The metanalysis by Ma et al depends heavily on the LOOK AHEAD trial, which has a 55% weighting. Of the remaining 53 trials, 19 had the odd characteristic of having zero or one death in the intervention group. These 19 trials had 18 deaths in the controls and 9 with the intervention. A small change in the inclusion criteria for very-low-mortality studies could have easily led to a very different overall result. Except for the two largest studies, the dropout rate in all the studies exceeds the mortality by at least a factor 10. Many more patient outcomes are simply unknown relative to the number of documented deaths.
A crucial point found in the supplemental data tables is that a reduction in mortality only reached statistical significance when a "physical activity facility was provided". This metanalysis supports the conclusion that exercise is of critical importance for the longevity of the obese.
Competing interests:
No competing interests
27 November 2017
Paul R. Ernsberger
Associate Professor of Nutrition
Case Western Reserve Univ School of Medicine
Dept. of Nutrition, Case Western Reserve Univ. School of Medicine, 10900 Euclid Ave., Cleveland OH 44106 USA
Rapid Response:
One or none trials for mortality
The metanalysis by Ma et al depends heavily on the LOOK AHEAD trial, which has a 55% weighting. Of the remaining 53 trials, 19 had the odd characteristic of having zero or one death in the intervention group. These 19 trials had 18 deaths in the controls and 9 with the intervention. A small change in the inclusion criteria for very-low-mortality studies could have easily led to a very different overall result. Except for the two largest studies, the dropout rate in all the studies exceeds the mortality by at least a factor 10. Many more patient outcomes are simply unknown relative to the number of documented deaths.
A crucial point found in the supplemental data tables is that a reduction in mortality only reached statistical significance when a "physical activity facility was provided". This metanalysis supports the conclusion that exercise is of critical importance for the longevity of the obese.
Competing interests: No competing interests