The saying goes that you can’t judge a book by it’s cover.  It appears that you may not be able to believe the calorie content posted on the packaging of frozen foods or the menus of some restaurant chains either.  If you do, you might find that attaining calorie balance is hard to do.  Here’s why.

In a study published last week, researchers found that on average, fast food (i.e., Taco Bell, McDonald’s, Wendy’s, Domino’s, Dunkin Donuts) and family-style restaurants (such as Denny’s, Ruby Tuesday, P.F. Chang’s, Olive Garden, Applebee’s) underreported the calorie content of certain entrees by 18 percent on average¹.  Researchers very precisely analyzed the calorie content of 29 restaurant meals using a bomb calorimeter and compared the results with what the food manufacturers  stated on their menu or web sites.  Some were right on (Taco Bell Crunchy Beef Taco at about 190 calories).  Others were way – like 200 percent! – off.  For example, Denny’s grits (served with butter) were measured at 258 calories whereas the stated amount for grits was 86 calories. 

And these inaccuracies are just for the entrees.  Many of the entrees had side dishes for which the calorie content was not counted.  On average, the side dishes added nearly 500 calories to the entrée calorie level.

Did frozen dinners fare any better?  Yes, a bit.  The calorie content of frozen dinners was under reported by 8% on average. 

Before you get all steamed up about the lack of truth in advertising for food, you should know that no one regulates calorie content advertising in restaurants.   So it is kind of amazing that 11 of the 29 restaurant entrees came in at 10% or less from the stated calorie content.  As for packaged meals such as frozen dinners, the Food and Drug Administration allows food manufacturer’s 20 percent leeway on calorie content.  Only 3 of the 10 frozen dinners exceeded this amount.

Use the 20 Percent Rule

So a couple of caveats are needed.  First, this study only looked at 39 foods from 15 different restaurants or food manufacturers.  This is a tiny bite of all the commercially-prepared entrees.  Second, the researchers only purchased only one unit of each food item so it is not known if the measured error would be repeated in duplicate samples.  Obviously more research is needed to know just how far off stated calorie counts are from what is actually provided in an entrée.

Nonetheless, this small study gives us a peek at a potential problem when it comes to calorie balance.  Namely, your calorie tracking may be inaccurate if you have been relying on the calorie information provided by food manufacturers.  A 20 percent error on a 500 calorie entrée is an extra 100 calories that you may not know you are eating.  That’s about a mile of brisk walking.  And if you don’t balance out those extra calories with physical activity, it can mean added pounds or at the very least, frustration that your calorie tracking is not working.

One possible solution is to automatically add 20 percent to the total calorie content stated on the menu of restaurant entrees.  Or you can just not eat one-fifth of the entrée.  Similarly, add 10% more calories than stated on the package for frozen entrees or skip one-tenth of the frozen entrée.   Because of the wide variability in the accuracy of what is on the label and what is in the food calorie-wise, this is a rather crude way of coping with the problem.  But if you don’t take some action, you may find yourself scratching your head as why your calorie-counting efforts aren’t paying bigger dividends.

¹ Urban LE, Dallal GE, Robinson LM, et al.  (2009) The accuracy of stated energy content of reduced-energy commercially prepared foods.  Journal of the American Dietetic Association.  110:116-123.