Chris Crowley is his 80-year-old patient--the relentless drum-beater for YOUNGER NEXT YEAR and the living proof that Harry's Rules work: It is possible to turn back the biological clock.
Jen Sacheck, Ph.D., is a nutritionist and exercise physiologist at the Friedman School of Nutrition Science and Policy at Tufts University. Dr. Sacheck lives in Concord, Massachusetts.