The inverse relation between bone and fat is also important for understanding why one youth might build more lean tissue (e.g., bone and muscle) while another youth accretes more fat. The key factor seems to be the amount of vigorous physical activity they engage in. It appears that the activity provides a mechanical stimulus to the mesenchymal stem cells that causes them to differentiate into lean rather than fat cells. This concept has important implications for the design of interventions to prevent child obesity. For more information, see Gutin (2013), Research Quarterly for Exercise and Sport, and Owens and Gutin (2014) Current Cardiovascular Risk Reports.