People who count housework as exercise could be fooling themselves, research has suggested.
Including gardening, DIY, vacuuming or cleaning in a tally of weekly exercise may give people a false sense of how active they have been.
Until now, studies have suggested housework counts towards a weekly round-up of moderate activity.
This is despite NHS recommendations saying it does not raise the heart rate enough to count towards the goal of 150 minutes of moderate intensity activity every week.
In the new study, experts researching the idea found that those who counted housework were actually heavier than people choosing other forms of exercise.
This may be due to them overestimating how active they are with housework or eating too much to compensate for their levels of activity, the experts said.
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The study, published in the journal BMC Public Health, followed over 4,000 people, of whom 43% said they met or exceeded the NHS guidelines on exercise every week.
Domestic housework in 10 minute bursts or more accounted for 36% of the reported moderate to vigorous physical activity people said they did.
But when weight and height were taken into account, researchers found that those who counted housework as exercise were heavier than people doing other exercise for the same amount of time.
Among women, just a fifth reached the weekly exercise target if housework was discounted.
The team concluded: "Domestic physical activity accounts for a significant proportion of self-reported daily moderate to vigorous physical activity particularly among females and older adults however such activity is negatively associated with leanness suggesting that such activity may not be sufficient to provide all of the benefits normally associated with meeting the physical activity guidelines."
Professor Marie Murphy, from the University of Ulster, who led the study, said: "Housework is physical activity and any physical activity should theoretically increase the amount of calories expended."
"But we found that housework was inversely related to leanness which suggests that either people are overestimating the amount of moderate intensity physical activity they do through housework, or are eating too much to compensate for the amount of activity undertaken."
"When talking to people about the amount of physical activity they need to stay healthy, it needs to be made clear that housework may not be intense enough to contribute to the weekly target and that other more intense activities also need to be included each week."
Chris Allen, senior cardiac nurse at the British Heart Foundation, said: "Your exercise should make you breathe harder, feel warmer, and make your heart beat faster than usual."
"So, unless your household chores tick all these boxes, they won't count."
"If you're daunted by the prospect of a 150 minute target, think of it in 10-minute chunks."
"It doesn't necessarily mean forking out for a gym membership either - try a brisk walk on your lunch break or make a resolution to take the stairs rather than the lift each morning."