Weighing in on Body Mass Index


Your 17-year-old son is healthy enough. He could stand to exercise more — video games take up more of his time than you'd like — and he enjoys the usual teen-age treats — burgers, fries, ice cream.

Yet his weight is normal, and he has a Body Mass Index of 23, within the normal range, which is thought to be less than 25.

No need to worry, right?

Think again. A study led by Dr. Amir Tirosh of Sheba Tel-Hashomer's Talpiot program, Brigham and Women's Hospital and Harvard Medical School, and Ben-Gurion University professors Iris Shai and Assaf Rudich — along with researchers from the Israeli Defense Forces Medical Corps and Tel Hashomer — shows a need to re-adjust the normal figure downward.

In this study, "Adolescent BMI Trajectory and Risk of Diabetes Versus Coronary Disease," published in a recent issue of the New England Journal of Medicine, the researchers found that what had previously been considered a normal BMI at age 17 could still increase diabetes and heart attack risk between the ages of 30 and 45.

Further, while losing weight reduced the risk of diabetes, it did not reduce the risk of heart disease.

The subjects under study– 37,000 men in the IDF — were followed from the age of 17 to 34. Their BMI was recorded at baseline and again every several years.

By age 30, participants had gained an average of about 30 pounds. During that period, 1,173 new cases of diabetes and 327 new cases of heart disease were diagnosed.

Risk Remains

While the risk of diabetes could be reduced with weight loss in adulthood, the risk of heart disease remained, even if the subject had lost weight.

For example, if a 17-year-old has a BMI of 23, his risk of diabetes is higher; however, he can reduce the risk by losing weight after this measurement is taken.

However, even if he does so, he remains equally at risk for heart disease. Of course, learning healthy lifestyle choices at any age makes sense, especially since diabetes can lead to a host of other complications.

So if that 17-year-old trades fries and cheeseburgers for fish and salads, and sets aside the video games in favor of some outdoor exercise, he will see the benefits.

As BMI levels increase, even within the normal range, risk factors will rise, says Shai. Hence the need to monitor lifestyle choices early.

As Shai elaborates, "We believe a healthy lifestyle is the key point to all future morbidity, and indeed, increased BMI levels in our study were associated with worsened levels of blood biomarkers, clinical parameters and physical activity,

"Thus, for those with relatively higher BMI within the normal range, we would like to suggest improving their lifestyle."

The study also shows how vital it is to reinforce healthy eating habits in children as early as possible.

Shai says she believes that schools can contribute a great deal to this effort, through the food they make available in menus offered in school cafeterias.

But, she adds, "There is still much more to do" to realize this goal.


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