One purported reason that
a higher protein diet may enhance weight loss is via an appetite
suppressing effect. The following research articles investigated
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
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
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
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.