Isocaloric-restricted Mediterranean Diet and Chinese Diets High or Low in Plants in Adults With Prediabetes

Abstract

Context: Calorie restriction plus dietary advice is suggested as a preventive strategy for individuals with obesity and prediabetes; however, optimal diet is still debatable. We aimed to compare the effects of Mediterranean diet (MD) and Chinese diets high or low in plants on body weight and glucose homeostasis among high-risk Chinese.

Subjects and methods: In this parallel-arm randomized controlled trial, 253 Chinese adults aged 25 to 60 years with a body mass index ≥ 24.0 kg/m2 and fasting blood glucose ≥ 5.6 mmol/L were randomly assigned to 3 isocaloric-restricted diets: MD (n = 84), a traditional Jiangnan diet high in plants (TJD, n = 85), or a control diet low in plants (CD, n = 84). During the 6-month trial, a 5-weekday full-feeding regimen was followed, along with mobile app-based monitoring. Abdominal fat measurement (magnetic resonance imaging), oral glucose tolerance test (OGTT), and continuous glucose monitoring (CGM) were conducted at baseline and 3 and 6 months.

Results: With a 25% calorie restriction for 6 months, weight deduction was 5.72 kg (95% confidence interval, 5.03-6.40) for MD, 5.05 kg (4.38-5.73) for TJD, and 5.38 kg (4.70-6.06) for CD (Ptime < 0.0001). No between-group differences were found for fasting glucose, insulin, and the Matsuda index from OGTT. Notably, CD had significantly longer time below range (glucose < 3.9 mmol/L) than MD (0.81% [0.21-1.40], P = 0.024) and marginally longer time than TJD (0.56% [-0.03 to 1.15], P = 0.065), as measured by CGM.

Conclusions: With the 6-month isocaloric-restricted feeding, TJD and MD achieved comparable weight deduction and improved glucose homeostasis, whereas CD showed a higher risk for hypoglycemia.

Trial registration: ClinicalTrials.gov NCT03856762.

Keywords: Mediterranean diet; continuous glucose monitoring; oral glucose tolerance test; overweight; plant-based diet; prediabetes.

Figure 1.

Trial flow diagram.

Figure 2.

Changes in body weight monitored by scales at home during the intervention. The within-group changes from baseline are presented as estimated marginal means (Mediterranean diet [MD], n = 84; traditional Jiangnan diet [TJD], n = 85; control diet [CD], n = 84). Error bars show 95% CI. ↓ represent rebounds at weekends or on holidays. P group × time was examined by mixed-effects linear models with unstructured variance structure, which was adjusted for age, sex, baseline fasting glucose, physical activity, and baseline body weight.

Figure 3.

Changes in whole-day glucose homeostasis and nocturnal glucose fluctuation from CGM. The within-group changes from baseline are expressed as estimated marginal means (Mediterranean diet [MD], n = 78; traditional Jiangnan diet [TJD], n = 73; control diet [CD], n = 75). Error bars show 95% CI. (A) Mean glucose. (B) TBR was calculated and displayed in square-root form. (C) TAR was calculated and displayed in square-root form. (D) Nighttime SD. P group × time on variables were examined by mixed-effects linear models with unstructured variance structure, which adjusted for age, sex, baseline BMI, baseline fasting glucose, physical activity, and baseline values. P MD vs TJD, P MD vs CD, P TJD vs CD were P values for the comparison between Mediterranean diet and traditional Jiangnan diet, Mediterranean diet and control diet, traditional Jiangnan diet and control diet at 6 months with Bonferroni adjustment. Abbreviations: AUC, area under the curve hourly; CGM, continuous glucose monitoring; TAR, time above range (>10 mmol/L); TBR, time below range (<3.9 mmol/L).

Figure 4.

Compliance, step record and appetitive measurements during intervention. The values are presented as observed means (Mediterranean diet [MD], n = 84; traditional Jiangnan diet [TJD], n = 85; control diet [CD], n = 84). Error bars indicate 95% CI. P group × time on variables were examined by mixed-effects linear models with unstructured variance structure, which adjusted for age, sex, baseline BMI, baseline fasting glucose, physical activity, and baseline values. (A) The rate of compliance. (B) Step record. (C) Fullness. (D) Hunger. (E) Prospective consumption. (F) Eating capacity.