The authors refer to year-long studies as long term data and frankly I don't think that's long term. For instance if a person rapidly loses 80lbs during an 8 month meal-replaced, very-low-calorie-diet looking at 1 year as "long term" only gives that person 4 months to regain. So I'd argue anything less than 2 year data is a short-term outcome and that we need data from at least 2 or more years out to draw long term conclusions and that's truly rare to come by.)

4. "It is important to assess the stage of change or diet readiness in order to help patients who request weight-loss treatment"

(Disagree. Here the authors report that studies that have looked at stage of change in people voluntarily entering weight loss programs didn't predict outcomes. Yet as the authors themselves point out, by definition folks voluntarily choosing to enter weight loss programs are at least minimally ready to face change. But for the clinician working their primary practice and not a practice like mine for instance, no doubt stage of change assessment crucial - if not for success than certainly for a respectful doctor patient relationship.)

5. "Physical-education classes in their current form, play an important role in reducing or preventing childhood obesity"

(Here all I can say is AMEN. No doubt evidence very clearly suggests kids aren't going to burn off or prevent obesity by means of school based PE classes.)

6. "Breast-feeding is protective against obesity"

(The authors report that a WHO meta-analysis on the subject was flawed, and that well controlled trials failed to demonstrate any clear benefit to breastfeeding on reducing obesity risk.)

7. "A bout of sexual activity burns 100 to 300 kcal for each participant"

(By their calculations the authors predict the average act of intercourse burns in the neighbourhood of 14 calories (sorry folks).)

The Presumptions 

These are subjects that as yet remain unproven one way or the other.

1. "Regularly eating breakfast is protective against obesity"

(Agree that it's not true for everyone. But perhaps important to note that the National Weight Loss Registry reports 78% of successful maintainers regularly eat breakfast. The flip side of that is that 22% don't. As I've blogged about (yesterday in fact), different strokes for different folks, though I'd argue (as would the Registry) that for most, breakfast may be important.)

2. "Early childhood is the period in which we learn exercise and eating habits that influence our weight throughout life"

3. "Eating more fruits and vegetables will result in weight loss, or less weight gain, regardless of whether any other changes to one's behavior or environment are made"

4. "Weight cycling is associated with increased mortality.."

5. "Snacking contributes to weight gain and obesity."

(Depends wholly on the snacks!)

6. "The built environment, in terms of sidewalk and park availability, influences obesity."

The Facts

These are the nine points the authors feel there's sufficient evidence to be true.

1. "Although genetic factors play a large role, heritability is not destiny"

2. "Diets (reduced energy intake) very effectively reduce weight, but trying to go on a diet or recommending that someone go on a diet generally does not work well in the long term."

3. "Regardless of body weight or weight loss, an increased level of exercise increases health."

4. "Physical activity or exercise in a sufficient dose aids in long term weight maintenance."

5. "Continuation of conditions that promote weight loss promotes maintenance of lower weight."

(Meaning whatever you do to lose it, if you want it to stay off, you need to keep doing it)

6. "For overweight children, programs that involve the parents and the home setting promote greater weight loss or maintenance."

7. "Provision of meals and use of meal-replacement products promote greater weight loss."

(The inclusion of this "fact" confused me consequent to point number 5! If you lose weight utilizing meal replacements and you stop using meal replacements, the weight lost as a consequence of their use may well return. What percentage of folks in meal replacement based programs are counselled or are prepared to live with meal replacements for life?)

8. "Some pharmaceutical agents can help patients achieve clinically meaningful weight loss and maintain the reduction as long as the agents continue to be used."

9. "In appropriate patients bariatric surgery results in long-term weight loss and reductions in the rate of incident diabetes and mortality."