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Teens whose body-mass index is in the upper range of “normal” — not overweight or obese — could still be at an increased risk of dying from cardiovascular diseases as they reach middle age, according to a huge new study of Israeli adolescents.

Why it matters:

Both being underweight and overweight are risk factors for cardiovascular diseases. But this study hints that even BMIs “which were considered in the normal range are actually related to cardiovascular diseases and even death,” said study author Dr. Gal Yaniv, a radiology resident at Tel Hashomer Hospital in Tel Aviv, Israel.

The nitty-gritty:

The researchers used data collected on 2.3 million Israelis during the medical exams that preceded their obligatory military service between 1967 and 2010. The medical records from those physicals allowed the researchers to calculate participants’ BMIs at age 17, and then to correlate that information with causes of death as recorded by the country’s Bureau of Statistics.


Until 1981, only military-related deaths were tracked, but more complete statistics were kept for the next 29 years.

Those who were obese or overweight were most likely to die of cardiovascular causes. But the researchers were also surprised to find that those at the higher end of normal weights were also at an increased risk. The results were published in the New England Journal of Medicine. “Maybe the ‘normal’ BMI range should be reconsidered,” said Yaniv.


But keep in mind:

The Centers for Disease Control and Prevention isn’t about to change its classification of a normal BMI based on one study.

“There is no magic threshold at which all of a sudden people are at higher risk,” said Paul Franks, a nutritionist at the Harvard T. H. Chan School of Public Health, who was not involved in the study.

He pointed out that it’s hard to know if this group of Jewish Israelis is representative. The sample is big, but it also only includes those who have served in the army of a country that has been in a near-constant state of conflict, which could increase stress levels.

It’s also hard to make clinical decisions based on this kind of association study, given that the trajectory of someone’s BMI may well be set in early childhood, or even in utero. “The important clinical question that remains unanswered: if you intervene with adolescents to lower BMI, will that decrease risk?” he said.

The bottom line:

BMI during adolescence may be associated with your risk of dying from cardiovascular diseases — but more studies are needed to know if changing a teen’s weight will, in turn, change that risk.