In the satiety study (Study 2), soy and wheat pretzels containing
239 kilocalories (1000 kJ) were consumed. Despite the
soy pretzel having 5.2 more grams of protein and 2.2 more grams
of fiber than the wheat pretzel, there was no statistical difference
in the feeling of satiety (Fig. 2). The large variation in satiety
scores stems from the subjectivity of the assessment. To account
for this, we used a cross-over design so that we could compare the
satiety values directly from each individual. A pattern was not
observed between satiety declarations after consumption of the
wheat or soy pretzel. There were likely counteracting factors that
led to this observation. Protein both stimulates the release of
cholecystokinin (CCK), which inhibits gastric emptying.The
increase in fiber can increase chyme viscosity, which leads to
slowed gastric emptying and/or an increase in thirst which
expands the stomach, leading to release of CCK, thus increasing
satiety.However, the wheat pretzels were larger in appearance
due to the facilitated formation of air cells from higher gluten
concentrations, and may have subconsciously increased satiety.A study that includes a larger number of participants and can
control for physical activity, food intake on days before the
experiment, alcohol consumption, and sleep amount and quality may be able to detect subtle differences, if there are indeed any,
between the satiety of these snack foods.