Te Puke Family Budgeting co-ordinator Angela Saunders said busy, modern lifestyles made cheap, easy meals such as takeaway pizza more convenient for people.
"When you've got three kids screaming at you because they're hungry, it can be quite stressful," she said.
People seemed less inclined to cook at home as a result, Ms Saunders said.
However, she urged people not to be drawn in by sugary foods, which were often cheaper than healthy produce.
"It's hideous to have fizzy, high-sugar drinks cheaper than bottles of water."
Monthly figures show soft drinks, coffee and fruit juice prices fell 2.6 per cent, 5.6 per cent and 6.1 per cent respectively in December.
Ms Saunders suggested the Government consider shifting funds from Work and Income family tax credits towards providing meals in schools.
This would ensure children from struggling families were fed nutritious meals at school, she said.
A study led by the University of Otago published this week in the British Medical Journal found the risk of being obese and overweight in children increased as more sugary drinks were consumed.
Lead study authors Dr Lisa Te Morenga and Professor Jim Mann called for a stronger focus on nutritional information targeting sugar intake.
"It seems easier to overeat if your diet includes lots of sugary foods and drinks. When you overeat, you gain weight," Dr Te Morenga said.
Heart Foundation national nutrition adviser Delvina Gorton said: "Ideally we'd like to see the prices of fruit and veges going down to encourage people to eat more and the price of sugary drinks, which we want people to have less of, going up."
Ms Gorton advised people to look for seasonal specials on fruit and vegetables.
For example, a carrot costs about 30c at the moment, she said.
Statistics NZ price manager Chris Pike said the monthly decline in non-alcoholic beverage prices reflected lower overall food prices last month.
Prices were down 0.2 per cent in December and 1 per cent year-on-year.
