London (BBC): Researchers say current exercise guidelines are unrealistic and argue that doctors should sometimes advise small increases in activity instead. They warn the 150-minute weekly target is beyond the reach of some people - particularly older individuals. And striving to reach these goals could mean the benefits of lighter exercise are overlooked. But public health officials say current recommendations have proven benefits in lowering the risk of heart disease. There is mounting evidence that inactivity is linked to heart disease, type 2 diabetes and some types of cancer.

UK guidelines for adults recommend at least two-and-a-half hours of moderate activity a week.