Abstract
Objectives
Total energy intake is the product of portion size (PS), the energy content of an ingestive event, and ingestive frequency (IF), the number of ingestive events per unit time. An alteration in either portion size or ingestive frequency, that is not compensated by the other, must result in a change in energy intake and, if maintained over time, body weight. The primary objective of this meta-analysis was to assess the independent effects of PS and IF on dietary energy intake and body weight among healthy adults in randomized controlled trials.
Methods
8,614 articles (duplicates removed) published through 2018 with no date restriction were identified with PubMed, Web of Science, Cochrane, and CINAHL databases. The articles were divided among ten researchers and each article was screened for eligibility by two to three independent reviewers. Exclusion criteria included: populations <19 y and >65 y, unhealthy, assessment <24 h in duration, and controlled feeding trials. Studies investigating the effect of IF or PS on body weight were at least 4 weeks in duration. Eleven articles (IF = 3, PS = 8) met the inclusion criteria. There were not enough articles to assess the effect of PS on body weight.
Results
There was significant heterogeneity in the effect sizes among all comparisons (I2 = >50%). Consuming smaller portion sizes was associated with lower 24 h energy intake [–135 kcal (–249, –21), n = 15; WMD (95% CI), n = comparisons]. In contrast, IF was not associated with a difference in 24 h energy intake [–103 kcal (–230, 24), n = 5], but was positively related to body weight in trials ≥6 wk duration [0.40 kg (0.70, 0.11), n = 4].
Conclusions
Results from RCTs support that greater PS but not IF is associated with higher daily energy consumption. However, IF is positively associated with increased body weight over time.
Funding Sources
NA
Individual differences and moderating participant characteristics in the effect of reducing portion size on meal energy intake: Pooled analysis of three randomized controlled trials
