Less Medication, Better Glycemic Control Seen in Low Saturated Fat Diet for Type 2 Diabetes

For individuals with type 2 diabetes mellitus (T2DM), a low-carbohydrate, low-saturated fat diet in combination with exercise resulted in superior glycemic control with less medication use than did a higher carbohydrate diet. These results, drawn from a year-long randomized parallel study presented November 7 at Obesity Week 2014 in Boston, MA, were presented by Jeannie Tay of the Commonwealth Scientific and Industrial Research Organization in Adelaide, Australia.

Tay and colleagues examined a very low carbohydrate, low saturated fat diet (LC) in comparison with a higher carbohydrate diet emphasizing unrefined carbohydrates (HC), combining both with a structured exercise program. Energy supplied by both arms was individually calculated to achieve modest caloric restriction of about 500 Kcal/day. In the LC arm, the macronutrient distribution supplied 14% of energy from carbohydrates, 28% from protein, and 58% from fat, with less than 10% saturated fat. For the HC group, 53% of energy was from carbohydrates, 17% from protein, and 30% from fat, also with less than 10% saturated fat.

The study was open to individuals with T2D and obesity; participants (n=115, 66 males), whose mean age was 58, had a baseline mean BMI of 34.6 kg and HbA1c of 7.3. Participants were randomized in block fashion to LC or HC arms.

Participants received intensive dietary counseling, meeting with a dietitian every 2 weeks for 12 weeks and monthly thereafter. At these meetings, participants were given food samples of key foods appropriate to their intervention arm in an amount to meet approximately 30% of energy needs; after 12 weeks, this was alternated monthly with a $50 food voucher. Both arms also participated in hour-long thrice-weekly supervised exercise training of moderate intensity with both an aerobic and a strength component.

In order to assess adherence to diet and exercise protocols, participants completed weighed food records, and plasma ketones and urea/creatinine ratios were obtained every four weeks. Participants also wore wrist accelerometers for a seven day period during the study.

The study was completed by 78 of the 115 enrollees (68%), with no difference in completion between the two diet types. Both groups lost a significant and similar amount of weight (LC, -9.8 kg; HC, -10.1 kg). Fat mass reduction was also similar, at 7.9 kg for the LC and 8.6 kg for the HC group. Blood pressure and fasting glucose were also significantly lowered in both groups; no diet effect was seen.

Though both diet types produced a significant reduction in HbA1c of 1%, the LC dieters also achieved a three-fold reduction in diabetes medication use compared with the HC group. The LC diet also seemed to have an attenuating effect on diurnal blood glucose variation as measured by continuous blood glucose monitoring for a 48 hour period; blood glucose excursions were twice as variable in the HC as in the LC group.

Tay noted that these results show that though both diet types produce weight loss and improvement in HbA1c for individuals with T2DM, the LC diet produced greater triglyceride reduction and a greater increase in high density lipoprotein (HDL) levels when compared to the HC diet group. However, the LC group maintained similar levels of low density lipoprotein (LDL) when compared with the HC arm after a full year of intervention. This, Tay said, may be attributable to the low saturated fat content of the LC diet — a distinguishing feature of this LC intervention compared to other studies (which have sometimes resulted in LDL increases).