An 11-year study of 24 California cities suggests that more compact and connected street networks with fewer lanes on the major roads are correlated with reduced rates of obesity, diabetes, high blood pressure, and heart disease among residents, although proving causation was not feasible in this study.
Marshall, Wesley E., Daniel P. Piatkowski, and Norman W. Garrick. (2014). Community design, street networks, and public health. Journal of Transport & Health, 1(4), 326-340.