Monday, August 16, 2010

Healthy Dads, Healthy Kids, and Unhealthy Peer Review.

Last week Colby Vorland tweeted a link to a new study that looked at the impact of a lifestyle modification program geared at overweight fathers and their children.

The study set out to randomly investigate something called the Healthy Dads, Healthy Kids Program - a 3 month program that delivers 10 hours of behavioural change counseling to overweight dads and their kids (where the kids showed up for 4 of those). The study looked at dads' and kids' weights at the end of the program and 3 months later, and for a control group they used dads and kids on the program's waiting list.

The 6 month outcomes were quite predictable.

Healthy dads lost significantly more weight (15lbs vs zip), and had statistically significant improvements in their waist circumferences, blood pressures and physical activity compared to controls. Importantly, they did not report any difference in their dietary intakes.

Healthy kids showed an increase in physical activity and their mothers reported a dramatic decrease in the kids' caloric intake, reporting them eating on average 20 calories less per kilogram. Given the reported average weight of the children was 33kg, that'd be a decrease of 660 calories per kid per day - yet there was no change in weight in the children.

So is this a slam dunk? Should we be rolling out this program across the globe?

Not yet.

You see there's an enormous flaw in the study, and it's a flaw that the folks who designed the study absolutely knew beforehand. Simply put, if you graph weight loss over time for virtually any weight management program, the losing phase lasts roughly 6 months which is then almost invariably followed by the regaining phase.

Put another way, it's not particularly exciting to see a program effectively leading to weight loss at 6 months given that pretty much any intervention can do so. In fact I'd go so far as to say that publishing 6 month results of a weight loss program is a knowingly misleading thing to do and something that should be considered heavily by peer reviewers when evaluating such papers.

Furthermore the study illustrates the difficulty of food frequency questionnaires in accurately tracking intake because here we've got a pile of kids who are apparently not governed by the laws of thermodynamics in that they're supposedly exercising significantly more and purportedly eating dramatically less and yet they aren't losing any weight.

Dads wise - the study's fairly predictable too. Having treated over one thousand men in my program I can tell you, without frequent and explicit guidance to the contrary, men tend to hit the gym hard and fast and ignore food. While that may work in the short run, I've never seen it work in the long run in the absence of dietary change.

So before you enroll in one of these programs I'd suggest you wait for the 18 month data.

Of course the cynic in me says that data's never going to get published, not because of the International Journal of Obesity's negative publication bias, but rather because it's not data the researchers will likely want to brag about.

Morgan, P., Lubans, D., Callister, R., Okely, A., Burrows, T., Fletcher, R., & Collins, C. (2010). The ‘Healthy Dads, Healthy Kids’ randomized controlled trial: efficacy of a healthy lifestyle program for overweight fathers and their children International Journal of Obesity DOI: 10.1038/ijo.2010.151