Participants were between the ages of 33 and 77 years old [mean: 53.5 (SD=8.4)]. Ninety-five percent were overweight or obese with a mean BMI of 35.8 kg/m2
(see ). Fifty-three percent were female, and 53% had a bachelor’s degree or higher education. Fifty-five percent were employed full time. Participants were predominantly white (85%) and married or living with partner (70%). Ninety percent (n=36) were taking medication for diabetes. Detailed diabetes medication use information at baseline was reported elsewhere [14
]. Briefly, the most common oral medication was metformin (73%), followed by glyburide (38%). Ten subjects (25%) used insulin in addition to oral hypoglycemic agents. The two groups resembled each other statistically in most baseline characteristics, except age where subjects in the ADA group were slightly younger.
Selected participants’ characteristics of the ADA and low-GI group at baseline (N=40), the Diabetic Educational Eating Plan (DEEP) study, Worcester, Massachusetts, 2005–2007.
presents HbA1c values as well as other physiological, dietary, and physical activity, and psychosocial variables over time. Three p-values are presented: 1) for time and group interaction, which is the test of treatment effect; 2) for time, which is the test whether the measure was changed over time; and 3) from t-test of the difference of two group means. These were obtained from mixed model fitting physiological, dietary intake, physical activity, or psychological variables as dependent variable, time measurement, treatment group, and interaction between time and group term as fixed effect, and subject as a random effect.
Physiological, dietary, and physical activity, and psychosocial variables over time by study group, the Diabetic Educational Eating Plan (DEEP) study, Worcester, Massachusetts, 2005–2007.
Mean HbA1c was significantly decreased during the study for both groups (p<0.001), especially between baseline and 6 months (8.1% to 7.4% for the ADA group, and 8.7% to 8.0% for the low-GI group), but were attenuated at 12 months. However, there is no treatment effect evident (p=0.88), and no difference between two groups on HbA1c at any time point. Results were similar after using baseline value carried forward for subjects with missing values.
Total cholesterol levels were significantly decreased (p=0.03) for both groups, but there was no significant difference between two groups. HDL and triglycerides were unchanged, nor was there a difference between the two groups. However, there was a difference in LDL cholesterol levels between two groups at 12 months (p=0.048). At 12 months, LDL cholesterol levels were significantly lower in low-GI group than the ADA group with LDL cholesterol levels decreasing by 17 mg/dl in the ADA group and increasing by 1.3 mg/dl in the low-GI group.
Diastolic blood pressure decreased significantly (p=0.01), and was significantly lower in the low-GI group compared to the ADA diet group (p=0.03) at 6 months. At 12 months, there was no significant difference in diastolic blood pressure between two groups, although both groups showed improvement from baseline values. Systolic blood pressure remained unchanged in both groups.
Although patients stated at baseline that they were not following a low or modified carbohydrate diet [14
], both groups consumed a very low percentage of calories from carbohydrates (37% in the ADA group versus 36% in the low-GI group at baseline), and very high percentage of calories from saturated fat (15% versus 14%, at baseline), which improved modestly in the low-GI group at 6 months (15.5% in the ADA group versus 12.7% in the low-GI group, p=0.03), and in both groups at 12 months (14.2% versus 13.2%, p=0.41).
Differences in dietary glycemic index between the two groups did not approach statistical significance until 12 months (80 in the ADA group versus 76 in the low-GI group, p=0.07). However, compared to the ADA group, GL was significantly lower in the low-GI group at 6 months (97 versus 141, p=0.02). Interestingly, at 12 months, total carbohydrate intake increased in the ADA group, but decreased in the low-GI group. Daily caloric intake dropped by 624 kcal in low-GI group at 6 months, and remained 325 kcal lower than baseline at 12 months. Caloric intake increased minimally in the ADA group. Depression and PAID scores slightly decreased within each group but did not reach statistical significance. These scores were also not significantly different between two groups at any time point.
presents summary data on diabetic medication change during the study. In the ADA group, two subjects decreased medication use and four subjects added medication or increased dose at 6 months. From 6 to 12 months, four participants added medication or increased dose. In the low-GI group, three subjects decreased medication use and one increased it at 6 months. While from 6 to 12 months, one participant decreased and two added medication or dose. Results from a ordinal logistic regression model for medication change showed that participants in the low-GI group had much lower likelihood of switching to a new drug or increasing dosage of diabetes medication (odds ratio (OR)=0.26, p=0.01). Also, higher BMI (OR=1.12, p=0.01), male gender (OR=2.83, p=0.08) and higher HbA1c (OR=1.53, p=0.02) predicted higher likelihood of switching to a new drug or increasing doses.
Average class attendance differed between groups, with an average attendance of 6.57 (SD=1.91) for ADA group and 4.50 (SD=1.90) for the low-GI group (p=0.002). Participants completed a questionnaire at the end of the study to assess the acceptability of the study. Both groups of participants liked the diet they were prescribed (100% in the GI versus 88% in the ADA group; p=0.49). Additionally, all participants in the low-GI group reported the intervention was helpful versus 77% in the ADA group (p=0.11). Thirty-five percent of ADA group versus 23% of low-GI group reported that it was difficult for them to maintain the new diet (p=0.69). All participants in the low-GI group and 71% of those in the ADA group reported enjoying eating unfamiliar foods (p=0.05). There were no diet-related adverse events reported in either group during the study.