n a very closely controlled, year-long study with post-menopausal women—chosen as subjects because they are more stable, hormonally speaking—researchers divided the participants into an exercise intervention group and a control group.
All the subjects were carefully selected for specific features of their health and lifestyle. The subjects were all instructed not to change their dietary habits. The control group was assigned a moderate stretching regimen to use over the course of the study, and the intervention group was given a moderate intensity, 45-minute workout for five days a week, initially with supervision. There was detailed tracking, because the researchers were especially interested in identifying distinctions between genetic and environmental factors.
At the end of the study period, the researchers found a distinct variability in the amount of fat lost by some exercisers that could not be explained by their adherence levels.
The researchers looked to the genetic data, and indeed, there were two specific genes that stood out related to patterns of fat loss and exercise. Participants with certain combinations of those genes and their variants had significantly different fat loss outcomes.
The complex science at this level can be pretty confusing. Genes are named with different alpha-numeric codes and so are their variant alleles. If you're not careful, you can end up in some real alphabet soup just trying to talk about it, but basically two genes are involved here, the CYP19 and the COMT.
They found that having one CYP19 gene and its variants was not consistently associated with percentage fat, total fat, subcutaneous fat or intra-abdominal fat, that dangerous excess that gathers around our vital organs. But having two such genes correlated to a slightly larger decrease in body mass index, and a significantly larger decrease in total fat and percentage of body fat.
And having a particular genotype of the COMT gene, together with at least one copy of the CYP19 gene, also related to a significantly larger decrease in BMI, total fat and percentage of body fat. There were corresponding intermediate combinations and results that bore out the relationships.