Adolescent Obesity Tied to Parents’ BMI at the Same Age

Children born to parents who had obesity at age 17 had a much higher probability of having obesity at the same age, an Israeli cohort study suggested.

Among nearly 450,000 offspring, 76.6% of 17-year-olds whose parents had obesity at age 17 also had obesity or overweight themselves, according to Gabriel Chodick, PhD, of Tel Aviv University in Israel, and colleagues.

Only 15.4% of youth had overweight or obesity if both parents had a healthy BMI at age 17, the group reported in JAMA Network Open. When both parents were severely underweight, just 3.3% of offspring had overweight or obesity.

There was a correlation of 0.386 between midparental and offspring BMI, indicating a moderate heritability association, Chodick and co-authors wrote. Midparental BMI was an average of the mothers’ and fathers’ BMI cohort-specific and sex-specific BMI percentile.

Compared with healthy-weight parents, the odds of obesity at age 17 significantly increased if either parent had obesity, but were highest if both parents had it:

• Maternal obesity: OR 4.96 (95% CI 4.63-5.32)
• Paternal obesity: OR 4.48 (95% CI 4.26-4.72)
• Both parents with obesity: OR 6.44 (95% CI 6.22-6.67)

Offspring also had a significantly higher probability of obesity if either parent or both parents were overweight at age 17, ranging from 2.89-times to 3.11-times higher odds.

“Genetics plays a major role in child’s and adolescent’s obesity,” Chodick told MedPage Today. Despite this, the earlier a child can be identified as “at risk,” the easier it will be to adopt healthy lifestyle habits, he pointed out.

“Previous studies examined parents and children at the time — not the same age — so it was difficult to distinguish between the genetic effect and the effects of their shared household lifestyle,” Chodick added. “In our study, parents were measured at age 17, way before the household was established.”

There were stronger associations between parental obesity in female offspring than male offspring. There also was a stronger correlation in BMI percentile between mothers and daughters compared with mothers and sons. Compared with paternal obesity, maternal obesity was linked with higher odds of obesity in female offspring.

“This finding not only underscores the complexity of genetic and environmental interactions but also may suggest potential sex-specific influences on the heritability of BMI,” the researchers pointed out.

The correlations largely remained the same across the calendar year of offspring BMI measurement, health status, and number of siblings.

The analysis was based on 447,883 offspring and their parents, yielding a total cohort of 1,343,649 individuals. The study sample included Israeli military enrollees who underwent population-wide mandatory medical screening prior to compulsory service. Data were collected from 1986 to 2018. About half of the offspring (47.5%) were born in Israel, 21.5% were born in Europe or the U.S., 15.9% in Asia, 13% in Africa, and 2% in the former Soviet Union.

Among the offspring, 52.5% were male, median birth year was 1993, average BMI was 22.22, and average weight was 63.46 kg. Median birth year of the parents was 1962, average BMI was 21.36, and average weight was 60.49 kg.

One limitation to the study was a lack of other weight-related clinical data like waist circumference, which isn’t measured among recruits in the Israel Defense Force. Chodick’s group noted that “it was previously shown that both maternal and paternal waist circumference is associated with a higher waist circumference of their young adult offspring, with a substantially greater regression coefficient compared with the correlation in BMI.”

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