Higher protein diets reduce ad libitum caloric intake

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Here are a couple of abstracts describing how higher-protein diets

(30% protein) reduce caloric intake. There may be some lessons here

for CR practitioners.

Tony

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Am J Clin Nutr. 2005 Jul;82(1):41-8.

A high-protein diet induces sustained reductions in appetite, ad

libitum caloric intake, and body weight despite compensatory changes

in diurnal plasma leptin and ghrelin concentrations.

Weigle DS, Breen PA, Matthys CC, Callahan HS, Meeuws KE, Burden

VR, Purnell JQ.

University of Washington School of Medicine, Seattle, WA, USA.

weigle@...

BACKGROUND: Ad libitum, low-carbohydrate diets decrease caloric

intake and cause weight loss. It is unclear whether these effects are

due to the reduced carbohydrate content of such diets or to their

associated increase in protein intake. OBJECTIVE: We tested the

hypothesis that increasing the protein content while maintaining the

carbohydrate content of the diet lowers body weight by decreasing

appetite and spontaneous caloric intake. DESIGN: Appetite, caloric

intake, body weight, and fat mass were measured in 19 subjects placed

sequentially on the following diets: a weight-maintaining diet (15%

protein, 35% fat, and 50% carbohydrate) for 2 wk, an isocaloric diet

(30% protein, 20% fat, and 50% carbohydrate) for 2 wk, and an ad

libitum diet (30% protein, 20% fat, and 50% carbohydrate) for 12 wk.

Blood was sampled frequently at the end of each diet phase to measure

the area under the plasma concentration versus time curve (AUC) for

insulin, leptin, and ghrelin. RESULTS: Satiety was markedly increased

with the isocaloric high-protein diet despite an unchanged leptin AUC.

Mean (+/-SE) spontaneous energy intake decreased by 441 +/- 63 kcal/d,

body weight decreased by 4.9 +/- 0.5 kg, and fat mass decreased by 3.7

+/- 0.4 kg with the ad libitum, high-protein diet, despite a

significantly decreased leptin AUC and increased ghrelin AUC.

CONCLUSIONS: An increase in dietary protein from 15% to 30% of energy

at a constant carbohydrate intake produces a sustained decrease in ad

libitum caloric intake that may be mediated by increased central

nervous system leptin sensitivity and results in significant weight

loss. This anorexic effect of protein may contribute to the weight

loss produced by low-carbohydrate diets.

PMID: 16002798

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Cell Metab. 2005 Nov;2(5):321-9.

Portal sensing of intestinal gluconeogenesis is a mechanistic link

in the diminution of food intake induced by diet protein.

Mithieux G, Misery P, Magnan C, Pillot B, Gautier-Stein A, Bernard

C, Rajas F, Zitoun C.

Institut National de la Sante et de la Recherche Medicale, U449,

Lyon, F-69372, France. mithieux@...

Protein feeding is known to decrease hunger and subsequent food

intake in animals and humans. It has also been suggested that glucose

appearance into portal vein, as occurring during meal assimilation,

may induce comparable effects. Here, we connect these previous

observations by reporting that intestinal gluconeogenesis (i.e., de

novo synthesis of glucose) is induced during the postabsorptive time

(following food digestion) in rats specifically fed on

protein-enriched diet. This results in glucose release into portal

blood, counterbalancing the lowering of glycemia resulting from

intestinal glucose utilization. Comparable infusions into the portal

vein of control postabsorptive rats (fed on starch-enriched diet)

decrease food consumption and activate the hypothalamic nuclei

regulating food intake. Similar hypothalamic activation occurs on

protein feeding. All these effects are absent after denervation of the

portal vein. Thus, portal sensing of intestinal gluconeogenesis may be

a novel mechanism connecting the macronutrient composition of diet to

food intake.

PMID: 16271532