Consuming Beef vs. Soy Protein Has Little Effect on Appetite, Satiety, and Food Intake in Healthy Adults

Abstract

Background: Although protein-rich plant foods have recently been touted as an equivalent to animal products, limited data exist regarding the effects of animal vs. plant proteins on appetite, satiety, and subsequent food intake.

Objective: The objective was to determine whether a high-protein beef lunch alters the appetitive, hormonal, and neural signals controlling food intake regulation vs. a macronutrient and fiber-matched (MF) or serving size-matched (SS) soy lunch in healthy adults.

Methods: A randomized, double-blind, crossover design study was completed in 21 adults (aged 23 ± 1 y; body mass index: 23.8 ± 0.6 kg/m²; mean ± SEM) to compare 400-kcal MF and SS lunches varying in protein quality. The MF lunches contained 24-g beef protein or 24-g soy protein, whereas the SS lunches contained 1 serving of beef (24-g protein/1-g fiber) or soy (14-g protein/5-g fiber). Pre- and postlunch appetite questionnaires and blood sampling were completed over an 8-h period until dinner was voluntarily requested. In addition, pre- and postlunch functional MRI brain scans were completed to assess neural activation in response to food stimuli.

Results: On average, dinner was requested at ∼250 ± 20 min postlunch with no differences between beef vs. soy within the MF and SS conditions. Furthermore, no differences in hunger, fullness, peptide YY, or glucagon-like peptide-1 responses were observed after the beef vs. soy lunches within the MF and SS conditions. The SS beef meal led to reductions in anterior cingulate activation (-22 ± 6%) vs. soy (+7 ± 9%; P < 0.01) and greater reductions in insular activation (-30 ± 6%) vs. SS soy (-7 ± 10%; P < 0.01). The participants consumed ∼945 ± 78 kcal after the MF meals and 910 ± 74 kcal after the SS meals with no differences between beef vs. soy.

Conclusions: When comparing 2 high-quality protein sources, such as beef and soy, the type of protein consumed within a mixed meal elicited very little effect on appetite, satiety, and food intake in healthy adults.

Trial registration: ClinicalTrials.gov NCT02285907.

Keywords: beef; fMRI; high-protein diets; satiety; soy.

© 2015 American Society for Nutrition.

Figures

FIGURE 1

Changes in hunger (A), fullness (B), and plasma GLP-1 (C) and PYY (D) concentrations relative to the consumption of the macronutrient- and fiber-matched BEEF and SOY lunch meals in 21 healthy adults. The diamond represents time when lunch was provided. Values are means ± SEMs,n = 21. GLP-1, glucagon-like peptide-1; PYY, peptide YY.

FIGURE 2

Changes in hunger (A), fullness (B), GLP-1 plasma concentrations (C), and PYY plasma concentrations (D) relative to the consumption of the serving size–matched BEEF and SOY lunch meals in 21 healthy adults. The diamond represents time when lunch was provided. Values are means ± SEMs,n = 21. GLP-1, glucagon-like peptide-1; PYY, peptide YY.

FIGURE 3

Brain activation contrast maps after the serving size–matched BEEF vs. SOY lunch meals in 21 healthy adults. Panel A depicts the fMRI brain contrast maps in which the change in neural responses after the SOY meal is greater than the BEEF meal (P < 0.01), whereas panel B represents the percent signal change after the BEEF vs. SOY meal. Values are means ± SEMs,n = 21. *Different from SOY,P < 0.05.