Look AHEAD – A Valid Study Design?
The Look AHEAD Research Group studied the effect of weight loss on cardiovascular morbidity and mortality in diabetic patients. Over 5000 patients were randomized to intensive lifestyle intervention (decreased caloric intake and increased physical activity) or a diabetes education and support group. The intervention group lost about 6% of their body weight vs 3.5% in the control group by the time of the study end. Suprisingly, there was no difference between the two groups in cardiovascular mortality.
Sounds like a huge practice-changing finding, challenging everything we know about lifestyle interventions in obesity … until you find in the methods section that they screened every participant with a treadmill cardiac stress test, and excluded anyone with an abnormal result. Then, decided to call the trial futile after only 9 years of follow up.
Of course there was no difference in the incidence of CV events! If you remove everyone from the trial who is at high risk you are excluding the very people who your intervention may have benefited.
Read the full article here.