The obesity epidemic continues worldwide and is considered a major health concern. A shift back to consumption of whole foods may be an important part of the solution in the current rising obesity trend. Both protein and fiber have satiating properties, but few studies have examined whether their impact on different biological mechanisms work additively to more strongly enhance the overall satiety potential of a meal. In the first study, the objective was to determine the effects of a high protein meal (beef) compared to a moderate protein, high fiber meal (beans) on subjective appetite and energy intake at a subsequent meal. We hypothesized that a moderate protein, high fiber meal containing beans would be as satiating as a high protein meal containing beef. Twenty-eight adults, 14 men and 14 women participated in this randomized, controlled study in which subjects consumed two test lunches including a "meatloaf" made from either beef or beans. The primary outcome was to observe satiety ratings using visual analogue scales to assess hunger, satiety, fullness, and prospective food intake. Secondary outcomes included: food intake at the subsequent meal offered in the form of snacks, gastrointestinal tolerance, and palatability of the meals. No difference between the beef and bean was observed for appetite ratings over 3 hours, food intake at the subsequent meal, or sum of GI score. Gas and bloating were reported more often after the bean meal than the beef meal. The conclusion to this first study was that a beef-based meal with high protein and a bean-based meal with moderate protein and high fiber produced similar satiety, while the bean-based meal resulting in higher, yet moderate, gas and bloating.In the second study, we examined the effect of egg alone and in combination with whole grains compared to a refined ready-to-eat cereal on satiety and food intake in human subjects. We hypothesized that breakfast meals containing eggs, both high protein with white toast and moderate protein with whole grain toast containing fiber, would result in increased satiety ratings compared to an isocaloric standard refined cereal breakfast. Forty-eight adults, 24 men and 24 women, participated in this randomized, cross-over study. We designed whole food diets, controlled for macronutrients. The primary outcome was to observe satiety ratings using visual analogue scales to assess hunger, satiety, fullness, and prospective food intake. Secondary outcomes included: post-prandial blood glucose response, food intake at the subsequent meal offered in the form of an ad libitum pizza lunch, gastrointestinal tolerance, and palatability of the meals. No difference was observed between the cereal and egg + whole grain toast breakfasts for AUC for all satiety ratings however the egg + white bread breakfast was significantly improved for all 4 satiety ratings. Lunch intake was significantly reduced in both egg breakfasts compared to the cereal breakfast. No difference was observed for the sum GI score between the egg + white toast, egg + whole grain toast and cereal breakfasts, however gas and bloating was significantly higher for the egg + white toast breakfast compared to the cereal meal. Food intake at the subsequent meal was reduced for both egg breakfasts compared to the cereal breakfast. The results from these studies support the hypothesis that protein and fiber contained within whole foods results in greater satiety than refined carbohydrate foods. Protein, with and without fiber, produced the greatest satiety outcomes suggesting that the incorporation of high protein foods into the diet, specifically for breakfast, may result in greater feelings of satiety that could lead to decreased food intake and weight loss over time.
University of Minnesota Ph.D. dissertation. June 2014. Major: Nutrition. Advisor: Joanne L. Slavin. 1 computer file (PDF); ix, 109 pages, appendices A-I.
Effects of the combination of protein and fiber in whole foods on satiety, blood glucose response and food intake in humans.
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