More than 18 percent of elementary-school-age students in the United States are obese, and no one really knows why. The causes are numerous and tangled. But consuming too much sugar is widely accepted as an important factor. In 2015, the World Health Organization issued a recommendation: Everyone, regardless of age, should restrict his or her sugar intake to less than 10 percent of all calories consumed daily. For young children, that would mean no more than about 45 grams of sugar a day. Of course, few young children are responsible for their own diets or can be expected to capably monitor their sugar consumption. That oversight usually falls to a parent. And a recent study published in the International Journal of Obesity suggests that most of us, alas, are not adept at estimating how much sugar is in some common foodstuffs.
For the study, researchers with the Max Planck Institute for Human Development in Berlin visited 305 German families that included at least one child between the ages of 6 and 12. Each child’s body mass index was calculated, and the parent who planned and provided most family meals – usually, but not always, the mother – completed a simple computer quiz. The parents were asked to estimate the sugar content in various foods and beverages; these included orange juice, yogurt, pizza and ketchup, all of which are common in the diets of young children. To help the parents visualize sugar volumes, they were told to think in terms of sugar cubes and that each cube contains roughly 3 grams of sugar.
About three-quarters of the parents underestimated the total amount of sugar in the foods – in some cases radically, with the biggest divergences happening around foods commonly seen as “healthful.” More than 90 percent of the study participants underestimated the sugar in yogurt, for instance, by an average of seven cubes, or about 60 percent of the total sugar in each serving. More concerning, these misjudgments turned out to be related to children’s body weights: Those with the highest B.M.I.s tended to have parents with the largest underestimates.
Because this was a correlational study, the results do not prove that children will gain weight if their parents are wrong about how much sugar is in pizza, say, or ketchup. (The parents happened to overestimate the sugar content in ketchup.) Still, the findings offer reason for caution. “We were surprised by the degree of sugar underestimation for some of the products,” says Mattea Dallacker, a postdoctoral fellow at the Max Planck Institute who conducted the study with Ralph Hertwig and Jutta Mata. Dallacker and her colleagues suspect that a “health halo” hovers over things like fruit juice and yogurt, leading parents to misjudge the sugar in them. Dallacker says they would like to see food labels include a “traffic-light system”: a red dot for high sugar content, green for minimal sugar content. Until that happens, she suggests that parents sweeten foods themselves. “Mix natural yogurt with fruit,” Dallacker says. “Parents who do this would hardly feel compelled to add 11 sugar cubes.”