In the guide, each week has a theme, and there are actions around that theme. It's not a traditional fast (ie. total avoidance for 40 days, then back to old habits). It's more about trying out some ways in which we can live a more planet-friendly, and people-friendly lifestyle.
For those of a christian orientation, there is a bible study to match each theme.
ps. Lent this year is Feb 22 - Apr 7. And for those in the UK, there is a similar (but more British) version run by tearfund.