Effects of Protein Load Prior to the Main Meal of the Day: A Pilot Trial

Abstract

Background: High protein diets increase satiety and may decrease energy intake. Many overweight people overeat in the evening. We hypothesized that ingesting protein prior to the evening meal may limit successive calorie intake and generate weight loss. Aims: To explore whether protein pre-load before the evening meal will lead to weight loss compared to eating as usual. Methods: 129 adults with a Body Mass Index (BMI) ≥25 reporting eating large evening meals were randomized to either consume a 20 g protein bar 30 minutes before their evening meal daily for two weeks (Protein pre-loading (PP) arm) or not (No protein pre-loading (NP) arm). Hunger ratings were recorded, immediately prior to each evening meal. Participants returned at the end of weeks one and two to provide their weight and rating of hunger and any changes in evening food consumption since baseline. Results: There was no significant difference in weight loss between the study arms (Week1 PP: -0.13 kg, [SD=0.74] vs. NP: -0.06 kg, [SD=0.75], not significant (NS); Week2 PP: +0.06 kg, [SD=0.82] vs. NP: -0.005 kg, [SD=0.82], NS). Participants in the PP arm reported less hunger before evening meals than those in the NP arm (Week1: 4.97 [SD=0.94] vs. 3.72[SD=0.65], p < .0011; Week2: 4.95 [SD=0.94] vs. 3.69[SD=0.71], p < .001). They also reported eating less at their evening meals (Week1: 2.59[SD=0.53] vs. 2.11[SD=0.54], p < .001; Week2: 2.63[SD=0.49] vs. 2.10[SD=0.50], p < .001). Conclusion: Consuming 20 g of protein before the evening meal reduced hunger and self-reported food intake in the evening, but had no effect on weight.