Children from lone-parent families, bottle-fed babies and kids who are sexually abused, are some of those who could be at most risk of becoming overweight or obese in adulthood.

A new study examining childhood factors for adult adiposity, published today in the New Zealand Medical Journal, has found that being born into a single-parent family, having parents with larger body size, and experiencing severe sexual abuse were the most significant predictors of those who would become overweight or obese as adults.

Other factors include having higher infant weight gain, limited or no breastfeeding and lower cognitive ability. Males had a higher mean BMI and bigger risk of becoming overweight or obese.

Researchers used data from the long-term Christchurch Health and Development Study (CHDS), which has followed 1,265 children born in Christchurch in 1977.

The present study examined participants’ backgrounds and assessed their body mass index (BMI) scores at birth, and at ages 30 and 35. It found that approximately one-third of people were overweight and one-fifth were obese by the time they were in their thirties.

The Ministry of Health estimates that 31.6 per cent of New Zealand adults are obese while rates are higher among Maori and Pasifika (47.1 per cent and 66.9 per cent respectively).

The government-led New Zealand Health Strategy aims to reduce obesity levels and the associated health and financial costs and its approaches include sport programmes, public education and better food labeling.

But this new University of Otago study suggests that obesity is caused by “a complex mix of childhood family background, biological endowment and individual factors beginning in pregnancy and early childhood”.

Factors such as gender, parental BMI and past exposure to childhood sexual abuse, cannot be changed. But it is still important to identify and understand them, the study’s researchers say, in order to help individuals and “develop more targeted and patient-specific interventions”.

Meanwhile factors such as little or no breastfeeding and weight gain in infancy, shown in a number of studies to be linked to adult obesity, are amenable to change, say the study’s authors.

“This suggests that the promotion of breastfeeding, the encouragement of longer periods of breastfeeding infants and monitoring the use of formula and the introduction of solids could play key roles in any strategy designed to reduce obesity.”

Other studies have found that if families are given help to make certain behavioural changes in a baby’s first 1,000 days this can be effective in reducing obesity. It may be possible for healthcare providers such as Plunket, Early Start and Family Start, to assist New Zealand families on this level, the study’s authors say.

Numerous international studies have identified that factors in childhood, such as growth, diet and activity, will determine a person’s weight in adulthood.

Less is known, however about the role of these factors in contributing to adult obesity in New Zealand specifically.

Study director John Horwood says that longitudinal studies are helpful in understanding the linkages between early risk and later outcomes. As well as the CHDS study and the world-famous ‘Dunedin Study’, other local longitudinal studies include the Pacific Islands Family Study (PIFS) and Growing up in New Zealand (GUINZ) and these cohorts are younger than the Dunedin and Chch cohorts).

However, we now know a lot about the risk factors for obesity in general, says Horwood.

“More important I think is the development effective interventions/ programmes that target known risk factors and obesogenic practices. I am not a public health expert in obesity prevention, but I think it’s fair to say that at the moment there is little evidence of efficacy for much of what we do by way of prevention/intervention.”

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