Food cop ... Karen Doughty, with Ella and Samuel, tries to keep treat foods for special occasions.

Food cop ... Karen Doughty, with Ella and Samuel, tries to keep treat foods for special occasions. Photo: Jacky Ghossein

KAREN DOUGHTY finds it exhausting playing the ''food nazi''.

It's frustrating because children see these ads and think that the food is good for them but often that's not the case. 

But her two children, Ella, 9, and Samuel, 6, know that pester power is an effective strategy.

''I hate having to be the food nazi,'' Mrs Doughty, a member of The Parents' Jury, said.

''Having to be the food cop all the time is just exhausting.''

The Balgowlah mother said marketing of food can often blur the lines between everyday food and treat food.

''It's frustrating because children see these ads and think that the food is good for them but often that's not the case,'' she said. ''It's hard to explain how advertising works to young children.''

Pester power is one of the biggest battles parents face in keeping their children healthy, according to The Parents' Jury, a network of parents and health professionals committed to improving children's wellbeing.

''The food industry spends millions each year advertising in a number of ways which appeal to children,'' campaign manager Corrina Langelaan said. ''It's not just television any more. [Children] can be targeted walking down the street, through social media, branding and sporting events, even fund-raising in schools.''

The National Preventative Health Taskforce has recommended the phasing out of advertising energy-dense nutrient-poor foods before 9pm on free-to-air and pay TV.

Junk food advertising is voluntarily restricted during children's programs which air in the late afternoon but, research from the Australian Media and Communications Authority shows that about five times more children watch television after 6pm.

The nutrition program manager at the Cancer Council NSW, Clare Hughes, believes industry self-regulation of food and beverage advertising is not working.

''There is strong evidence that the voluntary code has had very little impact on what children are seeing on TV,'' she said. ''That's simply because [it is] not applied to the programs that kids are actually watching.''

The Cancer Council NSW launched a website last week rating popular family programs by the number of junk food commercials screened when they are on. The worst offenders were AFL coverage, The X-Factor, Dancing With the Stars, The Simpsons, Junior MasterChef, Sunrise and Saturday family movies screened on Nine and Ten.

Gerri Minshall, a clinical psychologist at the weight management unit of Sydney's Children's Hospital at Westmead, which is supporting The Sun-Herald's Healthy Habits campaign, recommends warning children about not buying junk food in the first place. If they throw tantrums, she advises that parents try to remove them from the situation and to reward them when they do not pester.

Mrs Doughty has developed techniques to handle pester power.

''We take the line that there are everyday foods and there are treat foods and the treat foods are just for sometimes,'' she said.

''I let the bar drop when we're on holidays, for example. That also means I don't have to be the bad guy who says no all the time.''