News Review From Harvard Medical School -- Weight Loss Disappoints in Study of Diabetics
A study of diabetics has been stopped early because an intensive diet and exercise program did not reduce their risk of heart attack or stroke. Adults with type 2 diabetes have twice the risk of these problems as other adults. The study included 5,145 overweight or obese adults with type 2 diabetes. They were randomly divided into 2 groups. One group followed a strict diet. People were limited to 1,200 to 1,800 calories a day. They also did 175 minutes a week of moderate exercise. The other group just received general diabetes education and support. People in the first group lost about 10% of their weight at first. They kept off about 5% for at least 4 years. Other research has shown that a 5% weight loss can reduce factors that affect heart and stroke risk. People in the second group lost about 1% of their weight. After 11 years, U.S. government sponsors decided to stop the study. That's because the 2 groups had similar rates of heart attack, stroke, hospital stays for angina (chest pain) and heart-related death. Study results have not yet been published. The New York Times and MedPage Today wrote about it October 20.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Studies that don't show what we expect can be just as important as ones that confirm what we expect. This "negative" study is a great example. Before this study began, many people would have asked "Why do it?" It seemed obvious that cutting calories and increasing exercise would help overweight people with type 2 diabetes.
It's surely what I would have expected. But in fact no benefits were seen from such a program compared with people who received usual care. Because of this, the study was stopped early. The researchers were expecting to see fewer:
- Heart attacks
- Hospital trips because of angina (chest pain)
- Deaths caused by heart, stroke or other blood vessel diseases
But the two groups had similar rates of these adverse health events.
Does this mean that diet and exercise are not important in the treatment of type 2 diabetes? Wrong. This is not the take-home message.
In fact, there are some very good reasons to possibly explain why researchers saw no difference in these outcomes. For example, it may be that fewer heart attacks and strokes won't show up for 10 years or more. Was the study stopped too early?
Or perhaps the types of foods allowed in the calorie restricted diet weren't the best choices. The study began before the big push to eat more fruits and vegetables, whole grains and fish. And maybe a goal of only 175 minutes of exercise per week was too low. With a different diet and more intense physical activity, would the results have been different?
What if there was no difference because people in the two groups didn't take the same medicines? What if people who just got their usual care took different and/or higher doses of the kinds of medicines we know decrease the risk of heart attacks, strokes and kidney damage in people with diabetes?
If indeed there was a big difference between the medicines used, it could be a very important finding. The conclusion might be that combining diet and exercise with slightly higher doses of these medicines might have a huge impact.
We will need to see the published results to help answer some of these questions. But we get a hint that there were differences in medicines between the two groups. The people in the usual care group actually had lower LDL (bad) cholesterol levels than those in the weight loss and exercise group. This suggests that people in the usual care group were taking higher doses of statins. These are the drugs used most often to lower LDL cholesterol. Lower LDL levels decrease the risk of heart attack and stroke.
What Changes Can I Make Now?
No matter how much you weigh, diabetes increases your risk of developing and dying from heart disease. A recent study found twice the risk of dying for people who had a normal body weight when diagnosed with type 2 diabetes, compared with people who were diagnosed when overweight or obese.
As with this new study, many people were surprised by the findings. The reasons for this so-called paradox are not clear. But the two studies do suggest that maintaining a healthy weight is just one part of diabetes treatment.
Because diabetes puts you at increased risk of heart disease, you need to aggressively manage other factors that increase heart risk. The same risk factors that lead to more heart attacks and strokes in all of us have an even worse impact on people with diabetes.
Here's what you can do to reduce your risk of heart disease if you have diabetes, or even pre-diabetes.
- Don't smoke.
- Keep blood pressure as low as you can. Work with your doctor to find the best drugs for you. Your goal should be a blood pressure reading of less than 130/80. There are lots of drug choices. I usually start with an angiotensin enzyme inhibitor (ACE inhibitor) or angiotensin receptor blocker (ARB). Even if your blood pressure is normal, you should take an ACE inhibitor or ARB if you have protein in your urine.
- Aggressively lower your LDL cholesterol. This usually means taking a statin. Your LDL cholesterol target should be less than 100 milligrams per deciliter (mg/dL). But many doctors set a goal of less than 70 mg/dL.
- Consider taking a baby aspirin daily if you have one or more other heart disease risk factors besides diabetes. However, discuss this with your doctor first.
What Can I Expect Looking to the Future?
If the current trend continues, as many as 1 in 3 Americans will have type 2 diabetes by 2050. So every well-done study to help us learn how we can stem the tide is important. This includes "negative" studies, such as this one. I look forward to the published results. They likely will offer more clues about why diet and exercise did not have the expected positive impact.