My husband was recently diagnosed with type-2 diabetes. His GP advised him to exercise, but when we asked why, and what exercise, he was vague. Can you provide guidance?

Exercise may help in three ways. It promotes long-term weight loss - consistent exercise is more important than what you put in your mouth; it encourages muscles to increase glucose uptake from the blood, and so decreases the need to produce excess insulin; and it increases fat oxidation. All improve insulin sensitivity and reduce the risk of cardiovascular disease.

For people with type-2 diabetes, the American College of Sports Medicine recommends at least 30 minutes of low- to moderate-intensity activity on three to five days a week, on non-consecutive days - that's roughly equivalent to expending 150-200 calories a day or 1,000 a week. That may sound alarming, but this can be achieved through lifestyle exercise - a brisk, mile-long walk, say, burns on average 100 calories; on short trips, walk or cycle instead of driving. Resistance exercise on two days a week is also recommended.

Your husband's insulin resistance and impaired glucose tolerance may mean low initial fitness levels, so encourage him to progress gradually. What's more, your attitude may affect his success: studies show that men have a 40% adherence rate when their spouses have a neutral attitude to their exercise, while it's 80% for those whose spouses are positive. Explore physical activities you can enjoy together now, as well as in the colder months, when motivation tends to wane.

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