Health & Nutrition Bites

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More on small dietary changes

Today's Health and Nutrition Bite is an interesting, larger-scale application of the outcomes of several different avenues of research into portion size, calorie density, and overall food consumption.

In past Bites we've seen that when adults are served larger portions of a snack food - whether healthy or less healthy - they consumed about 30% more of the given snack by weight. Another Bite concluded that "if you aren't knowingly depriving yourself, you're likely to be just as satisfied with a smaller portion as a larger one," and another that "[study participants] believed that they would eat less at every point during the low-energy-density meal days as compared to the high-energy-density days," showing that foods that are lower in energy density (fewer calories per ounce by weight - think carrots vs. chocolate) are just as satisfying as foods that are higher in energy density.

Researchers in the United Kingdom wondered if subtly altering the mix of high-energy-density and low-energy-density foods available at workplace cafeterias might have an effect on the number of overall calories purchased by workers (PLoS Med 18(9): e1003743).

They recruited a major UK supermarket chain to participate and selected 19 cafeterias with electronic point-of-sale registers in distribution centers (not supermarkets) across England, Scotland, and Wales. The number of employees served at each site ranged from 561 to 2,357 staff members for a total of 20,327 staff served by the 19 cafeterias. All the distribution centers selected were located in comparatively remote regions, where the dining options were either the cafeteria, vending machines, or bringing food from home.

The authors worked closely with the three different catering companies responsible for proving meals at the 19 locations to cut the availability of higher-calories foods by about 10%, replacing them with similar, lower-calorie foods. This was applied to 7 varieties of items: main dishes (e.g. lasagna); side dishes (rice); cold drinks such as sodas; sweet snacks such as candy bars; savory snacks such as potato chips; desserts such as pre-measured chocolate mousse, and bakery items such as pre-measured slices of cake.

The number of items available for purchase did not change - only the mix of higher versus lower calorie products.

After a baseline period to assess the normal purchasing habits of each location, the cafeterias implemented the change in availability for 8 weeks, tracking purchases all the while.

Then the authors and catering companies implemented an additional change on top of the decrease in availability of higher-calorie foods: they also cut portion sizes (by volume) by a minimum of 10% (14% on average overall) for main meals, sides, desserts, and bakery items that were considered to be higher in calories compared to other products in the same category.

The implementation of the smaller portion sizes was rolled out gradually across the 19 cafeterias, such that not all cafeterias carried the smaller portion sizes as well as the decrease in available for the same length of time. The period in which the cafeterias combined both reduced availability and reduced portion size was a minimum of 4 and up to 13 weeks over the course of a 25-week study.

With the purchase records from the registers at the cafeterias, the authors were able to compare what was bought during the baseline period and compare that with the periods of reduced availability - and then with the periods of both smaller portion sizes and reduced availability.

The authors acknowledge that because they don't have purchase records for individuals - only daily totals for each item purchased - they can't draw conclusions about individual purchasing decisions. That said, their analysis showed that the total number of calories purchased in the cafeterias per person per day fell by 4.8% during the reduced availability period. This grew to 11.5% when the smaller portion sizes were implemented in conjunction with the reduced availability of higher calorie items.

A couple of things we found interesting in this study. First, not all cafeterias had the same outcomes: some saw larger effects than others, possibly due to the relatively small changes. Second, "once the study started, very few comments or complaints were brought to our attention."

What this means for you

For someone consuming 1500 calories per day, cutting 4.8% of calories means consuming just 72 fewer calories per day. That doesn't necessarily mean losing weight, but that's not the point.

The message we'd like you to take from this is that small changes - like choosing lower-calorie versions of some items or taking a slightly smaller portion - can have a cumulative impact.

And it looks like you're unlikely to notice.

First posted: February 16, 2022