title: The Effects of Increased Protein Intake on Fullness: A Meta-Analysis and Its Limitations.
abstract: BACKGROUND
  Higher protein intake has been implicated in weight management because of its appetitive properties. However, the effects of protein intake on appetitive sensations such as fullness have not been systematically assessed. Meta-analysis is a useful technique to evaluate evidence of an intervention's effect on testable outcomes, but it also has important limitations.
  
  
  OBJECTIVE
  The primary aim of this study was to synthesize the available evidence on the effect of protein intake on fullness using a quantitative meta-analysis and a secondary directional analysis using the vote-counting procedure. A tertiary aim was to address limitations of meta-analyses as they pertain to findings from this meta-analysis.
  
  
  METHODS
  We searched multiple databases for interventional studies that evaluated the effect of increased protein intake on fullness ratings. Inclusion criteria for both analyses were as follows: healthy human participants, preload studies that utilized intact dietary protein, delivery of protein load orally, and studies reporting fullness as an outcome. For the meta-analysis, an additional criterion was that the studies also needed to report 2- to 4-hour area under the curve value for fullness.
  
  
  RESULTS
  Five studies met all criteria for the meta-analysis. Twenty-eight studies met all criteria for the directional analysis. The meta-analysis indicated higher protein preloads have a greater effect on fullness than lower protein preloads (overall effect estimate: 2,435.74 mm.240 min, (95% CI 1,375.18 to 3,496.31 mm.240 min; P<0.0001). The directional analysis also revealed a positive effect on fullness with higher protein preloads (P<0.01). Many related scientifically rigorous studies were excluded from the analysis because analytical criteria required a narrowly focused research question.
  
  
  CONCLUSIONS
  The present analyses show that higher protein preloads increase fullness ratings more than lower protein preloads under tightly defined conditions. Extrapolation of findings to common conditions outside the specified criteria of this analysis must be made cautiously, as must speculation about the influence of fullness sensations on ingestive behavior, body weight, and various health outcomes.
authors.forename: Jaapna
authors.initials: J
authors.lastname: Dhillon
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Craig
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Leidy
authors.forename: Akua F
authors.initials: AF
authors.lastname: Amankwaah
authors.forename: Katherene
authors.initials: K
authors.lastname: Osei-Boadi Anguah
authors.forename: Ashley
authors.initials: A
authors.lastname: Jacobs
authors.forename: Blake L
authors.initials: BL
authors.lastname: Jones
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Jones
authors.forename: Chelsey L
authors.initials: CL
authors.lastname: Keeler
authors.forename: Christine E M
authors.initials: CE
authors.lastname: Keller
authors.forename: Megan A
authors.initials: MA
authors.lastname: McCrory
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Rivera
authors.forename: Maribeth
authors.initials: M
authors.lastname: Slebodnik
authors.forename: Richard D
authors.initials: RD
authors.lastname: Mattes
authors.forename: Robin M
authors.initials: RM
authors.lastname: Tucker
mesh_terms: D000328:Adult; D001066:Appetite / Q000187:drug effects*; D004044:Dietary Proteins / Q000494:pharmacology*; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D055815:Young Adult
chemical_list: D004044:Dietary Proteins
keywords: Appetitive sensations; Dietary protein; Fullness; Human preload studies; Meta-analysis limitations