The study examined the energy content (in calories) of a variety of foods from sit-down and fast food restaurants and frozen convenience meals from the grocery store.
A sample of their findings:
- P. F. Chang's Sichuan-style asparagus (large) - Stated calories: 260. As tested: 558
- Denny's grits (served with butter) -- Stated calories: 86. As tested: 258
- Taco Bell express taco salad (chicken) -- Stated calories: 328. As tested: 607
- Lean Cuisine shrimp and angel hair pasta -- Stated calories: 250. As tested: 319
- Bell & Evans grilled chicken breast -- Stated calories: 80. As tested: 145
- Domino's thin crust cheese pizza (large), per serving -- Stated calories: 212. As tested: 141
- Ruby Tuesday toast -- Stated calories: 171. As tested: 110
At least the calorie content of these frozen convenience meals is regulated by federal law. The nutrition in a restaurant meal is left up to state control. One of the researchers, Susan B. Roberts, PhD, professor of nutrition at Tufts University and author of "the "I" diet," told me in an e-mail that "To my knowledge the oversight on calories is minimal. We talked to a few inspectors who did not want to be named, and it appeared it wasn't a priority to say the least."
Restaurant meals are usually prepared by hand and subject to normal human variability, so if no one is making sure the promised portion size and contents are followed strictly, we can expect that these dishes will vary a great deal. If you've ever ordered just before closing time at a restaurant, you may well have seen what happens to portion control when the cooks decide that they don't want good food to go to waste, and load up your plate.
The study also found that, while some restaurants offer low-calorie entrees, they fail to include the calories from the free side dishes, which, in some cases, exceed those of the entrée itself.
Based on its sampling, the study concluded that low-calorie restaurant offerings and low-cal frozen convenience meals are frequently higher in calories than stated, although the latter still falls within the rather broad federal regulations for accuracy. For a dieter trying to shed some pounds, underestimating the calories of what he eats by 20% can prolong the misery unnecessarily.
Other studies have found even larger disparities between stated and actual calorie content of restaurant food, so I anticipate more research in this area.
My take? Prepared food is inherently variable, and expecting accuracy in your food equal to that of pharmacy dosages is impractical. Take restaurant nutritional information with a large dose of salt (metaphorically), and don't forget to count the calories of those free bread sticks, corn chips and grits.
Roberts suggests, "Factor in that when you eat out you are probably getting 20% more calories than you think, and 10% for frozen meals. Those numbers may be a bit rough but if you are watching your weight it is better to err on the side of assuming things have more than you think."
If you really want to know what you're eating, fix it yourself, and measure carefully.