With a quarter of daily calorie intake in the Western world – especially in Israel – derived from snacks that are not nutritious and even harmful to health, ways have to be found to encourage reducing their intake and replacing them with unprocessed and natural food.
Researchers at Pennsylvania State University have found that the size of an individual snack piece not only influences how fast a person eats it, but also how much of it they eat. What they learned can have implications for helping people better understand how eating behavior impacts calorie and sodium intake.
The team of food scientists led by Madeline Harper, a graduate student in food science, working with Prof. John Hayes who was corresponding and director of the Penn State Sensory Evaluation Center, published their findings in the journal Appetite under the title “Unit size influences ad libitum intake in a snacking context via eating rate.”
They investigated how the size of pretzels influences eating behavior –overall intake, eating rate, bite size and how long they snacked – and found that people eat larger pretzels quicker with larger bites. They also found that while people ate smaller pretzels slower and with smaller bites and ate less overall, they still had higher intake of sodium (salt).
How the study was performed
Seventy-five adults participated in the study, eating snacks three different times in the Sensory Evaluation Center. The oversized snack was about 2.5 servings of one of three sizes of pretzel – small, medium or large. To calculate eating rate and bite size, the researchers video recorded each snacking session, noting how many minutes each person spent snacking and their number of bites along with how much each participant ate in both weight and calories.
When participants were given the same amount of food, how much they ate — in both snack weight and calories — depended on unit size, with study participants consuming 31% and 22% more of the large pretzels compared to the small- and medium-sized pretzels, respectively. Size of the pretzel also influenced eating rate and bite size, with the largest pretzel size yielding the fastest eating rate and largest mean bite size.
The researchers also reported that, after accounting for eating behavior, the pretzel size alone did not significantly affect how much a person ate, suggesting the eating behavior the different pretzel sizes prompted was driving total intake. Their results suggest larger pretzel size induces a person to eat more quickly and take bigger bites.
Together, they proved that unit size influences intake by affecting eating behavior and that food characteristics such as unit size can be manipulated to moderate snack intake, Hayes explained. “Food structure – texture, size and shape – can be used to modulate eating behavior and food intake,” he said. “Food geometry, specifically unit size, is particularly useful for snack foods. We’re interested in how the material properties of foods can be harnessed to help people eat less without impacting their enjoyment.”
The relationship between pretzel size and sodium intake was obvious to the layman but previously overlooked by researchers, Harper explained. Eating more smaller pretzels likely results in higher consumption of salt. The smaller size has more surface area for the same weight, so the researchers hypothesize that more total salt on the surface means that a snacker would consume more sodium when eating them.
“So, we’re suggesting that if you’re trying to watch your calorie intake or are trying to reduce the amount that you’re eating in a snack, maybe a smaller pretzel would meet your needs better, because of the inherent way the size of the pretzel affects your eating rate,” Harper added. “But if you're more worried about hypertension from the amount of sodium you’re consuming, the larger pretzel would be better for you, because you’ll consume less salt even though you would consume more grams of pretzel.”