Older sisters 40 per cent more likely to be obese than younger siblings


Click to follow
Indy Lifestyle Online

Firstborn sisters have a higher chance of being obese than their second-born female sibling, new research has found.

The research, which examined the weight of more than 13,000 sister pairs, found birth order could play an important role in determining weight.

The study, from the University of Auckland and Sweden's Uppsala University, is the largest of its kind and was published in the Journal of Epidemiology & Community Health.

Using data from 1991 to 2009 found on the Swedish Birth Register, the researchers measured the weight and height of the sister pairs from their mother's first antenatal visit. Twin sisters were not included in the study.

The experts also noted information about health, lifestyle and family history.

The results of the study found the firstborn sister had a 2.4 per cent higher body mass index (BMI), at 0.57kg, than their second-born sister.

The firstborn also had a 29 per cent increased chance of being overweight and a 40 per cent increased chance of being obese.

The study backed up similar patterns found regarding male birth order. Although the reason behind the difference between siblings was not clear, experts suggested it could be down to shrinking family sizes.

They said: “Our study corroborates other large studies on men, as we showed that firstborn women have greater BMI and are more likely to be overweight or obese than their second born sisters.”



Over the 18-year period, the experts found BMI increased by 0.11kg each year.

“The steady reduction in family size may be a contributing factor to the observed increase in adult BMI worldwide, not only among men, but also among women," it said.

In later life, firstborn siblings could be more at risk of health problems such as diabetes and high blood pressure than their siblings, according to the researchers.

Additional reporting by PA