A $1 increase in gasoline prices over a 7-year period would reduce obesity in the U.S. by 10%, according to a study by Charles Courtemanche of the University of North Carolina that found evidence of a negative association between gas prices and body weight. Gas-price increases are associated with additional walking and a reduction in the frequency with which people eat at restaurants.
Courtemanche estimates that 8% of the rise in obesity between 1979 and 2004 can be attributed to a drop in real gas prices at the time.
Source: A Silver Lining? The Connection Between Gasoline Prices