The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


Study compares americans' eating behaviors over 30 years

Posted in
Eat better

Friday, Jul 22, 2011

Researchers at the University of North Carolina at Chapel Hill recently set out to determine which of these three factors explain why we are eating more calories today than we ate 30 years ago1:

  1. Increases in the frequency of eating/drinking occasions, especially snacking
  2. Increases in the typical portion sizes of foods and beverages
  3. Changes in the energy density (number of calories in a specific amount of food) of the foods consumed; for instance, 1 ounce of cheese has 115 calories vs. 1 ounce of grapes has 20 calories
Evaluation of data from large national studies conducted in 1977-78 (Nationwide Food Consumption Survey), 1989-91 (Continuing Survey of Food Intakes of Individuals), 1994-98 and 2003-6 (National Health and Nutrition Examination Surveys) found the following:
  • Between the late 1970s and 2006, Americans increased their calories by 570 calories per day
  • Over the 30-year period, Americans increased their eating occasions by 1.1 per day
  • While portion size increased significantly between the 1977-78 and 1994-98 surveys, it then dropped slightly between the 1994-98 and 2003-6 surveys
  • Energy density remained steady between the 1977-78 and 1989-91 surveys, then declined slightly between the 1989-91 and 1994-98 surveys
Thus, researchers concluded that while all three factors listed above have contributed to some extent to 30-year changes in Americans' total calorie intake, changes in eating occasions and portion sizes have accounted for most of the change. And while large portion sizes may have driven the rise in calories during the early part of the study period, today, eating occasions may be driving this rise. Think about it. How many times a day do you eat? While some people think it's healthier to spread eating throughout the day, others argue that this should only be done if meals are small and snacks are very small (100 calories or less) and healthy (like fruits and vegetables). Unhealthy foods are everywhere and eating three medium-to-large meals plus several snacks or bites here and there can easily put you over your daily calorie needs.

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1Duffey, K.J., & Popkin, B.M. (2011). Energy density, portion size, and eating occasions: contributions to increased energy intake in the United States, 1977-2006. PLoS Med, 8(6), e1001050.