Two Diet Studies, Two Approaches to Finding Keys to Weight Loss, Reduced Risk Factors


Studies presented at the 2015 American Diabetes Association Scientific Sessions take different approaches on what percentage of carbohydrates should be part of a diet for persons with type 2 diabetes.

There’s no one way to lose weight and reduce risk factors for diabetes, and Saturday’s talks at the 75th Scientific Sessions of the American Diabetes Association (ADA) in Boston showed there’s no one way to study the process, either.

Back-to-back presentations at the session, “Concepts in Nutrition and Diabetes Prevention and Treatment,” offered 2 very different studies, each asking the question: which type of diet will not only help at-risk patients lose weight, but keep impaired glucose tolerance at bay?

Frankie B. Stentz, MS, PhD, associate professor of Medicine-Endocrinology at the University of Tennessee Health Science Center, presented results of an ADA-funded study that asked whether a diet high in carbohydrates or one high in protein would be best for obese patients who needed to lose weight and improve insulin sensitivity, as they had been diagnosed with prediabetes or impaired glucose tolerance.1

Dr Stentz noted the statistics: 80 million Americans have prediabetes, and “The rate of conversion to diabetes is 10% per year.” Diabetes can be held off with therapy, but lifestyle changes are twice as effective—if patients will do them.

The randomized controlled trial divided 18 obese patients into 2 groups: half would receive a high-protein (HP) diet, and half a high-carbohydrate (HC) diet. Patients’ prediabetes status was determined, with all receiving an oral glucose tolerance test. Patients were told to maintain current exercise levels. They received prepackaged meals and were weighed each week, given a daily meal plan, and asked to follow a checklist to monitor compliance.

The HP diet was 30% protein, 30% fat, and 40% carbohydrates; the HC diet was 15% protein, 30% fat, and 55% carbohydrates. All meals were balanced with fruits and vegetables, she said. The study period was 6 months.

Both groups lost weight, with greater overall weight loss in the HC group. But on nearly every other health indicator, the HP diet produced better results (averages):

· Glycated hemoglobin (A1C). The HP group decreased 5.99% to 5.53%; the HC group decreased 5.9% to 5.69%.

· Homeostatic IR. HP group 4.69 to 1.58; HC group 4.62 to 3.15.

· Conversion rate. The HP group had a 100% conversion rate to normal glucose tolerance, compared with 44.4% for the HC group.

· Lean body mass. HP has an increase of 2.8%, and the HC group had a decrease of 2.1%.

· Fat body mass. HP had a decrease of 2.5%, and the HC group had a decrease of 3.5%.

“Our results suggest that lean body mass preservation may be more than important than total weight loss in the conversion of impaired glucose tolerance to normal glucose tolerance, possibly due to the high insulin sensitivity of muscle cells,” the researchers found.

Macrobiotic Diet Study. If carbohydrates proved less beneficial in the ADA-funded study, they were the centerpiece of the diet studied by researchers from the MADIAB Group.

“There is no one-size-fits-all dietary plan for people with type 2 diabetes,” said Yeganeh M. Khazrai, MD, who presented results on behalf of the group, based at University Campus Bio-Medico, in Rome, Italy. Their work presumes that a vegan-style diet—whole grains, seasonal vegetables, no animal protein or fat—would be beneficial for patients with T2DM. Unlike the other diet presented, this one is 70% carbohydrates, 18% fat, and 12% protein, with 30 to 35g of fiber content per 1000 kcal.

An initial study involved putting 2 groups of 25 patients each—the study group and a control—in a hotel for 21 days, where they Dr Khazrai said they were “obviously happy; they were looked after very well,” despite strict monitoring. Results reported Saturday were a follow-up after 6 months.2 “We decided to evaluate whether these benefits could be kept in the long run,” she said.

Participants in the macrobiotic diet had already seen benefits after the initial 21-day study period. Notably, only 17 of the original 25 participants in the vegan group remained by the end of the follow-up period. Results (averages) the start and end of the 6-month follow-up are:

· A1C. For the vegan group, 6.4% to 5.9% at both the 3-month and 6-month marks; for the control group, 6.6% to 6.2% at 3 months and 6.3% at 6 months.

· Weight loss. Major weight loss in the vegan group, to an average of 77.1 kg vs 85.6 kg in the control group, was maintained up to 6 months.

· Lipid profile. Both groups maintained their lipid profile in the recommended range for age and gender at the 6-month follow-up.

The authors concluded, “Beyond the type of diet, a close follow-up and a continuous reinforced diet program helps maintaining metabolic control in type 2 diabetic patients on the long-term.”

One questioner asked whether it was easy to get participants to embrace a vegan-style diet in Italy, and whether that was reflected in the drop-out rate. Dr Khazrai noted the fact that 17 others stayed with the diet, and that 2 who left, "were not from Rome."


1. Kitabchi AE, Brewer A, Wan J, Sands C, Stentz FB. Remission of impaired glucose tolerance to normal glucose tolerance in obese adult with high protein vs high carbohydrate diet. Diabetes. 2015; 64(suppl1) abstract 90-OR.

2. Soare A. A 6-months study of two different diets in type 2 diabetes (the follow-up MADIAB trial). Diabetes. 2015; 64(suppl1) abstract 91-OR.

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