Although people could use scales or measuring cups, "people don't like to," says Laurie Acosta, one of the designers and the dietitian for the EZ Weight Plate. "They want something easier."
Last year, the Archives of Internal Medicine published the first, and so far the only, study of a portion-control plate -- the Diet Plate. Available in male and female versions (the latter intended to yield lower-calorie meals), the Diet Plate is divided into sections for carbohydrates, proteins, cheese and sauces, with the rest of the space for vegetables.
All study participants were obese, had Type 2 diabetes and were required to eat most of their meals at home. Of the original 130, 122 completed the six-month study. The group using the Diet Plate lost more weight overall than the group who didn't use the plate. A greater proportion of those using the plate lost at least 5% of their weight -- an amount that's been shown to have significant health benefits -- and more of them were able to lower the levels of medication they were taking to treat their diabetes.
However, the study also may have revealed some limits on what portion-control plates can do. "This is a population who are highly motivated to lose weight so they can reduce meds, and yet only 17% lost more than 5% [of their weight]," says Roberts of Tufts University. "I know that will have some health benefits, but in terms of the big picture, it isn't a whole lot."
--
More than serving size
The basic concept underlying portion-control plates -- if you eat less, you'll weigh less -- is beautiful in its simplicity. "And considering what people eat, anything smaller would be better," says Ruth Frechman, spokeswoman for the American Dietetic Assn. in Burbank.
But many experts caution that the concept is a little too simple and that it matters what you have a portion of.
"Calorie density," Rolls says, "has an even bigger effect."
Portion-control plates take density into consideration somewhat. They often come with information about healthful eating, even sample menus. And calorie-dense carbs and proteins are given much less space than low-carb veggies, for instance. But on one of these plates, a piece of steak is equivalent to a piece of white fish if both fit into the allotted room. Steak and white fish are far from equivalent calorically.
