In addition, the comparison group took more heart-protective medications, particularly cholesterol-lowering statins, than the diet-and-exercise group. The comparison group had lower average LDL, or "bad" cholesterol throughout the study, which may mean that diet and exercise works about as well as drugs to protect the heart, not that lifestyle changes don't work at all.
Indeed, the rate of heart events two years into the study was lower than the researchers had anticipated, leading them to adjust the main goals of the study to include a more controversial measure of heart disease -- episodes of chest pain serious enough to cause hospitalization. Chest pain episodes were similar between the two groups, and may have diminished the study's ability to detect differences in more serious events like heart attacks and strokes.
One expert said stopping the study early may have had an impact on the results.
"My impression is that the trial was stopped too soon," said Dr. Frank Sacks, a professor of cardiovascular disease prevention at the Harvard School of Public Health. Sacks has seen the study, but was not involved in the research. "This can produce an underestimate of the effect of treatment."
The bottom line is that weight loss may not be enough to protect people with diabetes from heart disease, although it may have important benefits that go beyond the heart.
Study author Wing, however, said researchers found many other reasons doctors should continue to recommend diet and exercise for their patients. These findings were not part of the main outcomes of the NEJM study but were presented at the diabetes meeting.
Some of the most important improvements were related to the havoc diabetes can inflict on the smallest blood vessels in the body. These microvascular complications of diabetes can damage the kidneys, which often leads to dialysis, and damage to the retina of the eye, which can cause blindness.
"Intensive lifestyle intervention reduced the risk of chronic kidney disease by 31 percent," Wing said. "So we had a very, very marked effect on the development of high-risk chronic kidney disease. We also showed a benefit in terms of self-reported eye disease."
People who made lifestyle changes also had less serious depression, and they had better physical function than people in the comparison group. Because they needed fewer medications and went to the hospital less often than people in the control group, they saved money on their medical care -- about $600 a year, or $5,000 over the course of the study.
"That's pretty remarkable," said Sood at Lenox Hill Hospital, who will continue to recommend lifestyle changes that lead to weight loss, although her reasons for doing so will shift slightly. "Now we have data to show that quality of life, depression and other complications will improve."
To learn more about managing diabetes, head to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.
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