Acetone in breath of 4 Days Marches participants provides information on fat burning

[Northerner]

The concentration of acetone in breath is a suitable marker of fat burning during physical activity, physicists have shown for the first time. Their study, conducted on walkers taking part in the International Four Days Marches in Nijmegen, the Netherlands, shows that there are differences between healthy walkers and those suffering from diabetes.

http://www.sciencedaily.com/releases/2014/07/140709095501.htm