Living on your own could be the key to avoiding obesity

An American study found that women living in households with four or more people were significantly more likely to be obese than those who lived by themselves.

Married women were also more likely to be obese than those who remained single, according to research published in BMC Family Practice.

Cheaper food, lack of exercise and the increasing "couch potato" culture in the UK have been blamed for a rising number of people becoming overweight or obese.

The latest research, conducted by researchers from Texas Tech University Health Sciences Centre, questioned almost 300 women who attended family planning clinics.

Almost half of the women (47.8 per cent) were classified as being obese - defined as having a body mass index (BMI) of over 30. But family circumstances appeared to play a role in determining whether women were obese or not.

While only 32.5 per cent of those who lived alone were obese, this rose to 64.8 per cent of women who lived in households of four or more people. They also found that 44.7 per cent of people who lived with one or two other people were obese.

Married respondents were also more likely to be obese than unmarried people - 58 per cent compared to 42.5 per cent.

Over 60 per cent of women who did not have a high school education were obese, compared to only 40 per cent of those who went on to study further than high school.

The researchers, led by Professor James Rohrer, also found that women who received no support from their parents were more likely to be obese than those who received a lot or some parental support - 52.8 per cent compared to 42.7 per cent.

"The reasons why large families increase the risk of obesity are not entirely clear," Prof Rohrer said. "One obvious mechanism is that larger households are more likely to have greater volumes of food available."

Rates of obesity among adults have almost quadrupled in the last 25 years in the UK, with 22 per cent of Britons now obese. The number of obese children has tripled in 20 years.

Figures estimate that around 10 per cent of six-year-olds are obese, rising to 17 per cent of 15-year-olds.

In the US, rates of obesity are even higher, but experts believe it will not be long before Britons catch up.

The US researchers said the results of their study should be considered suggestive rather than definitive.

"Nevertheless, they have significance for public health practice related to weight control," they said.