Effects of Fiber and Food Form on Satiety and Energy Intake in Healthy Human Subjects

Abstract

Satiety is a complex process influenced by a number of properties in food such as physical form, macronutrient content, visual appeal, taste, pleasantness, smell and aftertaste. From past research, we already know that the liquid form of food produces a weaker satiety response compared to the solid form of food. On the other hand, little is known about the effects of different types of solid food (i.e. solid food in the form of an energy bar vs. solid food as part of a meal) on satiety and subsequent energy intake. The following work describes two intervention studies designed to help explain the influence of various properties of food on satiety. In the first study, we hypothesized that a 10g dose of oat bran fiber or a 10g dose of barley bran fiber in a breakfast bar would enhance satiety more than a control bar with 3g of wheat fiber. We also hypothesized that consumption of the oat bran bar or barley bran bar for breakfast would reduce energy intake at an ad libitum lunch more than the wheat fiber breakfast bar. Secondary outcomes were to determine if the oat and barley bran fiber bars had any effect on gastrointestinal tolerance and colonic fermentation. Finally, we sought to determine if any of the fiber bars differed in their palatability ratings. Healthy women (n=42) participated in this randomized double-blind, crossover study comparing satiety after they consumed three different breakfast bars: one with barley bran fiber, one with oat bran fiber and a bar with low amounts of wheat fiber (control). Women used 100 mm visual analog scales (VAS) to rate satiety for 4 hours after breakfast bar consumption. Satiety did not significantly differ among treatments nor did energy intake, colonic fermentation, and gastrointestinal tolerance. In the second study, we hypothesized that a high protein pasta would increase satiety and decrease mid-afternoon snacking more than a high fiber pasta or a control. We also investigated whether or not the added ingredients to the pasta would have any effect on gastrointestinal tolerance, food intake and palatability. Healthy men (n=18) and healthy women (n=18) participated in this randomized double-blind crossover study. Subjects consumed three different pastas (high protein, high fiber, or control) for lunch at noon and proceeded to rate satiety with VAS over a three-hour period. Ad libitum snacking was assessed at 3:00pm and subjects rated any gastrointestinal symptoms and their food intake for the remainder of the evening. Once again, satiety did not significantly differ among the treatments, nor did gastrointestinal tolerance. A gender-treatment interaction was observed for food intake and men consumed significantly more calories after the high protein pasta compared to the high fiber and control pasta. We also found differences in palatability among the pastas, which suggests that hedonic properties of food may influence satiety ratings and subsequent food intake. The results from these two studies do not support a connection between the consumption of whole foods and satiety. Changing the satiating properties of whole foods by adding more protein or fiber was a limitation in both studies because it affected our palatability ratings. Other limitations that may have contributed to these null results are a short intervention time and too small a dose of fiber and protein.