John M Westfall, Doug H Fernald

Obesity is an epidemic in the United States. Two-thirds of the population is overweight and does not get enough exercise. Eastern cities are full of escalators that transport obese Americans to and from the subway. Walking stairs is a moderate activity requiring 3-6 metabolic equivalent tasks (METS) and burning 3.5-7 kcal/min. We determined the caloric expenditure and potential weight change of the population of one eastern city if all the subway riders walked the stairs rather than ride the escalators. There are 5,000,000 daily journeys made on the New York City Subway. Subway entrances include a stairway or escalator of approximately 25 steps. Each step up requires 0.11-0.15 kcals; each step down requires 0.05 kcals. To lose one pound requires burning 3500 kcals. We assumed each rider made a round trip so about 2.5 million individual people ride the subway each day. By walking stairs rather than riding escalators, the riders of the New York Subway would lose more than 2.6 million pounds per year. The average subway rider would lose about one pound per year. While this may sound insignificant, in one decade the average subway rider would lose 10 pounds, effectively reversing the trend in the United States of gaining 10 pounds per decade. This conservative estimate of the number of stairs ascended daily means that subway riders might lose even more weight. We believe that this novel approach might lead to other public and private efforts to increase physical activity such as elevators that only stop on even numbered floors, making stairwells more attractive and well lit, and stopping moving sidewalks. The built environment may support small, incremental changes in usual daily physical activity that can have significant impact on populations and individuals.