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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #203637
Title: The effects of the dietary glycemic load on type 2 diabetes risk factors during weight loss

Author
item PITTAS, ANASTASSIOS - TNEMC ENDOCRINOLOGY
item Roberts, Susan
item DAS, SAI KRUPA - HNRCA AT TUFTS
item GILHOOLY, CHERYL - HNRCA AT TUFTS
item Saltzman, Edward
item GOLDEN, JULIE - HNRCA AT TUFTS
item STARK, PAUL - TNEMC ENDOCRINOLOGY
item Greenberg, Andrew

Submitted to: Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2006
Publication Date: 12/1/2006
Citation: Pittas, A., Roberts, S., Das, S., Gilhooly, C.A., Saltzman, E., Golden, J., Stark, P.C., Greenberg, A.S. 2006. The effects of the dietary glycemic load on type 2 diabetes risk factors during weight loss. Obesity (Silver Spring, Md.). 14(12):2200-9.

Interpretive Summary: Questions remain whether integrating the glycemic load (GL) concept in energy-restricted nutritional interventions will decrease risk for glucose intolerance and type 2 diabetes (t2DM) above and beyond any benefits seen by weight loss (17). The controversy persists, at least in part, because of lack of data from long-term intervention studies with controlled diets that have focused on GL as a nutritional intervention modality for prevention of glucose intolerance. As part of a larger investigation of the effect of calorie restriction in healthy overweight adults, we used data from the first 6 months of a longer trial when all food was provided, to test the hypothesis that two calorie-restricted diets that differ in GL have differential effects on major risk factors for development of t2DM, such as glucose-insulin dynamics and plasma C-reactive protein (CRP) concentration. In healthy overweight adults provided with food for 6 months, dietary GL did not appear to have benefits in glucose-insulin dynamics above that associated with weight loss. However, declines in CRP were substantially greater in the LG group, suggesting an important potential for lower GL diets to reduce the risk of t2DM through decreased systemic inflammation. The improvement in systemic inflammation seen in the low GL diet, may help explain the decreased risk of t2DM in individuals consuming a low GL diets seen in observational studies.

Technical Abstract: Objective. To compare the effects of two calorie-restricted diets that differ in glycemic load (GL) on glucose-insulin dynamics and systemic inflammation. Design. Randomized controlled feeding trial. Setting and Participants. Thirty-four healthy overweight adults aged 24-42 years with normal fasting glucose. Interventions. Thirty percent calorie-restricted diets with high (HG) or low (LG) glycemic load. Participants received all meals as outpatients for 6-months. Main Outcome Measures. Changes in glucose-insulin dynamics during fasting and after a 75-gram oral glucose load (OGTT), and C-reactive protein (CRP) from 0 to 6 months. A subgroup of participants (n=25) also underwent a Frequently Sampled Intravenous Glucose Tolerance Test (FSIVGTT) at 0 and 6 months. Results. Compared to baseline, fasting insulin, homeostasis model assessment-insulin resistance (HOMA-R), post-load insulin at 30 min, and incremental AUC-insulin during OGTT were significantly lower in both groups at 6 months (p range 0.01 to 0.05), but after adjusting for baseline values and weight change there were no differences between the two groups in changes over time in any parameter. The mean percent change between baseline and 6 months in insulin sensitivity [Si] by FSIVGTT was +26% in HG and +24% in LG group (p=0.83); 1st phase acute insulin release [AIRg] was -20% in HG and -21% in the LG group (p=0.77). More participants in the LG diet had a decline in serum C-reactive protein (14 out of 16) compared to those in the HG diet (7 out of 16) (p<0.05). Conclusions. In healthy overweight adults provided with food for 6 months, dietary GL did not appear to have benefits in glucose-insulin dynamics above that associated with weight loss. However, declines in CRP were substantially greater in the LG group, suggesting an important potential for lower GL diets to reduce the risk of type 2 diabetes through decreased systemic inflammation.