Despair in the NEJM. “Cardiovascular Effects of Intensive Lifestyle Intervention in Type 2 Diabetes“:
Weight loss is recommended for overweight or obese patients with type 2 diabetes on the basis of short-term studies, but long-term effects on cardiovascular disease remain unknown. We examined whether an intensive lifestyle intervention for weight loss would decrease cardiovascular morbidity and mortality among such patients.
In 16 study centers in the United States, we randomly assigned 5145 overweight or obese patients with type 2 diabetes to participate in an intensive lifestyle intervention that promoted weight loss through decreased caloric intake and increased physical activity (intervention group) or to receive diabetes support and education (control group). The primary outcome was a composite of death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for angina during a maximum follow-up of 13.5 years.
The rationale for this study was simple. The researchers wanted to see if patients with type 2 diabetes who lost weight might have better cardiovascular outcomes. They got more than 5000 such people and randomized them to a normal education group, or a diet and physical activity program. The main outcome of interest was reduced death from cardiovascular causes for up to 13.5 years.
The good news is that people in the intervention group lost more weight than those in the control group (8.6% vs 0.7% at one year, and 6% vs 3.5% at study end). Furthermore, those in the intervention group saw greater improvements in glycated hemoglobin, fitness, and risk factors. The bad news is that after almost a decade, there was just no difference in the real outcome of interest. The number of deaths from cardiovascular causes was just no different.
They actually stopped the trial early, once a “futility analysis” showed it just wasn’t going to work, even if they waited a few more years.
Now some will point to the “failure” of this study as proof that weight reduction doesn’t save lives. That’s true, if the only outcome you care about is death. But here in the real world, we care about many more things, which are also important. People who lose weight can see improvement in lots of domains, including depression, physical functioning, sleep apnea, and plain old quality of life.
By focusing on the big outcomes while ignoring many of the smaller interim gains, we can lose sight of what matters. I’m not saying the study authors did this. I fear that some interpreting the results might, however.