“Eat in moderation.” It’s a clarion call for healthy eating and touted as an effective way to lose weight.

The idea: Depriving yourself of foods that you love is old-fashioned advice. It’s better to eat what you like, including your favorite high-calorie foods—but not too much.

Here’s a secret: It’s a trap. And it may be making you fat, according to a new paper published in the peer-reviewed journal Appetite.

WHAT IS “MODERATION”?

On the fast-food chain Chick-fil-A’s bags for takeout food, there was this statement…

“Moderation Is Key: All foods can fit within a healthy diet if consumed in moderation. With appropriate portion sizes and physical activity, you can enjoy treats like our Frosted Lemonade.”

Moderation is one of many myths that Big Food uses to rationalize their calorie, fat and sugar bombs. (That Frosted Lemonade from Chick-fil-A contains 63 g of sugar, the equivalent of 16 teaspoons.) But according to new research, food companies that proselytize moderation are not the core of the problem. The real problem is you.

Most people have no idea what moderation in eating really means—and find it easy to twist the idea unconsciously to excuse overeating. To learn more, we spoke with psychologist Michelle vanDellen, PhD, an assistant professor in the behavioral and brain sciences program at the University of Georgia.

THE REAL-LIFE TEST

A series of telling studies examined how people think about moderation, especially when it comes to foods that they know they should limit such as cookies, fruit-shaped gummy snacks, soda, pizza and fast food. The findings below held true for both men and women…and normal-weight and overweight people…

  • Most people define “eating moderately” as eating a bigger amount than they think they should eat. For example, in one study, subjects were presented with a big plate with 24 cookies and asked how many a person should eat—and how many would constitute eating in moderation. On average, they said a person “should” eat about two cookies, but that “moderation” was a little more than three cookies.
  • The more you like a food, the bigger a “moderate” portion will be for you. In another study, subjects were shown a picture of gummy snacks. The more a person liked gummy snacks, the researchers found, the bigger the “moderate” portion tended to be.
  • The more often you eat a particular kind of food, the more frequent you’ll consider moderation to be. In a third study, the researchers asked subjects how often over two weeks they ate 12 different high-calorie foods, including pizza and soda. No matter how often people ate a particular food, they consistently defined “moderate” frequency as more frequent than what they themselves did! Thus, if you eat ice cream twice a week, you might define moderate as four times a week.

These malleable definitions are likely contributing to the obesity epidemic—by encouraging overeating. The crucial moment occurs when you’ve eaten a portion of a food that you know isn’t really good to eat a lot of. That’s when you must decide if eating more would be going overboard.

To gain control over overeating, explains Dr. vanDellen, you need to recognize that you have a conflict at that moment—you would really like to eat another piece of pie, but you know you shouldn’t. If you delude yourself that you’re eating “moderately,” you’ll never feel that conflict—and you’ll just keep eating.

MASTERING MODERATION

While there are many contributors to our obesity epidemic, including sugar and other low-fiber refined carbs, there’s strong evidence that the increasing size of portions is a major culprit. That’s not to say you should radically cut down on how much you eat—this almost always backfires.

Ironically, however, paying attention to the actual amounts of foods that you eat may be the best way to truly eat in moderation. To illustrate this, let’s go back to that Frosted Lemonade mentioned earlier. It’s a 16-ounce, 330-calorie cup of lemonade blended with ice cream.

If you think of it as ice cream, and know your serving sizes, you would realize that a serving size for ice cream is one-half cup—four ounces. For juice, a serving size is six ounces.

So instead of drinking the entire 16 ounces, let’s say you enjoy six ounces—three-quarters of a cup. You’ll get about 125 calories and 24 g of sugar. It’s still a high-sugar treat, but a more manageable one…and perhaps even “moderate.”