Snacks consumed in a nonhungry state have poor satiating efficiency: influence of snack composition on substrate utilization and hunger

Background: Several epidemiologic studies suggest that snacking may play an etiologic role in obesity. Objective: We assessed the behavioral and metabolic consequences of a high-carbohydrate (HC) or high-protein (HP) snack consumed 215 min after lunch, thereby investigating ways that snacking in a nonhungry state could be involved in the etiology of obesity. Design: Eight lean young men attended 3 sessions (basal, HP snack, and HC snack) in a counterbalanced order with 2 wk between sessions. During all sessions, subjects were time-blinded while we measured the temporal pattern of plasma glucose, insulin, and fatty acid concentrations; hunger ratings; substrate oxidation; and energy expenditure from 215 min after the beginning of lunch until the spontaneous dinner request. Results: Compared with the basal (no snack) session, the HP snack delayed the spontaneous dinner request (by 38 +/- 16 min, P < 0.05) but the HC snack did not. Energy and macronutrient intakes at dinner were unaffected by both snacks. After the HP snack, plasma fatty acid concentrations were lower (P < 0.05), but glucose and insulin were unchanged compared with the basal session. After the HC snack, plasma glucose and insulin concentrations were higher and plasma fatty acid concentrations were lower than those in the basal session (P < 0.05 for both). Both snacks promoted carbohydrate utilization (P < 0.05), and the HC snack depressed fat oxidation (P < 0.05). Conclusion: This study showed that a snack consumed in a satiety state has poor satiating efficiency irrespective of its composition, which is evidence that snacking plays a role in obesity.