The study of early pregnancy data on 26,561 mother-and-daughter pairs found that obesity rates had jumped four-fold between the two generations of women, from 3.1% among the mothers entering pregnancy in 1982-1988 to 12.3% among their daughters in 2000-2008.
"These findings add to the international evidence for a worsening intergenerational cycle of obesity," said José Derraik from Auckland University’s Liggins Institute, who was part of the research team.
The team, in collaboration with scientists from Uppsala University, analysed a rich body of data on Swedish women to better understand the long-term effects of early-life events and conditions occurring before, during and after pregnancy. Their findings were published in the journal Scientific Reports.
Obesity is a serious health issue for both mothers and their children in New Zealand, where almost one in three adults is obese, and a further 35% are classified as overweight, according to official figures. Among children aged 2-14, 33% are either overweight or obese, the 2015 New Zealand Health Survey found.
"Being obese increases a pregnant woman’s risk of developing pre-eclampsia, gestational diabetes, miscarriage and infant mortality," said Dr Derraik.
"Also, there is mounting evidence that obesity during pregnancy may affect children’s health not only in childhood, but also in adult life."
Other researchers have proposed an “intergenerational obesity cycle", where obese mothers provide too much nutrition to their babies during gestation, and the babies become adapted to store more fat in childhood and adulthood.
This striking rise in obesity rates could also be partly explained by the so-called "obesogenic environment", where the family diet and lifestyle could be fostering the development of obesity among daughters.
"This study underlines how vital it is to try to break the obesity cycle by doing what we can to prevent obesity early in life," said Dr Derraik.
Last year, New Zealand became one of the few members of the OCED club of wealthy nations to introduce a comprehensive plan to tackle childhood obesity which centres on healthy diets and exercise.
“Our plan focuses on children as that's where the evidence shows we can have the greatest influence,” said health minister Jonathan Coleman at the launch of the Childhood Obesity Plan. “By focusing on children we expect to also influence the whole family.”
Yet anti-obesity campaigners in New Zealand have strenuously argued that the plan doesn’t go far enough. Recently, more than 70 leading public health specialists signed an open letter to the Cabinet asking for obesity prevention measures to be strengthened, and called for a sugar tax to be implemented across the country.
One of the signatories, Boyd Swinburn of Auckland University, said current government policies were not enough to change the trend.
"New evidence has come to light, there's new international movement, particularly with the UK taking up sugary taxes, and there's a wave of public support for it," said Prof. Swinburn. “I really would like them to reassess their position.”
Public opinion has been seen to be swinging towards the policy, according to one survey, which found that around 66% of people favoured a tax on soft drinks, with only 29% against.
Yet support for a sugar tax is low within senior government and among industry groups. Prime Minister John Key said recently that there was no evidence that such a levy contributed either to public health or to Wellington coffers.
Katherine Rich, chief executive of the Food and Grocery Council, wrote in FoodNavigator-Asia a robust critique of the effectiveness of Mexico’s sugar tax in February, saying: “The punitive taxation of food and beverages to price goods beyond citizens’ incomes is unlikely to be a humane or effective solution.”