Here were each group's goals:
The vegan diet (~10% of energy from fat, 15% protein, and 75% carbohydrate) consisted of vegetables, fruits, grains, and legumes. Participants were asked to avoid animal products and added fats and to favor low–glycemic index foods, such as beans and green vegetables. Portion sizes, energy intake, and carbohydrate intake were unrestricted.
The conventional diabetes diet (15–20% protein, <7% saturated fat, 60–70% carbohydrate and monounsaturated fats, and cholesterol ≤200 mg/day) was individualized, based on body weight and plasma lipid concentrations.
Here's what participants ate over the course of 22 weeks (which did not quite meet their goals). Click to enlarge:*
Vegan Diet: Caloric intake 1425 kcal/day, Cholesterol 24 mg/day
Diabetes Diet: Caloric intake 1392 kcal/day, Cholesterol 189 mg/day
What happens when people with diabetes eat a high-carb diet ... consuming 70% of their calories as carbohydrates?
Here's how each group fared (all of the following reached levels of significance):
Among participants whose diabetes medications remained unchanged:
A1C fell 1.23 points in the vegan group
A1C fell 0.38 points in the ADA group
(A1C is short for HbA1c, a measure of blood glucose over the last 3 months)
Reduction in diabetes medications:
43% (21 of 49) of the vegan group
26% (13 of 50) of the ADA group
Body weight decreased:
6.5 kg [14.3 lbs] in the vegan group
3.1 kg [6.8 lbs] in the ADA group
Among those who did not change lipid-lowering medications:
LDL cholesterol fell 21.2% in the vegan group
LDL cholesterol fell 10.7% in the ADA group
Reductions in urinary albumin:2
15.9 mg/24h in the vegan group
10.9 mg/24 h in the ADA group
In sum, those on the high-carb vegan diet had lower blood sugars (and so could reduce their meds more), lower LDL cholesterol, improved kidney function and over double the weight loss. There were also significantly greater reductions in BMI, waist circumference, and total cholesterol in the vegan group compared to the ADA group. There was no significant difference in exercise between groups, so these changes weren't because vegans were overtly spending more calories. ("Overtly" is key, since, as previously discussed, some diets lead to greater expenditure of calories from digestion and thermogenesis.)
Gary Taubes in his book, Good Calories, Bad Calories said, "Carbohydrates make us fat and ultimately cause obesity. The fewer carbohydrates we consume, the leaner we will be." He also said, "Refined carbohydrates, starches, and sugars are the dietary cause of coronary heart disease and diabetes." This study did not support his claims.
This is noteworthy ... Participants in the vegan group were allowed unrestricted consumption. They could eat as many calories and as much carbohydrate as they wanted, as long as they didn't eat from certain food groups. Participants in the conventional diet group had to limit their caloric intake, count calories, and control portion sizes. Even with unrestricted food intake and a higher calorie consumption, the vegan group lost more than twice as much weight.
2 People with diabetes suffer microvascular complications involving the kidneys that allow passage of protein into urine. The lower the amount of the protein albumin that leaks into the urine, the healthier the kidneys.
Charts: Bix. Data from study.