Choosing active forms of transport, like biking to work, may yield several health benefits, but researchers from New Zealand’s University of Otago say it can come with a surprising downside: a potential rise in greenhouse gas emissions.

In their paper published in Scientific Reports, the team investigated the effects of shifting from passive modes of transport, including driving, to active modes, like walking and cycling. People who select active modes have higher caloric needs, which can lead to an increase in climate-warming emissions related to food production.

The study authors say that, to maximize the climate benefits that are possible from increasing active transport in economically developed countries, we also need to address dietary patterns, including the higher food intake required to fuel the extra exercise. They say emissions associated with active transport will be lower if a walk to the grocery store or a bike ride to the workplace is powered by lower-carbon food choices, namely less meat and fewer resource-heavy processed foods in favor of whole-food options like fruits, vegetables and legumes. In other words, we need to be powering that power walk with an apple instead of a packaged energy bar.

See also: Healthy Food, Healthy Planet