Efficacy of lifestyle interventions in patients with type 2 diabetes: A systematic review and meta-analysis

Highlights

• Diet modification and physical activity are used for the evaluation of type 2 diabetes.

• DIET intervention shows improvement in HbA1c, blood pressure, and the quality of life.

• Nutrition had a significant impact on the QOL by reducing cardiovascular risk.

Abstract

Background

The current meta-analysis evaluated the outcomes of various lifestyle interventions, including diet modifications (DIET), physical activity (PA), and patient education (EDU) in reducing the risk of cardiovascular disease in patients with type 2 diabetes.

Methods

Randomized clinical trials comparing lifestyle intervention with “usual care” (control) in type 2 diabetes patients were hand-searched from medical databases by two independent reviewers using the terms “diabetes, cardiovascular risk, lifestyle, health education, dietary, exercise/physical activities, and behavior intervention”.

Results

Of the 235 studies identified, 17 were chosen for the meta-analysis. The average age of patients ranged from 50–67.3 years. Results reveal no significant difference between the groups, with respect to BMI, while PA and DIET yielded a greater reduction in HbA1c. Significant reduction in both systolic and diastolic pressures in the DIET group, and diastolic pressure in the PA group, was observed. HDL-c in the DIET group was significantly higher than the control group, while no change in LDL-c levels, was seen in all three intervention subtypes. There was no difference between the EDU vs. the control group in terms of HbA1c, blood pressure or HDL-c and LDL-c.

Conclusion

DIET intervention showed an improvement in HbA1c, systolic/diastolic blood pressure and HDL-c, with an exception of LDL-c and BMI, suggesting that nutritional intervention had a significant impact on the quality of life by reducing the cardiovascular risk in type 2 diabetes patients.

Introduction

The global increase in the prevalence of diabetes seen in recent years has been attributed mostly to obesity, poor diet, and lack of physical activity. The World Health Organization projects diabetes as the 7th leading cause of death and estimates that there will be 366 million adults with diabetes in 2030 [1], [2]. Of which, 90% of people will have type 2 diabetes, resulting from the body's ineffective use of insulin [3] and poor glycemic control. Reduced metabolic control of glucose can in turn increase the risk of cardiovascular diseases (CVD). The common cardiovascular risk factors associated with diabetes include, increased body weight, glycemia, serum lipids, and blood pressure [4].

Improvement of glycemic control and reduction of cardiovascular risk factors through diet and exercise has long been advocated [5], [6]. However, with the introduction of many new oral hypoglycemic agents, such as the glucagon-like peptide-1 receptor (GLP-1R) agonist and dipeptidyl peptidase-4 (DPP-4) inhibitors, in addition to the conventional metformin mono-therapy and increased use of insulin, the nutritional control of diabetes seemed to have lost its relevance [7], [8], [9]. Furthermore, the expectation of strict adherence to dietary control, exercise regimen and other lifestyle changes is not as realistic as the drug treatment in many patients. Besides, the evidence for dietary modifications in glycemic control, though compelling, is often based on short term studies, mostly one year or less [10], [11]. Clinical trials with a longer follow-up period are often necessary to confirm the positive impact of lifestyle changes in reducing the CVD in type 2 diabetes patients.

Recently, the Look AHEAD study examined the effects of an intensive lifestyle intervention (with diet modification and physical activity) over a period of four years in a large cohort of overweight and obese individuals with type 2 diabetes [12]. The results indicate that patients who underwent intensive lifestyle intervention as opposed to diabetes support and education (control), had better glycemic control, blood pressure, high density lipoprotein-cholesterol (HDL-C) and triglyceride levels, thus lowering their cardiovascular disease risk. Though, the maximum benefits were seen at one year, the intervention group had greater improvements over the control group even at 4 years.

In contrast, a long term behavioral intervention program, providing a regular, personalized exercise prescription did not improve glycemic control in sedentary, insulin treated type 2 patients during a 2 year intervention period [13], indicating that a more strictly supervised exercise training with personal coaching may be required to maximize the adherence and to increase the physical activity status. Similarly, a randomized clinical trial to determine the effect of case management in the control of diabetes in type 2 diabetes patients did not yield any significant difference between the case management and the control groups [14]. There was no difference in the mean HbA1c level, or low density lipoprotein-cholesterol (LDL-C) or blood pressure (BP) among the groups, suggesting cautious use of resources on personalized interventions and case management in the treatment of type 2 diabetes.

Though exercise has been shown to have a positive effect on cardiovascular health, the effect of exercise on BP reduction in type 2 diabetic patients is inconsistent. Recent findings suggest that though there was no reduction in BP, a modest reduction in the HbA1c levels (0.2%) was observed in the exercise group [15], further substantiating the protective effect of exercise on glycemic control. Reports elsewhere further corroborate the effectiveness of exercise intervention strategies in promoting physical activity and improving HbA1c and cardiovascular risk profile [16]. The above study also revealed that counseling alone, though effective in achieving the recommended level of physical activity (PA), was unsuccessful in minimizing the cardiovascular risk, suggesting the need for a larger volume of PA in high-risk patients. Conversely, Kirk et al. [17] reported that counseling improved glycemic control as well as the status of cardiovascular risk factors in type 2 diabetic patients. In reports elsewhere, regular drug-counseling through pharmacist care program significantly reduced the various CVD risk factors, including stroke [18].

The aforementioned studies along with various other reports indicate that structured reinforcement with diabetes health education, counseling, physical activity programs, and nutritional control can control the risk of CVD in patients with type 2 diabetes [19], [20], [21], [22], [23], [24], [25], [26]. The aim of the present meta-analysis is to compare the outcomes of intensive exercise, dietary regimens, and comprehensive lifestyle interventions and its significance on clinical markers of cardiovascular disease in patients with type 2 diabetes.