Otago University study reveals childhood factors which contribute to adult obesity

A new study has revealed some of the factors which can lead to obesity. Photo / File

Being a male, born into a single-parent family, having parents with larger body sizes, higher early-infant growth, limited or no breastfeeding, lower levels of cognitive ability and exposure to severe sexual abuse are all factors which can contribute to adults being overweight.

A study, carried out by Otago University and published in the New Zealand Medical Journal today, has pinpointed some of the factors in children which could help predict issues with being overweight or obese as an adult.

The research is the first glimpse into the reasons behind New Zealand's obesity epidemic but was in line with the findings of similar studies in other parts of the world.

The study of 980 children born in Christchurch in 1977 found about half were overweight or obese by the time they hit 30, and that figure hit almost 60 per cent by the time they were 35.

While men and women were equally likely to be obese, the study found men were more likely to be overweight - 63 per cent of men in the study were overweight compared to 45 per cent of women.

The study authors concluded the most important predictors of people being overweight or obese were being born into a single-parent family, having parents with larger body sizes and experiencing severe sexual abuse.

The percentage of those in the study with an unhealthy weight steadily increased with both the weight of the mother and father, while 73 per cent of those born into a single-parent family were overweight or obese compared to 53 per cent of those born into a two-parent family.

Of those who reported being subjected to severe sexual abuse under the age of 16, 70 per cent weighed too much compared to 53 per cent of those who did not.

Other factors also played a part, the study found.

A higher body mass index was also associated with lower maternal education and living standards, greater infant weight gain, maternal smoking during pregnancy, the child not being breastfed, the introduction of solid foods at age two months or younger.

Those who were overweight or obese were more likely to be Maori or Pacific Islanders, to have had attention or conduct problems in childhood, to have sleep problems and to be of lower cognitive ability, according to the research.

Overall, the net impact of the risk factors on the average body mass index ranged from one to three Body Mass Index units.

Director of the Christchurch Health and Development Study and one of the researchers for this project Professor John Horwood said the findings were in line with international evidence and reflected a "complex mix of factors" associated with the problem.

"Individually, the identified risk factors have a relatively modest impact on adult weight, but jointly they can add up to something that is substantial," he said.

"So, if you have three or more risk factors there is likely to be an associated increased risk of obesity."

The researchers concluded that most of the risk factors identified in the study could not be altered by obesity-prevention programmes.

Rather, they suggested, the childhood factors associated with obesity later in life could help programmes target high-risk families and individuals.

With New Zealand ranked the third most obese nation, any research producing methods to tackle the epidemic were welcome," he said.

"We're clearly at the higher end of the obesity game internationally so anything that might inform our way forward is particularly useful."

In 2016/17, 32 per cent of New Zealand's adults were obese and a further 34 per cent were overweight while one in eight children aged 2-14 years were obese and another 21 per cent were overweight.

The study participants would continue to be monitored throughout their lives and Horwood expected the coming years would provide valuable information about the effects of obesity.