Appetite regulatory hormone responses to various dietary proteins differ by body mass index status despite similar reductions in ad libitum energy intake.

CONTEXT

Although dietary protein produces higher acute satiety relative to carbohydrate, the influence of protein source and body mass index (BMI) has not been clearly described.

OBJECTIVE

The objective of the study was to assess postprandial responses to different protein sources, compared with glucose, in males with normal and high BMI.

DESIGN

This was a randomized, crossover study of four preloads followed by blood sampling (+15, 30, 45, 60, 90, 120, 180 min) and buffet meal.

SETTING

The study was conducted at an outpatient clinic.

PARTICIPANTS

The study population included 72 men, with a BMI range 20.6-39.9 kg/m(2).

INTERVENTIONS

Interventions consisted of liquid preloads (1.1 MJ, 450 ml) containing 50 g whey, soy, gluten, or glucose.

MAIN OUTCOME MEASURES

Fasting and postprandial plasma glucose, insulin, ghrelin, glucagon-like peptide-1 (GLP-1) and cholecystokinin (n = 38), ad libitum energy intake, and appetite ratings were measured.

RESULTS

Energy intake was 10% lower after all protein preloads, compared with the glucose treatment (P < 0.05), independent of BMI status and protein type. All protein loads prolonged the postprandial suppression of ghrelin (P < 0.01) and elevation of GLP-1 (P < 0.01) and cholecystokinin (P < 0.05). Fasting GLP-1 concentrations [overweight, 17.5 +/- 1.3; lean, 14.7 +/- 0.1 pg/ml (5.2 +/- 0.4 and 4.4 +/- 0.1 pmol/liter, respectively); P < 0.001] and postprandial responses (P = 0.038) were higher in overweight subjects.

CONCLUSIONS

Whey, soy, and gluten similarly tend to reduce ad libitum food intake 3 h later in lean and overweight males relative to glucose. Postprandial ghrelin, GLP-1, insulin, and cholecystokinin may contribute to this higher satiety after protein consumption. GLP-1 concentrations are increased in overweight subjects, which may affect satiety responses in this group.