Thursday, August 12, 2010

harmful assumptions abound; calorie counts and BMI

Recently a study found that most Americans don't know how many calories they are "supposed" to eat in a day.

"... some simple calorie know-how would go a long way toward helping people lose or maintain their weight. " Really?

It went on in the typical manner of "tsk, tsk, if the people only knew how many calories they needed to eat, we could finally tackle the obesity epidemic."

This is an example of a cultural belief that goes largely unquestioned that more information, more cognitive control, more knowledge of calories/fat grams would help. I would posit that it is as likely to be harmful. Are there any studies that show that when people know how much, or what kinds of food they "should" eat that they are more likely to do it? I would guess that many life-long dieters and disordered eaters know better than anyone how many calories they should eat, the exact calorie counts of foods etc and still struggle mightily with eating and weight. If only knowing how much to eat would solve the problem, then Weight Watchers Point System would work, when in fact they have a similar failure rate of most diets around 90-95%...

Another example of unquestioned assumptions is the general belief that if only parents KNEW their child's BMI, had that note or diagnosis labeling their child as 'obese' or 'overweight' that we would finally get this childhood obesity thing under control! It is this thinking that is pushing ever more aggressive screening at doctor's offices and schools. Intuitively it seems to make sense, but several studies suggest that labeling children with BMI leads to MORE dieting, MORE disordered eating, LESS physical activity and MORE weight gain for children. Handing that parent the red-slip is more likely to do harm than help the child.

I would just like to see a little intellectual effort in our public health arena and health reporting.

Can you think of other "assumptions" about eating, health or weight that go unquestioned but are highly questionable?


  1. Katja, welcome back! I hope you had a great vacation.

    My biggest complaint/worry about telling people how to lose weight is that theories keep changing. When we were told to not eat fat, sugar, often times A LOT of sugar was used to make fat free food taste good. Then it was no carbs, but after a decade of replacing fat with sugar, it's hard, really hard to give up the carbs.

    Even non-food advice keeps changing. The first time I ever gained a lot of weight due to a medication, I didn't even know it until I had already gained a significant amount of weight because I was following the advice of not weighing. Even doctors weren't regularly weighing me then. At the time, it felt like good advice since my parents had passed their obsession with my weight on to me and there had been times in my life when I weighed several times a day, but that advice did not work out for me.

    Advice about exercise has changed over time too, not only how long we should exercise, but how, it used to be that weight lifting was not encouraged, only aerobic activity, and now it's different.

    Any advice to parents will be open to interpretation and most importantly doesn't take into account what the kid needs or wants, emotionally and physically. I have lived the nightmare of parents trying to control the weight and eating habits of their child, and I wouldn't wish that on anyone.

  2. Every time I think of this, I come back to the basic assumptions about relevance and control. As in, "it is important how much you weigh", "and you can control it".

    And I think "weight" is used as a stand-in here for things that have only a marginal correlation to weight, but are a lot more complicated than a single number (or ratio): Health, self-determination, feeling compentent, a desire for love, or youth, or respect...

    To start with health, which can reasonably be measured: There is a busload of things more important to it than your weight. But weight is so nice and simple that it gets used as a stand-in for things more complex and/or less perceived as controllable.

    Like the drunk who is searching for his keys under the streetlight, because the alley where he lost them is too dark to find them there, we are fixated on the dubious cone of light thrown by a single number as if it would help us find what we are looking for.

  3. Hear, hear! What a refreshing point of view, especially coming from an MD. I see you're affiliated with the Ellyn Satter Institute--that explains a lot! (I"ma big fan and a friend of Ellyn's.)

    Thank you for this blog, and for your thoughtful perspective on these issues.

    --Harriet Brown

  4. I agree with you. Focusing on the numbers is merely a game--and in the end you will have winners and losers. Winners meaning folks who will use the information productively not obsessively; and losers who will ultimately run into more problems with weight and eating. A little bit of knowledge can be helpful and an over-obsession with numbers/nutrition, etc can be destructive. We can't ignore the problem, however, we need to effort prevention to a greater degree. Minimizing the focus on numbers and instead helping people focus on behaviors that produce a healthy person is the way to go. If you focus on behaviors, the numbers will follow naturally.