The chance of an obese person attaining normal body weight is 1 in 210 for men and 1 in 124 for women, increasing to 1 in 1,290 for men and 1 in 677 for women with severe obesity, according to a study of UK health records led by King's College London. The findings, published in the American Journal of Public Health, suggest that current weight management programmes focused on dieting and exercise are not effective in tackling obesity at population level.

The research, funded by the National Institute for Health Research (NIHR), tracked the weight of 278,982 participants (129,194 men and 149,788) women using electronic health records from 2004 to 2014. The study looked at the probability of obese patients attaining normal weight or a 5% reduction in body weight; patients who received bariatric surgery were excluded from the study. A minimum of three body mass index (BMI) records per patient was used to estimate weight changes.

The annual chance of obese patients achieving five per cent weight loss was 1 in 12 for men and 1 in 10 for women. For those people who achieved five per cent weight loss, 53 per cent regained this weight within two years and 78 percent had regained the weight within five years.

Overall, only 1,283 men and 2,245 women with a BMI of 30-35 reached their normal body weight, equivalent to an annual probability of 1 in 210 for men and 1 in 124 for women; for those with a BMI above 40, the odds increased to 1 in 1,290 for men and 1 in 677 for women with severe obesity.

Weight cycling, with both increases and decreases in body weight, was also observed in more than a third of patients. The study concludes that current obesity treatments are failing to achieve sustained weight loss for the majority of obese patients.

Dr Alison Fildes, first author from the Division of Health and Social Care Research at King's College London (and now based at UCL), said: 'Losing 5 to 10 per cent of your body weight has been shown to have meaningful health benefits and is often recommended as a weight loss target. These findings highlight how difficult it is for people with obesity to achieve and maintain even small amounts of weight loss.'

'The main treatment options offered to obese patients in the UK are weight management programmes accessed via their GP. This evidence suggests the current system is not working for the vast majority of obese patients.'

'Once an adult becomes obese, it is very unlikely that they will return to a healthy body weight. New approaches are urgently needed to deal with this issue. Obesity treatments should focus on preventing overweight and obese patients gaining further weight, while also helping those that do lose weight to keep it off. More importantly, priority needs to be placed on preventing weight gain in the first place.'

Professor Martin Gulliford, senior author from the Division of Health and Social Care Research at King's College London, said: 'Current strategies to tackle obesity, which mainly focus on cutting calories and boosting physical activity, are failing to help the majority of obese patients to shed weight and maintain that weight loss. The greatest opportunity for stemming the current obesity epidemic is in wider-reaching public health policies to prevent obesity in the population.'