I'm 49, very unfit, juggling a job, an impending empty house and an expanding waistline. I'm desperate to reclaim my fitness and my figure, which I know I have let slip. I live in London and used to love cycling. Is there hope?

Yes! Since you love cycling, I have developed a four-week plan focusing on two themes: cycling for active travel and cycling for pleasure. The former can be incorporated into your normal day, saving you time and money; the latter can be enjoyed with friends. Each week builds up gradually to be achievable while boosting your fitness.

Week 1: cycle to work one morning, leave the bike there and cycle back the following day. On three of your five working days, replace a daily task for which you normally take the car, and instead go on foot or by bicycle. For pleasure, complete one 30-minute and one 45- to 60-minute cycle exploration trip.

Week 2: cycle to work twice and home twice - ideally, break them up, so you don't do too much in one day. For pleasure, cycle to a pub along the Thames towpath.

Week 3: cycle to work on two days and back from work on two days; and on one day cycle both to and from work. For pleasure, take a route from a bicycle touring book.

Week 4: cycle to and from work on at least two days. Finally, for pleasure, dependent on weather, either do two shorter, faster rides of 45 minutes or one longer one of 90 minutes to build up stamina. This longer ride can be broken down into a there-and-back route, but do cycle with a purpose. Good luck.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to Weekend, 119 Farringdon Road, London EC1R 3ER. Email weekend@theguardian.com