JMIR Publications

ABSTRACT

Background:

A very low-carbohydrate (VLC) nutritional strategy may improve glycemic control and weight loss for adults with type 2 diabetes. However, it is uncertain what supplementary behavioral strategies might be able to improve outcomes using this nutritional strategy.

Objective:

We sought to compare the impact of adding three different supplementary behavioral strategies to a web-based VLC diet intervention.

Methods:

Participants were 112 overweight adults with type 2 diabetes (HbA1c ≥ 6.5%), taking no anti-glycemic medications or only metformin. They received a remotely-delivered 12-month VLC diet intervention. Participants were randomly assigned through a full-factorial 2x2x2 design to supplementary strategies: either daily or monthly dietary self-monitoring, either mindful eating training or not, and either positive affect skills training or not. To our knowledge, this is the first trial that has randomized participants to differing frequencies of dietary self-monitoring. Our goal was to screen for supplemental strategies that had at least a medium effect size (a Cohen’s d of 0.5).

Results:

Only one Cohen’s d point estimate reached 0.5: daily (vs. monthly) dietary self-monitoring had a worse impact on depressive symptoms (Cohen's d –0.47, 95% CI –0.02 to 0.95, p = 0.06). None of the strategies had a statistically significant effect on outcomes. For changes in our primary outcome, HbA1c, the daily (vs. monthly) dietary self-monitoring impact was 0.42% (95% CI –0.28% to 1.12%, Cohen's d 0.28, p = 0.24), for mindful eating it was –0.47% (95% CI –1.15% to 0.22%, Cohen's d –0.32, p = 0.18), and for positive affect it was 0.12% (95% CI –0.57% to 0.82%, Cohen's d 0.08, p = 0.72). Other results for daily (vs. monthly) dietary self-monitoring were mixed, suggesting an increase in weight (0.98%) and depressive symptoms (Cohen's d 0.47), less intervention satisfaction (Cohen's d –0.20), more classes viewed (2.05), and greater dietary adherence (Cohen's d 0.24). For mindful eating, results suggested a benefit for dietary adherence (Cohen's d 0.24) and intervention satisfaction (Cohen's d 0.30). For positive affect, results suggested a benefit for depressive symptoms (Cohen's d –0.32), number of classes viewed (2.04), dietary adherence (Cohen's d 0.16), and intervention satisfaction (Cohen's d 0.25). Overall, the VLC intervention led to statistically significantly improved glycemic control (–0.70%, 95% CI –1.04% to –0.35%, p<0.001), weight loss (–6.82%, 95% CI –8.57% to –5.08%, p<0.001), and depressive symptoms (Cohen's d –0.67, 95% CI –0.92 to –0.41, p<0.001). Thirty percent (25/83) of participants taking metformin at baseline reduced or discontinued their metformin.

Conclusions:

The addition of monthly (not daily) dietary self-monitoring, mindful eating, and positive affect skills training did not show definitive benefit but are worth testing further. Overall, our results support the use of a VLC diet intervention in adults with type 2 diabetes. Clinical Trial: ClinicalTrials.gov NCT03037528