The Look of Lifestyle after LOOK AHEAD
The results of the LOOK AHEAD trial were made public at the American Diabetes Association's 2013 conference. This trial found no benefit of intensive lifestyle therapy on 'hard' vascular outcomes during almost 10 years of follow up. However, this does not mean that lifestyle advice should no longer be advocated.
Firstly, the study demonstrated that both intensive lifestyle treatment, and the less intensive education that was given in the control group, will result in weight loss. For intensive lifestyle treatment the effect was about 9 kg while intensive treatment lasted, but as shown previously the effect waned after a few years. Interestingly, the more moderate advice in the control group was less efficacious in the beginning, but its effects seemed to last, with small weight losses accruing over 10 years. At endpoint, the intensive group was only 2,5 kg lighter than the control group.
Secondly, it was shown that the intensive lifestyle treatment and associated weight loss translated into modest differences compared to controls in HbA1c, from 0.6% in the beginning to 0.1% at endpoint. Similar improvements were seen in other cardiovascular risk factors, except for LDL (see below).
However, no effect on cardiovascular outcomes was found. Several explanations have been put forward for this phenomenon. Some suggested that the (slightly but significantly) higher use of statins and ACE-inhibition in the control group may have contributed. A more plausible explanation is however that the average weight loss and the ensuing improvements in cardiovascular risk factors was too modest to have any effect. Data in the literature suggest that the impact of diabetes on life-expectancy drops with higher age at diagnosis, as does the impact of lowering cholesterol and blood pressure. Since the participants were already 59 years at study entry with a Body Mass Index of 36 kg/m2, it may be that the small changes achieved over the 10 years of the study had too little impact in comparison with their prior decades of being overweight.
These results may seem disappointing, but as Hertzel Gerstein points out, beneficial effects of lifestyle improvements are biologically plausible and have been demonstrated for several other important outcomes such as the occurrence of sleep apnea. My personal conclusion would be that lifestyle improvement should be aimed for at a very early age to reap its full rewards, both in avoiding the level of overweight that LOOK AHEAD participants had and in their long term health outcomes.