Protein Source Influences Acute Appetite and Satiety but Not Subsequent Food Intake in Healthy Adults.

BACKGROUND: Although current recommendations encourage plant-based dietary patterns, data is limited as to whether the equivalent substitution of animal-based protein-rich foods with plant-based versions impacts ingestive behavior. OBJECTIVES: To compare higher-protein preloads, varying in protein source, on appetite, satiety, and subsequent energy intake. METHODS: Thirty-two adults (age: 25 ± 1 y; body mass index (BMI) measured in kg/m2: 24.2 ± 0.5 kg/m2) randomly consumed 250 kcal, protein-preload beverages (24 g protein), varying in protein source [whey, soy, and pea protein isolates (WHEY, SOY, and PEA) or micellar casein (CAS)] each morning for 3 acclimation days/preload. On day 4, participants completed a 4-h clinical testing day in which the respective preload was consumed, followed by blood sampling and questionnaires every 30 min for appetite and satiety. In addition, an ad libitum lunch was provided 4-h postpreload. On day 5, participants consumed the respective preload at home, followed by an ad libitum breakfast 30 min afterward. For normally-distributed data, repeated-measures analysis of variance (ANOVA) or Friedman nonparametric test were utilized to compare the main effects of protein source on study outcomes. Post hoc pairwise comparisons using least-significant differences (LSD) were then performed. RESULTS: CAS (-3330 ± 690 mm∗240 min) and PEA (-2840 ± 930mm∗240 min) reduced 4-h appetite compared with SOY (-1440 ± 936 mm∗240 min; both, P < 0.05). WHEY was not different (-2290 ± 930 mm∗240 min). CAS (3520 ± 84 pg/mL∗240 min) and PEA (3860 ± 864 pg/mL∗240 min) increased 4-h peptide YY concentrations compared with SOY (2200 ± 869 pg/mL∗240 min; both, P < 0.05). WHEY was not different (3870 ± 932 pg/mL∗240 min). No differences in ad libitum energy intake were observed. CONCLUSIONS: CAS and PEA, but not WHEY, elicited greater acute changes in appetite and satiety compared with SOY in healthy adults, supporting that not all protein sources are equivalent. This trial is registered at clinicaltrials.gov (NCT03154606).

Examining the Direct and Indirect Effects of Postprandial Amino Acid Responses on Markers of Satiety following the Acute Consumption of Lean Beef-Rich Meals in Healthy Women with Overweight.

The consumption of protein-rich foods stimulates satiety more than other macronutrient-rich foods; however, the underlying mechanisms-of-action are not well-characterized. The objective of this study was to identify the direct and indirect effects of postprandial amino acid (AA) responses on satiety. Seventeen women (mean ± SEM, age: 33 ± 1 year; BMI: 27.8 ± 0.1 kg/m2) consumed a eucaloric, plant-based diet containing two servings of lean beef/day (i.e., 7.5 oz (207 g)) for 7 days. During day 6, the participants completed a 12 h controlled-feeding, clinical testing day including repeated satiety questionnaires and blood sampling to assess pre- and postprandial plasma AAs, PYY, and GLP-1. Regression and mediation analyses were completed to assess AA predictors and hormonal mediators. Total plasma AAs explained 41.1% of the variance in perceived daily fullness (p < 0.001), 61.0% in PYY (p < 0.001), and 66.1% in GLP-1 (p < 0.001) concentrations, respectively. Several individual AAs significantly predicted fluctuations in daily fullness, PYY, and GLP-1. In completing mediation analyses, the effect of plasma leucine on daily fullness was fully mediated by circulating PYY concentrations (indirect effect = B: 0.09 [Boot 95% CI: 0.032, 0.17]) as no leucine-fullness direct effect was observed. No other mediators were identified. Although a number of circulating AAs predict satiety, leucine was found to do so through changes in PYY concentrations in middle-aged women.

A Diet Containing Animal Source Protein as Fresh, Lean Beef Is More Well Liked and Promotes Healthier Eating Behavior Compared with Plant-Based Alternatives in Women with Overweight.

Background: Despite limited evidence from intervention trials, replacing animal-source protein-rich foods with plant alternatives continues to be recommended as part of a healthy dietary pattern. Objectives: The objective of this study was to examine whether a diet containing fresh, lean beef elicits greater satiety, reduces ad libitum food intake, and is more acceptable compared with a diet containing plant alternatives in women with overweight. Methods: Seventeen women with overweight (mean ± SEM, age: 33 ± 1 y; BMI: 27.8 ± 0.1 kg/m2) completed an acute, tightly controlled, crossover design study. Participants were provided with eucaloric, isonitrogenous diets (15% of daily intake as protein) containing either 2 servings/d of fresh lean beef (BEEF) or plant equivalents (PLANT) for 7 d/pattern. During day 6 of each pattern, the participants completed a 10-h controlled-feeding, clinical testing day, which included repeated appetite and satiety questionnaires and blood sampling to assess pre- and postprandial plasma peptide YY (PYY) and GLP-1 across the day. On day 7, the participants completed a free-living testing day in which they consumed their respective protein foods and were provided with additional carbohydrate- and fat-rich foods to consume, ad libitum, during each eating occasion. Energy and macronutrient composition were assessed. A 2- to 3-wk washout period occurred between patterns. Results: No differences in daily satiety were detected between patterns. During the ad libitum testing day, 24-h food intake was not different between patterns (BEEF: 2714 ± 219 compared with PLANT: 2859 ± 147 kcals/d), BEEF led to fewer carbohydrates consumed compared with PLANT (338 ± 34 compared with 370 ± 22 g/d, P < 0.05), especially as sugar (169 ± 73 g compared with 186 ± 57 g, P = 0.05). Furthermore, BEEF was more well liked (i.e., higher flavor, texture, and acceptability) compared with PLANT (all, P < 0.05). Conclusions: Although satiety was similar between patterns, the consumption of animal-source protein-rich foods, such as fresh and lean beef, was more well liked and resulted in voluntary reductions in total carbohydrate and sugar intake in middle-aged women with overweight during a single ad libitum testing day.This study was registered at clinicaltrials.gov as NCT02614729.