The new idea about the causes of obesity is simple and probably won't surprise you: We have too many food choices — from Pad Thai to pasta with pesto to fish tacos with rice and beans. And this is one reason we are eating too much.

Consider the size of grocery stores and the aisles and aisles of different foods. The options you have when it comes to frozen pizza, breakfast cereal, or even bread are mind-boggling.

A newly published study from the University of Liverpool looked at how all these choices may be laying waste to our waistlines.

Researchers used pepperoni pizza as their test food because it is sold under numerous brand names that vary greatly in calorie count. They wanted to see the impact that multiple varieties of the same product can have on food consumption and satisfaction.

The nearly 200 people in the study reported they ate over 70 different brands of pepperoni pizza. The pizzas came from grocery stores and take-out restaurants.

Some people regularly consumed the same brand of pepperoni pizza; others ate many brands.

The calorie count of the pizzas varied widely — from 501 to 1909 calories per pizza, a nearly 400 percent difference. That's where the trouble began.

People who varied the brand of pizza they ate considered it less filling compared to people who stuck with one brand. Those who consumed multiple brands were also more likely to overeat to avoid feeling hungry later. Because they ate so many brands of pizza, researchers believe their perception of how much they had eaten was distorted.

“It would appear that this high variability of food items makes it more difficult for people to learn about food and manage their consumption which exposes a new feature of Western diets and which has potential public health implications,” said author Charlotte Hardman in a statement.

Though pizza was used in this study, the results could be applied to any food that comes in different brands and with differing calorie counts even salads.

The message is pretty clear. Find the healthiest brand of (fill in the blank) that you and your family enjoy, and stick with it.

The study is published in PLOS ONE.