Once type 2 diabetes mellitus is diagnosed, lifestyle management is a cornerstone of clinical care. This section reviews some of the evidence from large clinical trials that focus on lifestyle management in type 2 diabetes mellitus.
The Look AHEAD (Action for Health in Diabetes) study, conducted from 2001 to 2012, provided extensive longitudinal data on the effect of an intensive lifestyle management intervention, targeting weight reduction through caloric restriction and increased physical activity, on CVD rates (the primary outcome) and CVD risk factors among adults with type 2 diabetes mellitus. In this trial, 2,575 participants were randomized to a control group and 2,570 to an intervention that consisted of a weekly goal for physical activity of 50 min/week initially, increasing to 175min/week of moderately intense activity by week 26 (34).
The second component of the physical activity intervention included a focus on lifestyle activity (e.g., using the stairs instead of elevators, walking instead of riding), which is equally as effective as aerobic activity in leading to weight loss and improvement in CVD risk factors (35). Participants were provided a pedometer in the seventh week and instructed to increase their daily steps by 250 each week until they reached the goal of 10,000 a day. One-year results revealed that participants in the intensive lifestyle intervention achieved an average of 136.7 ± 110.4 min/week of physical activity; moreover, there was a significant association between the minutes of physical activity and weight loss at 12 months (36).
The primary results of Look AHEAD were published in 2013 (37). At 1 year, greater weight loss was observed in the intervention arm (8.6%) compared with the usual care arm (0.7%), which was attenuated but still sustained by the end of the study (6.0% versus 3.5%). In addition to weight loss, the patients in the intervention arm had improved physical fitness and HDL cholesterol (HDL-C) levels, had greater reductions in A1c and waist circumference, and required less medication for glucose, blood pressure, and lipid control. However, after a median follow-up of 9.6 years, the trial was stopped early because of futility:
There were 403 CVD events in the intervention arm compared with 418 CVD events in the usual care arm (hazard ratio [HR] 0.95 [95% CI 0.83–1.09]; P = 0.51). The reasons for this are not clear (38) but may be the result of decreased use of cardioprotective drugs, particularly statins, in the intervention group resulting from an improvement in risk factors with the lifestyle intervention. At a minimum, the study informs clinicians that increased physical activity and improvements in diet
In addition to physical activity, nutrition plays an important role in the treatment of type 2 diabetes mellitus and CVD risk prevention. Published recommendations for the treatment of people with diabetes mellitus assert the continued importance of diet, exercise, and education as a cornerstone of optimal diabetes mellitus treatment (4,40–43).
Current nutrition recommendations for individuals with type 2 diabetes mellitus center around a dietary pattern that emphasizes intake of fruits, vegetables, reduced saturated fat, and low-fat dairy products. The recommendations also consist of individualized modification of macro-nutrient intake to accommodate individual needs for the distribution of calories and carbohydrates over the course of the day. Eating patterns such as the Dietary Approaches to Stop Hypertension (DASH), Mediterranean, low-fat, or monitored carbohydrate diet are effective for controlling glycemia and lowering CVD risk factors (44). The Prevencion con Dieta Mediterranea (PREDIMED) trial was studying adapting a Mediterranean diet was an RCT looking atthe effect of a Mediterranean diet on CVD outcomes. Those patients randomized to the Mediterranean diet had a 30% reduced risk of CVD events (45). The prespecified diabetes mellitus subgroup demonstrated similar results, suggesting that a Mediterranean diet may promote CVD risk reduction in patients with diabetes mellitus.
Some data suggest that eating patterns with low glycemic index may be effective in achieving glycemic control (i.e., positive effects on postprandial blood glucose and insulin) and in lowering triglyceride levels (46–48), whereas other studies have shown no effect of low–glycemic index diets on triglycerides (49–51). The importance of the glycemic index needs further investigation.
Given that individuals with diabetes mellitus commonly have elevated triglycerides and reduced HDL-C levels, it is important to optimize nutrition-related practices, including moderate alcohol intake, substituting healthy fats (e.g., monounsaturated fatty acids, polyunsaturated fatty acids) for saturated and trans fats, limiting added sugars, engaging in regular physical activity, and losing excess weight. These changes can reduce triglycerides by 20% to 50% (52).