However, we still don’t know exactly how strength training alters body fat. Part of the effect is due to the fact that muscle is metabolically active and burns calories, so adding muscle mass through weightlifting should increase resting energy expenditure and metabolic rate. For example, after six months of lifting weights, your muscles will burn more calories just because they’re bigger. But that doesn’t fully explain the effect, because adding muscle mass takes time and reps, while some of the metabolic effects of weight training on fat stores occur right after the workout.
So, immediately after fat cell-targeted resistance training, something is likely happening at the molecular level, a hypothesis recently explored by a group of scientists from the University of Kentucky at Lexington, the University of Nebraska-Lincoln, and other institutions. Researchers have studied muscle health for years, but have become increasingly interested in other tissues, particularly fat. Perhaps, they speculated, muscle and fat had a friendly exchange post-workout.
Over the past decade, the notion that cells and tissues communicate throughout our bodies has become widely accepted, although the complexity of these interactions remains a mystery. Sophisticated experiments show that after exercise, for example, muscles release a cascade of hormones and other proteins that enter the bloodstream, travel to various organs, and trigger biochemical reactions there, a process known as cell crosstalk.
Our tissue can also eject tiny bubbles called vesicles during crosstalk. Once thought to be microscopic garbage bags full of cellular debris, the vesicles are now known to contain healthy, active genetic material as well as other substances. When these substances are released into the bloodstream, they transfer this biological material from one tissue to another like tiny messages.
Interestingly, some experiments suggest that aerobic exercise causes muscles to release these vesicles, which carry a range of messages, but few studies had investigated whether resistance training could also lead to vesicle formation and the exchange of messages between muscle tissues.