SystematicReviewandMeta-AnalysisontheEffect ofPortionSizeandIngestiveFrequencyonEnergy IntakeandBodyWeightamongAdultsin RandomizedControlledFeedingTrials

Abstract

Energyintakeistheproductofportionsize(PS)—theenergycontentofaningestiveevent—andingestivefrequency(IF)—thenumberofingestive eventsperunittime.AnuncompensatedalterationineitherPSorIFwouldresultinachangeinenergyintakeandbodyweightifmaintainedover time. The objective of this meta-analysis was to assess the independent effects of PS and IF on energy intake and body weight among healthy adultsinrandomizedcontrolledtrials(RCTs).Atotalof9708articleswereidentifiedinPubMed,WebofScience,Cochrane,andCINAHLdatabases. Thearticlesweredividedamong10researchers;eacharticlewasscreenedforeligibilityby2–3independentreviewers.Exclusioncriteriaincluded: populations <19yand >65y,unhealthypopulations(i.e.participantswithanacuteorchronicdisease),assessments <24hand <4wkinduration for trials investigating energy intake or body weight, respectively. Controlled feeding trials (i.e. fixed energy intake) that manipulated IF and PS in the same study intervention (IF/PS) were evaluated separately and for the body weight outcome only. Twenty-two studies (IF = 4, PS = 14, IF/PS = 4) met the inclusion criteria. There was an insufficient number of studies to assess the effect of IF, PS, or IF/PS on body weight. There was heterogeneity in the effect sizes among all comparisons (I2 ≥75%). Consuming larger portion sizes was associated with higher daily energy intake[295kcal(202,388),n=24;weightedmeandifferences(WMD)(95%CI),n=comparisons],andincreasedfrequencyofingestiveeventswas associated with higher energy intake [203 kcal (76, 330), n=10]. Results from RCTs support that larger PS and greater IF are both associated with higher energy consumption. However, there is insufficient information to determine chronic effects on body weight. This protocol was registered attheInternationalProspectiveRegisterofSystematicReviews(PROSPERO)asCRD42018104757