We all know that having a healthy lifestyle involves eating properly and exercising regularly - but now you might need to start thinking about the air you breathe too.
Researchers are looking into whether air quality can play a role in our risk of being overweight and developing diabetes and heart disease.
According to evidence gathered so far, two people can eat the same foods and do the same exercise, but one might put on more weight simply because of the quality of the air they breathe.
Traffic smog and smoke from cigarettes are the main concerns.
Apparently tiny particles in polluted air can trigger inflammation and disrupt the body's ability to burn energy.
Scientists from all over the world, including the US and Switzerland and are studying these new findings.
They are also looking at the effects on young children as a mother's exposure can affect a baby's metabolism.
The study is ongoing.