Mums with healthy habits 'less likely' to have obese children

"Mums with five healthy habits are less likely to have obese children," the Mail Online reports.

The headline is prompted by a new US study involving children aged 9 to 14. More than 24,000 children were studied, only 5% of whom were obese.

The study found that children were less likely to be obese if, while they were growing up, their mothers:

• had a healthy body mass index (BMI)
• did the recommended amount of weekly exercise
• were non-smokers
• drank alcohol in moderation

The fifth healthy habit was following a healthy diet. This wasn't found to have a significant link with child obesity on its own. But children with mothers who adopted all 5 healthy habits had a 75% reduced risk of obesity.

While this study can show links, it can't prove that the absence of these 5 maternal factors directly causes child obesity. However, it makes sense that if a child grows up with parents who have a healthy lifestyle, they are more likely to adopt a healthy lifestyle themselves.

Read more advice about adopting a healthy lifestyle as well as what options you have if you are worried that your child may be obese.

Where does the study come from?

The research was conducted by the School of Public Health in Boston, University of Guelph in Canada and other US institutions, and funded by the US National Institutes of Health. It was published in the peer-reviewed BMJ and is freely available to access online.

The reporting of the study in the Mail Online and The Times was accurate. In the same story, the Mail also reported on separate research looking at the geographical variability of child obesity in England. We have not analysed this other piece of research, so we are unable to comment on it.

What kind of research was this?

This was a prospective cohort study which aimed to look at the link between a healthy maternal lifestyle and the risk of obesity in the child.

Adult obesity is linked with many long-term health conditions like cardiovascular disease and diabetes, and certain cancers. Obese children are more likely to become obese adults, so there is much ongoing research into approaches that could prevent child obesity.

A large cohort study such as this is useful to look at whether maternal habits before and after the child's birth may be linked with risk of child obesity. However, no matter how plausible the links, with a cohort study it's not possible to prove direct cause and effect.

What did the researchers do?

The research made use of 2 cohort studies. The Nurses' Health Study II (NHSII) recruited 116,430 female nurses (aged 25-42 years) in 1989. They completed detailed lifestyle and health questionnaires at recruitment, and these were updated every 2 years. They completed food questionnaires every 4 years.

The dietary questionnaires asked women how often they consumed particular foods such as vegetables, fruit, nuts and whole grains with responses ranging from never to at least 6 times a day. The questionnaires also asked them about smoking and to estimate their average alcohol intake over the past year.

Similarly physical activity was assessed by questionnaire, and women self-reported their weight and height every 2 years.

The researchers aimed to score the women on 5 healthy factors:

• diet score in the top 40%, according to the Alternative Healthy Eating Index 2010 (this is a well-validated scoring system that assesses the nutritional quality of a person's diet)
• a healthy BMI (18.5 to 24.9)
• not smoking
• light to moderate alcohol intake (1.0 to 14.9 g/day – or no more than 2 units a day)
• physical activity of at least 150 minutes of moderate to vigorous intensity per week (as per current UK guidelines)

In 1996, any 9 to 14 year old children of the women in NHSII were invited to take part in the Growing Up Today Study (GUTS) – 16,882 children enrolled. In 2004, the study invited a further 10,918 children who were aged 9-14 years at the time. They also received assessments every 2 years.

The researchers looked for links between healthy lifestyle habits in the mothers and child obesity, adjusting for various socioeconomic and health factors for the mothers, as well as lifestyle factors for the children.

What were the basic results?

Of the 24,289 children studied, 5% (1,282) were obese.

Risk of child obesity was lower for mothers who followed 4 of the 5 healthy lifestyle factors:

• healthy BMI: 56% reduced risk (RR 0.44, 95% confidence interval (CI) 0.39 to 0.50
• recommended exercise: 21% reduced risk (RR 0.79, 95% CI 0.69 to 0.91)
• non-smoker: 31% reduced risk (RR 0.69, 95% CI 0.56 to 0.86)
• light to moderate alcohol: 12% reduced risk (RR 0.88, 95% CI 0.79 to 0.99)

While the risk for low alcohol intake only just reached statistical significance, the risk for the fifth factor of a healthy diet was not statistically significant (RR 0.97, 95% CI 0.83 to 1.12).

However, children with mothers who adhered to all 5 healthy habits had a 75% reduced risk of obesity (RR 0.25, 95% CI 0.14 to 0.47).

What did the researchers conclude?

The researchers conclude that their study "indicates that adherence to a healthy lifestyle in mothers during their offspring's childhood and adolescence is associated with a substantially reduced risk of obesity in the children."

They say that the findings "highlight the potential benefits of implementing family or parental based multifactorial interventions to curb the risk of childhood obesity."

Conclusions

This study makes use of a large quantity of observational data to look at the link between maternal lifestyle habits and child obesity. Although only a very small proportion of the children included in the study were obese, the sample size was still large enough to give fairly reliable statistical comparisons.

It seems entirely plausible that mothers with healthy lifestyle habits would be less likely to have obese children. It makes sense that if the mother/parents and other family members have a healthy lifestyle they are more likely to instil healthy habits in the child.

But the study does have some limitations.

As an observational study it can't prove direct cause and effect. It's not possible to say with certainty that the mother's lifestyle habits have directly reduced (or increased) the child's risk of obesity – however likely this seems.

All the findings were based on answers that were self-reported and these answers may not be entirely accurate.

This was a US study including only female nurses and their children. This particular group's lifestyle habits may not be representative of other population groups. For example, the child obesity rate in this sample was only 5%, much lower than estimates for the US population as a whole.

But overall the findings support current healthy lifestyle recommendations.