Higher BMI in the teenage years, even well within the range considered normal, is linked to early occurrence of diabetes and heart disease in young adulthood, and can predict them in a differential manner, according to a study that followed 37,000 Israeli army personnel for 17 years.

You can read how Dr Amir Tirosh, of the Endocrine Division at Brigham and Women’s Hospital in the US and the Sheba Tel- Hashomer Hospital’s Talpiot program in Israel, and Drs Iris Shai and Assaf Rudich, professors at the Ben-Gurion University of the Negev in Israel, and researchers from the Israel Defense Forces (IDF) Medical Corps and Tel Hashomer Hospital, conducted their study in the 7 April online issue of the New England Journal of Medicine.

Tirosh and colleagues found that elevated body mass index (BMI) in adolescence is linked to type 2 diabetes and heart disease in young adulthood, but in a different way in each case.

They found that risk for diabetes in early adulthood appears to be influenced mainly by recent BMI and weight gain, but in the case of risk for heart disease, the influence appears to come independently both from higher BMI in adolescence and recent BMI.

They suggest it could be that heart disease progresses gradually, probably as a result of gradually increasing atherosclerosis, narrowing of the arteries from plaque build-up, during adolescence and early adulthood.

What is surprising about this study is that the results were derived from BMI scores that were well within the range defined as normal.

Tirosh told the press that:

“Our results suggest that the obesity problem in children and teens is likely just the tip of an iceberg for increased risk for the occurrence of type 2 diabetes and heart disease in your 30s and 40s.”

He stressed this was an observational study, so it can’t prove cause and effect, but it highlights strong links that could suggest of cause and effect, and in this case it showed different types of link between BMI in adolescence and risk of developing diabetes and heart disease later in life.

For diabetes, the study suggests that growing to become a lean adult practically eliminates the risk of developing diabetes due to a higher BMI as a teenager.

But for heart disease, this was not the case. Even if he then becomes a lean adult, a teenage boy with a higher BMI has a higher risk of developing heart disease later in life compared to a teenager with a lower BMI. However, the risk will “still be lower than that of the heavier teen who became an obese adult”, said Tirosh.

Making an additional comment on the different relationship between adolescent BMI and risk of diabetes and heart disease, Shai said:

“It would seem that heart disease has a longer ‘memory’ for BMI than diabetes.”

For the study, Tirosh and colleagues followed 37,000 Israeli army career personnel, from the age of 17.

They recorded their BMI at the start of the study (baseline), and every few years over an average follow up period of 17 years.

Over the follow up, 1,173 of the participants developed type 2 diabetes and 327 were diagnosed with heart disease for the first time.

During this time, the average BMI of participants went up at a rate of 0.2 to 0.3 per year, a weight gain of about 30 lbs (13.6 kg) between the ages of 17 and 30.

After taking into account other risk factors for both diseases, such as age, fasting blood sugar, blood fats, blood pressure, family history, and smoking, the researchers discovered that BMI scores at age 17, even those considered to be well within the normal range, were able to predict the occurrence of both diseases.

Every increase in BMI of 1 unit was tied to about 10% higher risk of type 2 diabetes in early adulthood, and 12% increase in risk of coronary heart disease.

Previous studies have looked at associations between BMI in teen years and risk of these diseases in early adulthood, but they have not unequivocally confirmed a link.

“This study is significant because it demonstrates that the association exists within the currently-considered normal values for BMI, having distinct effect on two diseases occurring in early adulthood and in an age group that is frequently neglected,” said Rudich.

Higher risk of diabetes was tied to a BMI at age 17 of 23.4 kg/m2 or higher, while for heart disease, it was 20.9 kg/m2 and higher.

Note that these BMI values correspond to a male teenager of height 5’10” (1.78m) weighing 163 lbs (74 kg) or 146 lbs (66 kg) respectively.

Considering the clinical impact of this study, Shai said “history of a person’s BMI should be part of risk assessment.”

“We do have options, not necessarily pharmacological, to offer patients to decrease their risk for heart disease. Recent intervention trials showed that nutritional habits modification can not only halt the progression of atheorsclerosis, the underlying process of heart disease, but could also reverse it,” added Shai.

Tirosh noted that:

“For prevention of early occurrence of heart disease in adulthood it would seem that very early intervention to promote healthy life-style habits is warranted, even during childhood.”

Ben-Gurion University recently published a collection of studies that showed changing diet can not only stop, but also reverse, the progress of atherosclerosis, the underlying cause of heart disease.

“Adolescent BMI Trajectory and Risk of Diabetes versus Coronary Disease.”
Amir Tirosh, Iris Shai, Arnon Afek, Gal Dubnov-Raz, Nir Ayalon, Barak Gordon, Estela Derazne, Dorit Tzur, Ari Shamis, Shlomo Vinker, and Assaf Rudich.
N Engl J Med 2011; 364: 1315-1325.
Published online 7 April 2011; DOI: 10.1056/NEJMoa1006992

Additional sources: Brigham and Women’s Hospital, American Associates, Ben-Gurion University of the Negev (press releases, 6 Apr 2011).

Written by: Catharine Paddock, PhD