I am in my 50s and sleep badly. I don't exercise and am starting to gain weight that I can't shift. I find myself too exhausted to exercise but too fat not to need to. Any ideas?

It's no surprise that how well and how long you sleep affect how you feel. Lack of sleep reduces the amount of human growth hormone responsible for the body's fat-to-muscle ratio. This, along with a decrease in your resting metabolic rate, partly explains your weight gain. In addition, when you haven't slept well, your body craves energy, causing a release of glucose in the bloodstream. This slows your metabolism and can cause weight gain.

The challenge is to get you out of your negative cycle of feeling too tired to exercise, and try to create a positive cycle with the right balance of sleep and exercise. Walking offers a flexible approach, easing you into activity without your being tied into a class or club for a specific length of time - important when you will feel more tired in the early stages.

To begin with, don't worry too much about pace - the important thing is to get you moving on a daily basis. Walk as far and for as long as is comfortable, working up to longer, brisker walks. Alternate these longer walks with shorter walks. The steady introduction of activity gives your body time to get used to it, reducing the chance of sore muscles - a common excuse to give up too quickly. Supplement with a walk either side of dinner - it aids relaxation while burning calories, and there is evidence that it curbs the number of calories consumed at dinner.

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