Curr Diab Rep (2013) 13:860–868 DOI 10.1007/s11892-013-0423-7
PSYCHOSOCIAL ASPECTS (KK HOOD, SECTION EDITOR)
Impact of Behavioral Interventions in the Management of Adults with Type 2 Diabetes Mellitus Daniel J. Cox & Ann Gill Taylor & Elizabeth S. Dunning & Mary C. Winston & Ingrid L. Luk Van & Anthony McCall & Harsimran Singh & William S. Yancy Jr.
Published online: 27 September 2013 # Springer Science+Business Media New York 2013
Abstract Research on the role of behavior change as an efficacious intervention for adults with type 2 diabetes is evolving. Searching PubMed and Ovid Medline, we identified and reviewed primarily randomized controlled trials from 2010 to 2013 of adults managing type 2 diabetes without insulin. All studies are evaluated in terms of the rigor of their design and their impact on glycosylated hemoglobin. The most efficacious interventions appear to be low-carbohydrate/glycemic load diets, combined aerobic and resistance training, and selfmonitoring of blood glucose, which educates patients about the impact of their food selections and physical activity on their blood glucose. Keywords Lifestyle intervention . Type 2 diabetes . Dietary intervention . Glycemic load . Glycemic index . Carbohydrate . Exercise . Physical activity . Aerobic exercise . Resistance training . Self-monitoring of blood glucose . Glycosylated hemoglobin . Blood glucose . Postprandial blood glucose . D. J. Cox (*) : I. L. Luk Van Behavioral Medicine Center, University of Virginia School of Medicine, 1300 JPA, UVA Hospital West, Barringer IV, Charlottesville, VA 22908, USA e-mail:
[email protected]
Insulin sensitivity . Glycemic control . Cardiovascular risk profile . Adults . Jadad Scale . Hyperglycemia
Introduction Recommendations on the role of “lifestyle modification” (LM) as the initial treatment of type 2 diabetes (T2D) are unclear and appear to have changed. In a joint consensus statement from the American Diabetes Association (ADA) and the European Association for the Study of Diabetes in 2009 [1], the recommended initial treatment at the time of diagnosis was to routinely include metformin, if tolerated, in addition to LM. This recommended initial treatment was modified in 2012 [2]; LM is now recommended as the sole initial treatment when the diagnostic glycosylated hemoglobin (HbA1c) is 7.5 % or lower. However, few studies have investigated the efficacy of LM as the initial treatment. Moreover, it
A. McCall Endocrinology and Metabolism, University of Virginia School of Medicine, 450 Ray C. Hunt Drive, Charlottesville, VA 22903, USA e-mail:
[email protected]
I. L. Luk Van e-mail:
[email protected] A. G. Taylor : E. S. Dunning : M. C. Winston University of Virginia School of Nursing, 202 Jeanette Lancaster Way, Charlottesville, VA 22903, USA A. G. Taylor e-mail:
[email protected] E. S. Dunning e-mail:
[email protected] M. C. Winston e-mail:
[email protected]
H. Singh Division of Behavioral Health and Technology, University of Virginia School of Medicine, 310 Old Ivy Way, Ste. 102, Charlottesville, VA 22903, USA e-mail:
[email protected]
W. S. Yancy Jr. Durham Veterans Affairs Medical Center, Duke University School of Medicine, 508 Fulton St., Durham, NC 27705, USA e-mail:
[email protected]
Curr Diab Rep (2013) 13:860–868
has not always been specified how to best implement diet modification, weight loss, and increased moderate physical activity with precise delineation of the most useful parameters. This review clarifies the HbA1c-lowering efficacy of three basic aspects of LM: (1) food selection to minimize postprandial blood glucose (BG), (2) physical activity to both promote immediate utilization of BG and reduce insulin resistance, and (3) self-monitoring of BG (SMBG) to inform individuals of the impact their food choices and activity levels have on their immediate BG levels. This article reviews primarily randomized, controlled trials (RCTs) from 2010 to 2013 incorporating adults with T2D. As a common metric for comparison, all RCTs are given a modified Jadad score [3], a validated measure of study design quality that ranges from 0 (low ) to 5 (high), and group mean reduction of HbA1c is reported. For the reader’s convenience, discussed studies are summarized in Table 1.
