Empowering kids to eat smaller portions
Cut through all the blather about low carb, high fat, paleo, Mediterranean, and you're left with a basic physical fact: Calories in must equal calories out. If more are consumed then expended, the difference is stored as fat.
Portions have increased dramatically over the last half-century - restaurant meals quadrupled in size - and nearly a third of American children are now overweight or obese.
So it was a little surprising to discover the other day that most of the world's experts in portion size, along with some assistants and graduate students, could fit into a small meeting room at the Four Seasons (and show admirable restraint at the mouthwatering buffet).
The focus of the conference would be how to develop healthy portion-size behavior in children. First, however, everyone around the U-shaped table said a few words.
Marion Hetherington, a biopsychologist at the University of Leeds, who was wearing a fruit-and-vegetable pin and a necklace with cherries and a pretzel, mentioned a paper she had read that found chimpanzees misjudge portion sizes exactly the same way humans do.
And Leann L. Birch, a nutrition professor at the University of Georgia, spoke for everyone: "I'm interested in why children eat the way they do."
The answer, it became clear through several presentations during the day, is parents.
Variants of the FTO gene influence when children feel full. The CCK gene is involved with meal size. LEP (leptin) is linked to extreme snacking behavior. MAOA and COMT affect high-sugar and high-fat intake in children.
In fact, most eating behavior is inherited - but not necessarily through genetics.
A paper published online in January in the American Journal of Clinical Nutrition described researchers' detailed observations of 145 low-income parents and their preschoolers as they ate normal dinners together at home. Everything was photographed and cataloged; each bit of leftover was weighed to the nearest 10th of a gram.
The key finding: The amount of food parents served to their children accounted for 73 percent of the variation in how many calories the children consumed.
"I find that to be extraordinary," said first author Susan L. Johnson, a professor of pediatrics at the University of Colorado School of Medicine. "Because if you talk about what parents tell you about what children eat, they'll say, 'They only eat sweet things,' or, 'It's hard to get them to eat vegetables.' "
The median amount parents served to kids was actually more than the parents consumed. Yet children, Johnson speculated, may interpret the serving - often followed at some point with the admonition to "clean your plate" - as an expectation of how much they should eat.
Other studies have shown that when children are allowed to serve themselves, they typically choose and eat less.
Snacking, too, is largely controlled by parents, with a big assist from advertising, single-serving sizes, and availability from convenience stores and even auto-repair shops.
People who grew up in the 1960s and '70s don't remember many snacks. Now, "kids are snacking on average six or seven times a day," said Kirsten Davison, an associate professor of nutrition at the Harvard School of Public Health.
Her research into parental approaches to snacking isn't finding much attention paid to amounts. It's more often about control or reward, she said, or simply love: " 'I give my kids food because I love them. I want them to love me.' "
One of the conundrums of the field involves self-regulation. Children younger than 2 generally eat when they're hungry and stop when they're full. Starting around age 3 or 4, just as they are gaining more control over their environment, kids seem to lose control over their appetite and let external cues shape how they eat. The habit continues into adulthood.
Hence, the focus on parents - both educating them and convincing them of the power of trickery.
The Delboeuf illusion is the reason chimps misjudged their portion sizes, choosing smaller portions of foods they always want more of.
Basically, as numerous studies have shown, a portion will appear smaller when served on a big plate than on a small one. So large plates cause people to take and eat more. (And plate sizes have grown about 25 percent over the last century.) Short, wide glasses have the same effect; better to pour drinks into tall, narrow ones.
Stanford University pediatrics professor Thomas N. Robinson is using the illusion in one of the few research attempts to trigger weight loss in children by changing their environment.
His team packed up and replaced families' dishware - plate surface areas were reduced 20 percent, glasses 30 percent, mugs 40 percent, and bowls 50 percent - and is making numerous other changes over seven months: Kids must sit to eat, not move around the kitchen; a water pitcher is placed on the table; foods are divided into "red-light" (must be served by parents and stored out of sight after meals) and "green-light" (kids can take, always left out); TV is blocked at mealtime.
Findings are not complete, but Robinson said they were encouraging.
Jennifer Orlet Fisher, an associate professor of public health and interim director of Temple University's Center for Obesity Research and Education, is using eight-inch plates imprinted with photos and descriptions - "1/2 cup mac & cheese"; "6-inch soft tortilla, 1 oz pork, 1 tbsp salsa" - of actual-size children's portions as part of research into how to educate parents in the federal food-stamp program. It is one of the first attempts to convert portion-control strategies developed in the lab into a real-world obesity-prevention program for children.
The academic study of portion sizes is less than 25 years old. Barbara Rolls, a nutrition professor at Pennsylvania State University who mentored many at the conference, is probably the singular leader in the field, especially for adult portions. Fisher and Birch, who recently moved from Penn State to Georgia, have done most of the work in children.
Much is still unknown: Which kids are most likely to overeat? How does portion size interact with energy density (vegetables vs. meat)? Is it better to teach parents about appropriate portion sizes or children about how to know when to stop? How do you get around the biologically programmed perception that bigger is better? Is "portion control" a user-friendly term?
"We are still perplexed by communication and even fundamentally understanding what an appropriate portion size looks like," Fisher, the conference organizer, said afterward.
"How do we talk to people about this?"
Portion Size Quiz
Are your estimates of portion sizes stuck in the past? Test your accuracy: http://1.usa.gov/1gpVrW1