What is the mechanism that links large muscle mass to kidney damage?
LH: The kidneys are the main filtering organ for the body and are composed of small filtering units called glomeruli. You’re born with a certain number of glomeruli, and they can’t regenerate or increase in number. When you gain an extreme amount of muscle mass, each of those individual filters must work a little harder to help the body dispose of waste products. If the glomeruli become overworked, they can become damaged to the extent that they scar. That pattern of injury is called focal segmental glomerulosclerosis. JB: If extreme muscle mass may constitute a risk factor for the development of FSGS in bodybuilders, what causes it in people who are very fat? LH: We believe that what stresses the glomeruli is the amount of fluid they must filter. Think of it as a question of volume and blood flow. In both increased lean and fatty body mass there’s an increase in blood and plasma volume that needs to be filtered. We use the term glomerular filtration rate, or GFR, to express how much e
