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Human Studies http://commentator.tufts.edu/archive/wt_ One purported reason that
a higher protein diet may enhance weight loss is via an appetite
suppressing effect. The following research articles investigated
this effect. Barkeling, B Rossner, S, Bjorvell, H. Effects of a high protein meal (meat) and a high carbohydrate meal (vegetarian) on satiety measured by automated computerized monitoring of subsequent food intake, motivation to eat, and food preferences (1990) Int J Obes 14:743-751. A high protein meal with meat resulted in greater satiety than a high carbohydrate vegetarian meal in a study of 20 women. Those given the meat meals ate 12% less and at a slower rate than those given the carbohydrate meal. Both meals resulted in an aversion for high protein foods after the meal, but this was aversion greater for the meat group.
De Graaf, D, Hulshof, T, Westrate, JA, Jas, P. 1992 Short-term effects of different amounts of protein, fats, and carbohydrates on satiety. AJCN 55:33-38. Twenty-nine non-obese female participants consumed liquid meals that varied in calorie and macronutrient (100, 250, 400 kcal; 99% CHO, 92% fat, 77% pro) composition. Alterations of macronutrient composition had no effect on subjective ratings of satiety; however, the higher calorie meals did have a greater effect than lower calorie meals.
Hill, AJ, Blundell, JE. (1986) Macronutrients and satiety: The effects of a high protein or high carbohydrate meal on subjective motivation to eat and food preferences. Nutrition and Behavior 3:133-144. In a study of 13 young non-obese males and females participants were given 500 kcal meals of a mixed diet, either 52% cho/15% pro or 21%cho/31% pro. While the high protein meal resulted in greater satiety according to a subjective scale, the high protein meal had a 10 g higher fat content . Fat is known to have a satiating effect. Therefore, a direct link between protein and satiety cannot be established from this study.
Teff, K, Young, SN, Blundell, JE. 1989 The effect of protein or carbohydrate breakfasts on subsequent plasma amino acid levels, satiety, and nutrient selection in normal males. Pharmacology Biochem and Behavior 34:829-837. Participants (32 males, age 18-30, all within 10% of ideal body weight) were fed a breakfast of high carbohydrate or high protein pudding in a double-blind crossover design. Three hours later, they self selected lunch from a buffet. There was no significant difference in food consumed between the high carbohydrate and high protein breakfast groups. However, the high carbohydrate breakfast had twice as many calories as the high protein breakfast, which indicated a possible satiating effect of protein. In the second half of this study, subjects were fed an isocaloric 400 kcal pudding with 0, 4, 8, or 12% protein. Plasma amino acids were measured before and after the meal. Only the 0% protein meal resulted in an increased tryptophan:large neutral amino acid ratio.
Rolls, BJ, Hetherington, M, Burley, VJ. (1988) The specificity of satiety: The influence of foods of different macronutrient content on the development of satiety. Phys and Behvior 43: 145-153. In this study, 10 women, mean age 23 and mean BMI 21, were fed five different isocaloric preload meals (high carb-starch, high carb-sugar, high fat, high protein, mixed meal, after which they rated hunger level and self selected a follow-up meal. Ratings of hunger decreased and fullness increased following the high starch and high protein preloads to a greater degree than the high fat, high sucrose, and mixed preloads. In the self-selected meal 2 hours after the preload, energy intake and preference for high carbohydrate and high fat food items were signifiancly decreased by the high protein and high starch preloads.
Ludwig DS, Majzoub JA,. Al-Zahrani A, Dallal GE, Blanco I, Roberts S. (1999)High Glycemic Index Foods, Overeating, and Obesity Publication: Pediatrics;103:March See http://commentator.tufts.edu/archive/wt The glycemic index (GI) is a measure that quantifies the rise in blood glucose that occurs after eating a carbohydrate-containing meal. Most starchy foods commonly eaten in North America, chiefly refined grain products and potatoes, have a high GI, exceeding even that of table sugar. By contrast, vegetables, legumes, and fruits generally have a low GI. Using a crossover study design, metabolic changes and voluntary food intake were observed among 12 obese adolescent boys in the hours following ingestion of one of three standard test breakfasts that varied in dietary GI. The high-GI meal was associated with higher serum insulin levels, higher plasma epinephrine, lower plasma glucagon levels, lower post-absorptive plasma glucose and lower serum fatty acid levels, compared to the low-GI meal. Voluntary energy intake and self-reported hunger were substantially greater after the high-GI meal compared with either the medium- or low-GI meal.
One important consideration in the studies on protein and satiety is that the studies utilized non-obese individuals, and satiety response to macronutrient composition may be different between the obese (or a subset thereof) and non-obese.
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