The effect of peanut and grain bar preloads on postmeal satiety, glycemia, and weight loss in healthy individuals: an acute and a chronic randomized intervention trial

Abstract

Background: Peanut consumption favorably influences satiety. This study examined the acute effect of peanut versus grain bar preloads on postmeal satiety and glycemia in healthy adults and the long-term effect of these meal preloads on body mass in healthy overweight adults.

Methods: In the acute crossover trial (n = 15; 28.4 ± 2.9 y; 23.1 ± 0.9 kg/m2), the preload (isoenergetic peanut or grain bar with water, or water alone) was followed after 60 min with ingestion of a standardized glycemic test meal. Satiety and blood glucose were assessed immediately prior to the preload and to the test meal, and for two hours postmeal at 30-min intervals. In the parallel-arm, randomized trial (n = 44; 40.5 ± 1.6 y, 31.8 ± 0.9 kg/m2), the peanut or grain bar preload was consumed one hour prior to the evening meal for eight weeks. Body mass was measured at 2-week intervals, and secondary endpoints included blood hemoglobin A1c and energy intake as assessed by 3-d diet records collected at pre-trial and trial weeks 1 and 8.

Results: Satiety was elevated in the postprandial period following grain bar ingestion in comparison to peanut or water ingestion (p = 0.001, repeated-measures ANOVA). Blood glucose was elevated one hour after ingestion of the grain bar as compared to the peanut or water treatments; yet, total glycemia did not vary between treatments in the two hour postprandial period. In the 8-week trial, body mass was reduced for the grain bar versus peanut groups after eight weeks (-1.3 ± 0.4 kg versus -0.2 ± 0.3 kg, p = 0.033, analysis of covariance). Energy intake was reduced by 458 kcal/d in the first week of the trial for the grain bar group as compared to the peanut group (p = 0.118). Hemoglobin A1c changed significantly between groups during the trial (-0.25 ± 0.07% and -0.18 ± 0.12% for the grain bar and peanut groups respectively, p = 0.001).

Conclusions: Compared to an isoenergetic peanut preload, consumption of a grain bar preload one hour prior to a standardized meal significantly raised postmeal satiety. Moreover, consumption of the grain bar prior to the evening meal was associated with significant weight loss over time suggesting that glycemic carbohydrate ingestion prior to meals may be a weight management strategy.

Figure 1

Perceived satiety during the acute trial (mean ± SE; n = 15). At time 0 the test meal was consumed, which was exactly one hour after ingestion of the control treatment (1 c water) or the peanut or grain bar treatments, each with 1 c water. Satiety curves differed significantly (repeated measures ANOVA, time x group interaction; p = 0.002). The area-under-curve for 0–120 minutes differed by treatment (see inset; p = 0.003). * satiety for control treatment significantly less than that for peanut or grain bar (p < 0.05). ** satiety for grain bar significantly greater than that for peanut or grain bar (p < 0.05). ‡ satiety for grain bar significantly greater than that for peanut (p = 0.023).

Figure 2

Incremental serum glucose for the acute trial (mean ± SE; n = 15). At time 0 the test meal was consumed, which was exactly one hour after ingestion of the control treatment (1 c water) or the peanut or grain bar treatment, each with 1 c water. Incremental plasma glucose curves differed significantly (repeated measures ANOVA, time x group interaction; p = 0.023). The incremental area-under-curve for 0–120 minutes did not differ by treatment (see inset; p = 0.901). * glucose excursion for grain bar significantly greater than that for peanut or control (p < 0.001). ** glucose excursion for control significantly greater than that for peanut or grain bar (p < 0.05).

Figure 3

Incremental plasma insulin concentrations for the acute trial (mean ± SE; n = 13). At time 0 the test meal was consumed, which was exactly one hour after ingestion of the control treatment (1 c water) or the peanut or grain bar treatment, each with 1 c water. Incremental plasma insulin did not differ between groups (repeated measures ANOVA, time x group interaction; p = 0.268).

Figure 4

Change from baseline for body weight during the 8-week trial and the subsequent 8-week follow-up period. Data for trial weeks 2–8 represent participants who completed the 8-week trial (n = 23 and 21 for peanut and grain bar group respectively). Follow-up data represent 23/19 and 21/18 participants for peanut/grain bar groups at weeks 12 and 16 respectively. 8LOCF data represents the intention-to-treat LOCF method at week 8 (n = 26 and 24 for peanut and grain bar groups). Asterisks indicate significant difference between groups (p < 0.05).