I hate to admit it, but Steve was right. Years ago, I directed a hospital-based weight-loss program. In addition to the nutritional advice from the hospital dietitian and the psychology groups and individual counseling sessions I provided, the program included a beginning aerobic class for the participants. Steve, a personal trainer at the hospital-owned gym, was tasked with leading the twice-weekly “aerobics for beginners” class. My group meetings and individual counseling sessions had two parts: changing eating behaviors and overcoming the emotional issues, typically including depression and low self-esteem, that are associated with obesity. I disagreed with Steve when he said that physical activity would lift mood and improve self-esteem. Now, several decades later, research shows that Steve was right. A paper in the British journal, BMJ, reviewed 218 studies that included over 14,000 participants. They found that, compared with control subjects, walking or jogging, yoga, strength training, mixed aerobic activities, and tai chi or qigong were associated with moderate reductions in depression. The reviewers noted that the effects on mood were proportional to the …