Blood (plasma) insulin levels dropped during the two higher intensity sessions, likely due to the utilization of blood sugar (glucose) for energy, whereas the lower intensity session didn’t affect blood sugar levels, possibly due to the light load and short duration. Plasma epinephrine (adrenalin) only increased during the final, high-intensity session. This may be a reflection of low blood sugar (due to prolonged fasting and exercise) and the need to recruit more muscle fibers to generate the force demanded by the researchers.12

    This study was interesting because it looked at an issue that had been ignored for several decades. If a “spot reducing” effect of exercise is present, it would offer bodybuilders the hope that they might train their way to shredded glutes and striated quads. Indeed, the study demonstrated that the two identified components relating to local fat loss— increased blood flow and increased release of stored fat— are present over the exercising quadriceps, but not consistently.

    The researchers discussed the various ways that the body might induce greater fat loss and blood flow in the fat tissue overlying exercising muscle. The need to increase heat loss is one factor possibly accounting for the increase in blood flow, as was the increase in sympathetic tone (adrenalin) needed to release stored energy and recruit muscle fibers at the highest intensity. Another component recently covered in MD, was the release of the lipolytic cytokine interleukin-6 (IL-6) from the contracting muscle.13 IL-6 is a signaling chemical that participates in inflammation and the immune system’s response to viruses and bacteria, but also plays a role in reducing body fat.14