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Diet Quality Improvement in Weight Loss Trials

Cheng, Jessica (2022) Diet Quality Improvement in Weight Loss Trials. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Diet quality, the healthfulness of the diet, has been shown to relate to both cardiometabolic risk factors and disease. As such, it may be a promising target in interventions among those with or at risk for chronic disease. However, research is needed to determine the ability of current behavioral interventions to affect diet quality.
This dissertation first systematically reviewed behavioral weight loss interventions which measured changes in diet quality in order to assess the methodological approaches taken by researchers. Articles were identified using PubMed, Ebscohost CINAHL, Ovid APA PsycINFO,, Scopus, and Web of Science (Manuscript 1). Data from the SMARTER randomized controlled trial (N=502) was also used to examine the effect of a mobile health intervention on diet quality improvements and the relationship between diet quality improvements and weight loss (Manuscript 2), and evaluated the relationship between perceived and calculated diet quality and diet quality improvement (Manuscript 3). Manuscript 2 used the Population Ratio Method and bootstrapping to compare confidence intervals between intervention and comparator groups and by weight loss status subgroups. Manuscript 3 used the concordance correlation coefficient and Bland-Altman plots.
The systematic review revealed few studies used preferred methods of diet quality calculation. Dietary improvements were small with little supporting evidence for incorporating specific behavioral strategies. In Manuscript 2, over follow-up, meaningful improvements in diet quality did not occur with the provision of feedback to dietary self-monitoring or with self-monitoring alone. However, improvements in diet quality were observed among those experiencing clinically meaningful weight loss. Manuscript 3 revealed misalignment between perceived and calculated diet quality, mostly due to better perceived diet quality. Misalignment was more pronounced when assessing change in diet quality.
Our analyses suggest more investigation and standardized reporting of whether meaningful diet quality changes are occurring in weight loss seeking adults undergoing behavioral treatment is needed. In SMARTER dietary improvements were not apparent overall, but were in adults with clinically relevant weight loss. Future studies should seek to improve on this success by identifying behavior change techniques supportive of diet quality improvement possibly including those targeted at misperception of dietary change.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Cheng, Jessicajec150@pitt.edujec1500000-0001-7869-4848
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee CoChairBurke, Loralbu100@pitt.edulbu100
Committee CoChairRockette-Wagner, BonnyBJR26@pitt.edubjr26
Committee MemberSereika, Susanssereika@pitt.edussereika
Committee MemberCostacou, TinaCostacouT@edc.pitt.eduCostacouT
Committee MemberKriska, AndreaKriskaA@edc.pitt.eduKriskaA
Committee MemberKlem, Mary Louklem@pitt.eduklem
Date: 1 September 2022
Date Type: Publication
Defense Date: 1 August 2022
Approval Date: 1 September 2022
Submission Date: 6 August 2022
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 180
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Epidemiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: diet; epidemiology; public health; obesity; nutrition; weight loss
Date Deposited: 01 Sep 2022 12:58
Last Modified: 01 Sep 2023 05:15


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