Impact of individual and environmental factors on dietary or lifestyle interventions to prevent type 2 diabetes development: a systematic review

Abstract

Background: The variability in the effectiveness of type 2 diabetes (T2D) preventive interventions highlights the potential to identify the factors that determine treatment responses and those that would benefit the most from a given intervention. We conducted a systematic review to synthesize the evidence to support whether sociodemographic, clinical, behavioral, and molecular factors modify the efficacy of dietary or lifestyle interventions to prevent T2D.

Methods: We searched MEDLINE, Embase, and Cochrane databases for studies reporting on the effect of a lifestyle, dietary pattern, or dietary supplement interventions on the incidence of T2D and reporting the results stratified by any effect modifier. We extracted relevant statistical findings and qualitatively synthesized the evidence for each modifier based on the direction of findings reported in available studies. We used the Diabetes Canada Clinical Practice Scale to assess the certainty of the evidence for a given effect modifier.

Results: The 81 publications that met our criteria for inclusion are from 33 unique trials. The evidence is low to very low to attribute variability in intervention effectiveness to individual characteristics such as age, sex, BMI, race/ethnicity, socioeconomic status, baseline behavioral factors, or genetic predisposition.

Conclusions: We report evidence, albeit low certainty, that those with poorer health status, particularly those with prediabetes at baseline, tend to benefit more from T2D prevention strategies compared to healthier counterparts. Our synthesis highlights the need for purposefully designed clinical trials to inform whether individual factors influence the success of T2D prevention strategies.

Fig. 1. PRISMA flow diagram.

Stepwise screening stages adapted for selecting the studies of interest using Covidence software. Screening at all stages was done by two independent reviewers, and a third reviewer resolved conflicts.

Fig. 2. Potential effect modifiers of lifestyle, diet, and diet supplements intervention on the incidence of T2D.

General overview of potential effect modifiers of lifestyle (a), dietary (b), and supplement (c) interventions on the incidence of type 2 diabetes. The Y axes indicate potential effect modifiers, and the X axes illustrate the total number of trial participants included in the studies investigating each modifier. The proportion of gray or white in each bar indicates the number of trial participants included in the studies where there was (gray) or was not (white) an effect by the effect modifier. Caution is warranted because whether an effect modifier did (or did not) have an effect is based on statistical significance from the publication’s summary statistics. It is improbable that the effect modifier strictly did (or did not) have an effect on every participant included in that publication. The number of trials and trial participants are plotted because some trials (e.g., DPP) had multiple studies published using the same participants, so that the participant number would be heavily skewed. There was no instance where the same trial had multiple published studies evaluating the same effect modifier showing different results (e.g., there was no difference between sexes on the PREDIMED trial’s effect on T2D incidence in their primary vs. subgroup studies/publications). The number at the end of each bar represents the number of trials for each potential effect modifier. *indicates an exception for genetics because the effect modifiers (SNPs or GRS) were all uniquely distinct but are presented together under the categories of “SNP” or “GRS” here.