Obesity increases the risk of morbidity and mortality and reduces quality of life independent of age, sex or ethnicity. Leading health authorities recommend weight loss as a primary treatment strategy for obesity reduction--weight loss goals range from 5% to 10% of initial body weight. Intentional weight loss in most adults is associated with a reduction in many of the health complications of obesity. Nonetheless, emerging evidence supports the notion that a lifestyle-modification program characterized by an increase in physical activity and a balanced diet can reduce obesity and the risk of obesity-related comorbid conditions despite minimal or no weight loss. The benefits of such an approach include appreciable reductions in abdominal obesity, visceral fat and cardiometabolic risk factors, and increases in both skeletal muscle mass and cardiorespiratory fitness. Individuals with obesity face a serious challenge if they are to attain even modest weight loss in today's obesogenic environment. Clinicians could encourage positive lifestyle changes in their patients by counseling them that obesity and its associated health risks can be reduced in response to an increase in physical activity with or without weight loss.