Tuesday, October 23, 2007

Maybe You Didn't Earn that Latte

Yesterday was another fine day at the Obesity Society conference with so many fascinating abstracts presented.

I'm going to fill you folks in on the work of a very dynamic speaker and clearly talented researcher, Dr. Tim Church.

Tim's gang wanted to explore whether or not exercise led patients to "overcompensate" with food - meaning they wanted to see whether or not we rewarded our exercise with more food than we earned.

It was truly an elegant experiment.

Firstly individuals had to sign an informed consent paper that explicitly stated that the study being conducted was not in fact a weight loss study, but rather a study on the effects of exercise on blood pressure and fitness. The authors simply didn't want people influenced by the thought that they were involved in a weight loss study.

For 6 months, 464 post-menopausal women were randomly assigned to a control group of no supervised exercise, 72 minutes, 136 minutes or 192 minutes per week of exercise. The exercise was kept at moderate intensity and it involved using a treadmill or an exercise bike and all of the exercise was supervised exercise so that they would not have to rely on unreliable self-reported amounts.

Retention for the study was great with 94%, 87% and 93% retention in the treatment arms.

Fitness showed a non-surprising and beautiful dose dependent response with more exercise leading to greater improvement.

Weight however was a different story.

The 72mins per week group lost on average 1.3kg over the 6 months.

The 136mins per week group lost on average 1.9kg over the 6 months.

And the 192mins group, did they lose 2.5kg?

Nope, they only lost 1.3kg.

It gets more interesting.

When they looked at the actual data points what they saw was that weight loss progressed well during the first 10 weeks of the 192mins per week group, but that was during their so-called, "ramping up" period whereby they couldn't have simply started these folks at 192mins per week, so they were ramping them up to 192mins. Almost as soon as they did reach their 192mins mark, weight loss slowed down to a crawl.

Now remember, I mentioned this was an elegant study. The authors, anticipating the skeptics, wanted to eliminate an obvious confounding question. Did the folks who were exercising the most simply do less the rest of the week because they were either too tired from exercise, or felt that they didn't need to worry about day-to-day activity because they were good at getting their pump on? Nope. Tim and his buddies had subjects wear pedometers daily to ensure that the exercise didn't have an effect on non-exercise activity and steps across the board were in fact the same.

So what can we conclude?

It's got to be an intake thing again. Whether the increased exercise led to an actual increase in hunger or whether it simply made folks falsely confident of what they were allowed to eat (the calories they earned through exercise) isn't clear, but what is clear - more exercise led to disproportionate increases in intake.

Maybe you didn't earn that extra Latte.

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2 comments:

  1. Anonymous5:59 pm

    Coincidentally on the subject of lattes, today I (on an impulse because my mouth felt yucky and I was having a stressful day) treated myself to a Chai Latte from Second Cup. Afterward I checked the calories on the website.

    Holy moley! 380 calories for a 16 oz skim milk chai latte!

    (I was expecting around 200, which is what the equivalent Starbucks offering is. Still more than a can of coke, but not diet-busting if you adjust for it.)

    What was more horrifying was the 3g of trans fat (6g total, only 1g unsaturated). Yikes.

    I'm really regretting not going to Starbucks instead. Or making my own.

    Overestimating with reward eating is one of the reasons I have to count. Leaving it up to intuition is always a mistake.

    P.s., I enjoy your blog quite a lot.

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  2. Lindsay2:08 am

    This is a great study... I'm interested in whether the research team had the subjects keep a food journal or track calories consumed.

    Also, how many of the subjects were overweight or very active to being with?

    Thanks!

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