"This new research shows that the picture is more sophisticated than 'energy' alone: exercise has positive effects even when we are actively storing energy and gaining weight," James Betts of the University of Bath in England said in a statement.
The study involved 26 healthy young men who were asked to be generally inactive in their daily activities. Half of the group then exercised daily on a treadmill for 45 minutes. Everyone was asked to overeat: the non-exercising group increased their caloric intake by 50 percent, while the exercising group increased their food intake by 75 percent -- so everyone's net daily energy surplus was the same.
The study, published in The Journal of Physiology, found after one week, the groups had blood insulin measurements and biopsies of fat tissue taken, with striking results -- the non-exercising group showed a significant and unhealthy decline in their blood sugar control and their fat cells were over-expressing genes linked to unhealthy metabolic changes and were under-expressing genes involved in well-functioning metabolism.
However, the exercising group had stable blood sugar levels and their fat cells showed less "undesirable" genetic expression, the study said.
"A critical feature of our experiment is that we matched the energy surplus between groups -- so the exercise group consumed even more energy and were still better off at the end of the week," senior author Dr. Dylan Thompson said.