SAN DIEGO – An intensive diet intervention soon after diagnosis improved glycemic control, but the addition of physical activity provided no additional benefit in a randomized, controlled trial of 593 adults with recently diagnosed type 2 diabetes.
"These findings suggest that intervention at this early stage should focus on improving diet, since the additional cost of training health care workers to promote activity might not be justified," Dr. Robert C. Andrews of the University of Bristol (England) and his associates said.
Previous meta-analyses of exercise and diet studies have demonstrated significant reductions in hemoglobin A1c levels (HbA1c) of 0.5 to 0.8 percentage points with aerobic and resistance exercise and by dietary intervention. However, most of the studies included were of short duration, involved small numbers of patients, and rarely included newly diagnosed type 2 diabetes patients, the investigators said.
The Early Activity in Diabetes (Early ACTID) trial randomized patients, aged 30-80 years, who had been diagnosed with type 2 diabetes in the prior 5-8 months to one of three groups: A control group of 99 patients who received usual care, including standard dietary and exercise advice after randomization and at the end of the study; an intervention group of 248 patients who received only an intensive dietary intervention aimed at achieving a 5%-10% body weight loss; another intervention group of 246 patients who received the same dietary intervention, along with a physical activity intervention.
Patients in both intervention groups saw dieticians at baseline (for 1 hour) and at 3, 6, and 9 months (for 30 minutes), along with reinforcement by nurses during 15-minute visits about once every 6 weeks. Patients in the intensive diet and physical activity group received the same dietary intervention as did those in the intensive diet group. Additionally, they were asked to do at least 30 minutes of brisk walking at least 5 days per week. Activity targets were gradually increased over 5 weeks and then were maintained for the rest of the study.
At baseline, glycemic control was good in most patients across all groups, with 68% having HbA1c below 7%, which is within the expected range in newly diagnosed patients, Dr. Andrews and his associates noted (Lancet 2011 [doi:10.1016/S0140-6736(11)60442-X]).
The primary end point was improvement in HbA1c and blood pressure at 6 months.
The intention-to-treat comparison showed no differences between the intensive diet intervention and the intensive diet intervention plus activity for any primary outcomes. Mean HbA1c concentrations were significantly lower at 6 and 12 months in patients who received either study intervention than in those who received usual care. At 12 months, HbA1c values were 6.8% for the usual care group, 6.6% for diet alone group, and 6.7% for the diet and activity group. Systolic blood pressures were nearly identical for the three groups, 133 mm Hg, 132 mm Hg, and 133 mm Hg, respectively, with no significant differences from baseline in any of the groups.
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Participants in the diet and exercise intervention group walked briskly for 30 minutes five times a week.
Both intervention groups had significantly greater improvements than did the control group on secondary end points such as weight, reduction in waist and hip circumference, bioimpedance, and insulin resistance. However, the difference between the intervention groups was not significant.
Improvements were also seen in both study intervention groups at 6 months in concentrations of HDL cholesterol and triglycerides, more so in the intensive diet and activity group than in the intensive diet alone group, although these values were similar between the groups at 12 months.
Use of diabetes medications did not differ between the three groups at 6 months, but participants in the usual care group were more likely to be taking a diabetes medication at 12 months. Use of antihypertensive or antihyperlipidemic drugs did not differ at 6 or 12 months among the three groups.
The intensive diet intervention plus activity seemed to yield better results for HbA1c concentration, body mass index, and insulin resistance in patients who had high baseline values than for those with low baseline values. For systolic blood pressure and, to a lesser degree, diastolic blood pressure, the diet and exercise intervention became less effective with increasing age at baseline, they said.
The exercise intervention may not have been effective because the activity undertaken might have been of insufficient intensity or been the incorrect type. The timing of the intervention may have been too early in the disease process to show additional response, as suggested by the fact that the diet plus exercise intervention worked best in patients who had high baseline HbA1c concentrations, insulin resistance, and BMI values.