Enjoying a brisk walk can be better than the gym for keeping weight down, new research has found.
A study from the London School of Economics and Political Science found that people may benefit more from "high impact" walking than other activities, such as going to the gym. The effects were particularly strong for women, and both men and women over the age of 50.
Dr Grace Lordan, who led the research, examined data on how much people exercise from the annual Health Survey for England (HSE) from 1999 to 2012.
She particularly looked for evidence of exercise of moderate intensity - which pumps up the heart rate and causes sweating.
This includes brisk walking, swimming, cycling, working out at a gym, dancing, running, jogging, football, rugby and squash.
Data on body mass index (BMI) and waist circumferences was also checked.
Overall, the study found that brisk walking had the strongest link with good weight control, followed by sports and other forms of exercise.
"We show that individuals who walk at a brisk or fast pace are more likely to have a lower weight when compared to individuals doing other activities," Dr Lordan said.
Men and women who regularly walked briskly for more than 30 minutes had lower BMIs overall and smaller waists.
Due to the fact that walking does not cost anything, the exercise was also good for people on lower incomes.
Dr Lordan, writing in the journal Risk Analysis, said: "Given the obesity epidemic and the fact that a large proportion of people in the UK are inactive, recommending that people walk briskly more often is a cheap and easy policy option.
"Additionally, there is no monetary cost to walking so it is very likely that the benefits will outweigh the costs."
Walking has also been linked to better physical and mental health.
Dr Lordan said: "So, a simple policy that 'every step counts' may be a step towards curbing the upward trend in obesity rates and beneficial for other health conditions."
She said her findings provide an argument for a national campaign to promote walking.
She added that it is estimated almost 80% of the UK population is not meeting the Government's target of doing 150 minutes of moderate intensity activity every week.
This costs the NHS almost £1 billion a year, mainly due to obesity.