Dietary Intervention Prior to the advent of exogenous insulin therapy, manipulation of the diet was the primary strategy for lowering BG and improving survival. At that time, a diet with a very low carbohydrate content and glycemic load (GL) was typically prescribed and resulted in noticeable health improvements [4]. Since then, various dietary approaches have been studied and/ or recommended for patients with diabetes. This section reviews 15 published articles assessing dietary approaches to glycemic management in patients with T2D. Dietary approaches and/or individual dietary components may be effective for controlling BG, as well as various specific risk factors for cardiovascular disease (CVD), but there is no particular approach with conclusive data. Of the dietary approaches included in an updated literature review by the ADA [5], lower carbohydrate diets led most frequently to benefits in regard to glycemic control, whereas multiple approaches (e.g., lower carbohydrate, Mediterranean diet, low glycemic index [GI], higher protein content) led to benefits in CVD risk factors. Another systematic review [6] included RCTs of comprehensive dietary approaches in patients with T2D lasting at least 6 months and published before August 2011. The reviewers performed a meta-analysis, finding that low-carbohydrate, low-GI, Mediterranean, and high-protein diets all led to improvements in glycemia, as compared with a control diet (typically, a higher carbohydrate, lower fat diet). The weighted mean differences for the low-carbohydrate and Mediterranean diets actually may have been underestimated because the results from one of the included studies [7] were misclassified. The low-carbohydrate, low-GI, and Mediterranean diets also led to improved HDL cholesterol levels. Because the four diet approaches mentioned appear to hold the
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most promise for diabetes management, the rest of the section will review recent trials assessing these approaches. Low-Carbohydrate Diet Low-carbohydrate diets typically have demonstrated improvements in glycemic parameters while, in some trials, simultaneously resulting in the need for lower antiglycemic medication doses. Beneficial effects on body measurements and CVD risk factors also have been observed in these studies. Large-scale trials with clinical event outcomes, however, have not yet been performed. Two RCTs [8, 9] published from 2010 to 2013 showed improvements in glycemic control from a low-carbohydrate diet. In a low-intensity intervention [8], HbA1c decreased significantly from baseline to 6 months from 7.5 %±2.8 % to 7.0 %±2.9 % in patients following a low-carbohydrate diet. Simultaneously, insulin dose also decreased significantly in these participants. However, these effects did not hold at 12 months and were not statistically different from the comparison high-carbohydrate diet, in which neither HbA1c nor insulin dose changed significantly at any time point. HDL-C increased over time within both diet groups, with similar changes between groups. Weight loss also was similar between groups (approximately 4 kg at 6 months). In a three-arm RCT [9], 117 patients with T2D and a stable medication regimen were randomized to replace some of their typical carbohydrate intake with nuts (low carbohydrates), a whole wheat muffin, or half servings of each for 3 months. The group with a full serving of nuts daily lowered their carbohydrate intake below 40 % of daily energy intake and experienced a 0.21 % decrease in HbA1c, which was a significantly greater decrease than either of the other two arms. LDL-C also decreased more in the full-nut condition than in the full-muffin condition. In a nonrandomized study [10], 363 participants, 102 of whom had T2D, chose between either a low-calorie diet (LCD) or a low carbohydrate ketogenic diet (LCKD). In the T2D patients, despite reductions in antiglycemic medication use in the LCKD arm only, HbA1c decreased more with the LCKD (7.8 % to 6.3 %) than with the LCD (8.3 % to 7.6 %). The LCKD participants with T2D also experienced improvements in weight (−12.0 % vs. −7.0 %), serum triglycerides, and HDL-C. In a single-arm trial [11], 52 patients with T2D (not on insulin therapy) followed a moderately low-carbohydrate (35 %–40 % of daily energy intake) diet for 6 months. Weight decreased modestly (~2 kg), whereas HbA1c decreased substantially (8.4 % to 6.5 % in men, p
