Dr. Robert Lufkin is a radiologist who calls himself a “medical school insider.” He’s taught at the David Geffen School of Medicine at UCLA, and the Keck School of Medicine of the University of Southern California.

Lufkin believes in Western medicine, noting it has transformed the world for the better with surgery and medicines that save people's lives. But he’s horrified by the such as obesity, Type 2 diabetes and heart disease. “For most of these diseases, the pills and surgeries don’t address the root cause, and the disease continues to get worse and worse and worse.

They just sort of mask the symptoms," Lufkin, who holds a medical license in California, tells TODAY.com. Lufkin believes lifestyle is key to preventing chronic disease and writes about his advice in the new book, “ ” He doesn’t believe they’re intentional lies since medical knowledge is always evolving and doctors have to constantly re-evaluate things they thought were true.

But he’s critical of what he calls the "currently accepted dogma" in medical school, which is often presented without any alternative theories, he notes. Lufkin says these are three of the “lies” he taught in medical school. TODAY.

com also reached out to medical specialists in each field for their take on what he believes. The interviews were edited and condensed for clarity: The obesity lie is that to lose weight, just exercise more and eat less. This advice doesn’t work.

Exercise has . Unfortunately, because .