Diet, exercise or therapy?
Almost 60% of the world’s adults could be either obese or overweight by 2030 according to the projections of Kelly et al. (2008). It is well known that obesity is associated with several diseases, which are widely prevalent. The reason we are so interested in reducing obesity and studying weight loss is because it affects such large numbers of the population. This time we focus on how effective are different ways of approaching weight loss relative to each other.
More specifically we look at how diet alone or exercise alone compares to programs which include both plus a behavioural intervention. We’ll call the latter combined programs.
The information we’ll present here is based on the review Johns et al. (2014) which includes 8 studies. People participating in this study had BMI’s greater than or equal to 25, meaning they were either overweight or obese and were adults. In total they were 1,022. The values used were recorded at the end of the 3 month, 6 month, 12 month and 18 month period.
Weight lost in the immediate future was more or less the same for diet only and combined programs. In contrast that was not the case between physical activity alone and combined programs, where the latter were more effective. In the long term combined programs seem to lead to more weight lost than either diet alone or physical activity alone programs. Two more interesting facts were one that a change in diet leads not only to lower food intake but in more exercise as well, and two that increased exercise may reduce food intake too.
As a general conclusion we may observe that combined programs are more effective for someone who is in it for the long haul. Another observation is that diet is more important than exercise, at least in the beginning of an effort to lose weight. However, it looks like that exercise is crucial for one to keep losing weight even after the first few months and for maintaining it well after that. Psychological support is also important for the long term effectiveness of a weight loss program, highlighting what we do wrong and motivating us.
Johns DJ, Hartmann-Boyce J, Jebb SA, Aveyard P, Diet or exercise interventions vs combined behavioral weight management programs: a systematic review and meta-analysis of direct comparisons, J Acad Nutr Diet, 2014; 114:1557-1568.
Kelly T, Yang W, Chen CS, Reynolds K, He J, Global burden of obesity in 2005 and projections to 2030, International Journal of Obesity, 2008; 32, 1431-1437.