Mother and Daughter

Really? These Researchers Think BMI Is a Habit?

Harvard’s School of Public Health issued a press release last week that spawned a flood of headlines. Preventing childhood obesity is easy. They have scientific proof. All you need is a mom who follows five healthy habits. That’s right. Following those five habits will cut the risk by 75%. Habit #1: don’t weigh too much.

Not Having Obesity Prevents Obesity Best

In fact, if you read the research, you’ll find that a mom’s habit of having a BMI between 18.5 and 25 is the one linked to the biggest risk reduction in her children. It yielded a 56% lower relative risk of obesity. The other habits – not smoking, moderate alcohol, exercise, a healthy diet – didn’t even come close. For that matter, the relationship between a child’s risk of obesity and a mother’s healthy diet wasn’t even significant. But they threw it into the grouping anyway. Seemed like the thing to do.

Harvard Public Health wrapped up its press release by laying it on the line for mothers:

The findings of this study highlight the crucial role a mother’s lifestyle choices can have on their children’s health.

Choice, Correlation, Cause, and Effect

Ordinarily, this is where we might raise the question of causality. After all, these researchers say that they have a strong study, with long follow-up and a big sample. So they say it equipped them to “examine the impact of maternal factors.” Only in passing do they mention residual confounding and the limitations of observational studies.

But these folks have made a more serious error – assuming that a mother’s body weight is a choice and a habit. Ask clinicians who devote their careers to helping people who want to overcome obesity. They will tell you that this disease is not a simple matter of choice. Nor is it a habit. Genetic susceptibility and environmental triggers are the primary drivers.

Choices can have an influence, certainly. But behavioral scientists will tell you that they are not curative.

In the end, the assumption that body weight is simply a matter of choice represents a fatal flaw in this study. And through its PR blitz, Harvard’s School of Public Health is promoting misinformation about obesity and bias against people living with obesity.

Simply choosing not to have obesity won’t solve the problem for mothers and it won’t solve the problem for their children. False assumptions are no substitute for evidence-based strategies to improve public health. We expect more rigor than this from Harvard.

Click here for the study and here for Harvard’s press release. If you want a sample of the misleading headlines they spawned, click here. For further perspective from a mother, click here.

Mother and Daughter, photograph © CameliaTWU / flickr

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July 9, 2018

8 Responses to “Really? These Researchers Think BMI Is a Habit?”

  1. July 09, 2018 at 7:50 am, Chester Draws said:

    In the end obesity is caused by more calories in than out.

    No-one is obese when diets are limited. Countries where people don’t have enough to feed themselves are impo skinny even if the same genetic mix as obese prone countries (compare Mexico to Venezuela).

    That means anyone can be less than obese (which is not the same as skinny, because not everyone can be skinny).

    Pretending that people cannot lose weight is avoiding reality. It might be very hard, but it’s not impossible.

    • July 09, 2018 at 8:59 am, Ted said:

      Yes, indeed, Chester. Obesity prevalence goes down in times of war and famine. In other circumstances, curing obesity is not so simple as you seem to suggest. But perhaps I’m missing your point.

  2. July 09, 2018 at 1:31 pm, Patty said:

    Reading the Harvard press release, I noticed it starts with (in bold print no less) “Children and adolescents whose mothers follow five healthy habits — eating a healthy diet…. are 75% less likely to become obese when compared with children of mothers who did not follow any such habits” and ends with “To the surprise of the researchers, mothers’ dietary patterns were not associated with obesity in their children….” Hmmmmmmmm. Which one of these statements does not belong? Or am I missing some way to reconcile these two statements?

  3. July 10, 2018 at 5:58 am, johan said:

    @patty, there is a difference between a dietary pattern and healthy diet, one revers to how and when the mother eats and a healthy diet wich is healthy food. i can get the confusion but really that’s your best shot at debunking?

    a healthy diet/food is associated with a childs weight, think of having 3 portions of vegtables and not that meat only diet.
    a dietary pattern is how the mother eats, does she skip a breakfast or does she double down on it, these actions dont matter due the child being in most cases away from home for the day time.

    how hard is this….

    • July 10, 2018 at 7:53 am, Ted said:

      Thanks for commenting Johan. But I must admit, I’m having a hard time following your comment. Patty is right that the investigators did not find a correlation between a mothers’ dietary patterns and obesity in their offspring. So it’s odd that the investigators included healthy dietary patterns in the list of 5 maternal habits that are essential for preventing childhood obesity.

  4. July 10, 2018 at 1:34 pm, Richard said:

    Chester makes the mistake of assuming that because eating can affect body weight, it is the cause of obesity. Nikhil Dhurandhar (Past President of TOS) gives a wonderful analogy of obesity and breathing. We can consciously reduce our breathing rate, but as soon as we forget it goes back up. If we stop breathing we die and if we stop eating we die. But over-eating is not the cause of obesity, it is a symptom. The body’s physiological mechanisms are reset to cause obesity and are extremely hard to overcome by behavior.

  5. July 13, 2018 at 7:40 pm, Paul Ernsberger said:

    Thanks for taking on the Harvard combine, Ted! They seem to have forgotten that obesity is highly heritable.We see that every year on Twin’s Day in Twinsburg, Ohio. Identical twins not only weigh the same, but every aspect of their body shape and curves are the same. Thick upper arms, double chin, pot belly, muffin top, breast size are all identical in twins. Is that because of habit?

  6. July 18, 2018 at 8:19 am, Donna said:

    First of all Mr. Emsberger…I take offense to your implication that all identical twins are in the obese quadrant…my identical twin and myself have battled severe eating disorders…anorexia…our entire lives….All twins of ALL body types deserve more respect than the ‘side-show attraction’ element you appear to evoke here…Thank goodness for the ‘flip-side’ of commentary here…as evident in Richard’s astute commentary…He ‘gets it’…all. “..Over-eating is not the cause of obesity, it is a symptom”. This follows the science of Mr. Gary Taubes and Dr. Fung….Thank you for this call-out to evidence-based…up to date research.