Serving Size and Waist Size

G. Douglas Andersen, DC, DACBSP, CCN

In the spring of 2003 I wrote a 4-part series on U.S. food consumption and obesity.1,2,3,4 I included many tables full of disappearance data derived from the National Health and Nutritional Examination Surveys. Although it was in contrast to what many famous diet book authors contend, my opinion and conclusion was that the obesity problem is caused by too much of everything. Granted, disappearance data is far from exact, but the expansion of our waistlines seemed to parallel the amount of food in that data. (Which also included examples of how much serving sizes have grown.)

Since I wrote my series, the evidence for my complex theory that weight gain may be related to caloric intake has been building.5,6,7,8

I came across a small study that adds to my theory.9 Thirteen college students, 9 males, 4 females, were recruited for what they thought was a 2-week study on food taste enhancers and the perception of certain foods. On a Monday, Wednesday, and Friday a lunch buffet was set up for them. They were instructed to take and eat as much food as they wanted. Their plates were weighed and analyzed before their meal. When they finished, researchers again analyzed anything left on their plates. During week 1 on the study days they also kept a food and activity diary. In the second week they were divided into 3 groups. This time, the food they received was given to them by the researchers. It was based on the average of what and how much they had consumed during their 3 buffet meals the previous week. They were instructed to follow their food and activity diaries from week 1. That is, eat the same type and quantity of food they had in the previous week and maintain the same activities that were listed in their diaries. The subjects had the impression this was needed to rule out any effect different foods, portions, or activities would have on their "taste enhancement and food perception," which was supposedly being studied during their lunches. In reality, researchers were studying what effect serving size had on the amount consumed.

Table 1
  Monday Wednesday Friday
Week 1 Buffet Lunch Buffet Lunch Buffet Lunch
Week 2 Group 1 (100%)
Group 2 (125%)
Group 3(150%)
Group 1 (150%)
Group 2 (100%)
Group 3(125%)
Group 1 (125%)
Group 2 (150%)
Group 3(100%)
Percentages refer to portion size as determined by the average of the amounts consumed ad libitum in week 1.

In Table 1, the 100% meal was an average of the amount they self-selected in week 1. Then, 25 or 50% more of the same types of foods were added to their plates on various days. Results showed that the average calories on the 100% days were 698. They ate 863 calories when their plates contained 125% of the foods they had self-selected and 971 calories on the days their plates contained 150% of the amount they had originally selected. The amount of food both males and females consumed was not associated with hunger. It was, in all cases, directly associated with portion size.

This study was far from perfect and had plenty of limitations including 1. a small sample size, 2. supervision only on the test meal, and 3. a short duration. However, it does make one stop, pause and consider the remote possibility the more they give us, the more we eat.


1Andersen, G.D. U.S. Food Consumption and Obesity, Part 1. Dynamic Chiropractic. March 24, 2003; 21(7): 50.
2Andersen, G.D. U.S. Food Consumption and Obesity, Part 2. Dynamic Chiropractic. April 21, 2003; 21 (9): 40.
3Andersen, G.D. U.S. Food Consumption and Obesity, Part 3. Dynamic Chiropractic. May 19, 2003; 21 (11): 58.
4Andersen, G.D. U.S. Food Consumption and Obesity, Part 4. Dynamic Chiropractic. June 13, 2003; 21 (13): 22.
5Wansink, B. Environmental Factors that Increase the Food Intake and Consumption Volume of Unknowing Consumers. Annu. Rev. Nutr. 2004; 24: 455-479.
6Rolls, B.J., Roe, L.S., Kral, T.V., et al. Increasing the Portion Size of a Packaged Snack Increases Energy Intake in Men and Women. Appetite. 2004; 42: 63-69.
7Kral, T.V., Roe, L.S., Rolls, B.J. Combined Effects of Energy Density and Portion Size on Energy Intake in Women. Amer. J. Clin. Nutr. 2004; 79: 962-968.
8Rolls, B.J., Roe, L.S., Meengs, J.S., Wall, D.E. Increasing the Portion Size of a Sandwich Increases Energy Intake. J. Amer. Dietetic Assoc. 2004; 104: 367-372.
9Levipsky, D.A., Woun, P. The More Food Young Adults are Served, the More They Overeat. J. Nutr. 2004; 134: 2546-49.


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