Weight loss is considered a major health goal for people who are obese, but the reality is that few reach a normal weight or keep any lost pounds off, a new study shows.
In any given year, obese men had a 1-in-210 chance of dropping to a normal weight, according to the study, which tracked over 176,000 obese British adults.
Women fared a bit better: Their odds were 1 in 124, the study found.
On the brighter side, people were far more likely to shed 5 percent of their body weight -- which is considered enough to bring health benefits like lower blood pressure and blood sugar.
Unfortunately, more than three-quarters gained the weight back within five years, the researchers reported online July 16 in the American Journal of Public Health.
It all paints a bleak picture, the study authors acknowledged.
And the findings underscore the importance of preventing obesity in the first place, said lead researcher Alison Fildes, a research psychologist at University College London.
However, the study does not suggest that weight-loss efforts are futile, stressed Dr. Caroline Apovian, a spokeswoman for the Obesity Society who was not involved in the research.
"We already realize that it's almost impossible for an obese person to attain a normal body weight," said Apovian, who directs the Nutrition and Weight Management Center at Boston Medical Center.
She said the "stark" numbers in this study give a clearer idea of just how difficult it is.
However, she added, the study was based on medical records, and there is no information on how people tried to lose weight. They might have tried a formal weight-loss program, or they might have tried a fad diet.
"So this has no relevance to how effective weight-loss programs are," Apovian said.
Fildes agreed. On the other hand, she said, the results do reflect the real-world experience of obese people who are trying to shed weight.
"What our findings suggest is that current strategies used to tackle obesity are not helping the majority of obese patients to lose weight and maintain that weight loss," Fildes said. "This might be because people are unable to access weight-loss interventions or because the interventions being offered are ineffective -- or both."
For the study, Fildes and her team used electronic medical records to track weight changes among more than 176,000 obese adults between 2004 and 2014. The researchers excluded people who underwent weight-loss surgery, which is an option for severely obese people.
Overall, obese men and women had a low annual probability of achieving a normal weight -- especially if they were severely obese. The odds were as high as 1 in 1,290 for morbidly obese men.
People did stand a much better chance of losing 5 percent of their body weight: The yearly odds were 1 in 12 for men and 1 in 10 for women.
The success, however, was usually short-lived: 78 percent gained that weight back within five years.
Apovian said that because dramatic weight loss is so difficult, obesity specialists do generally advise patients to set a goal of losing 5 percent to 10 percent of their starting weight.
But as the current findings show, even that can be tough to maintain, she added.
Part of the problem, according to Apovian, is that few obese Americans who are eligible for weight-loss medications or surgery actually do get those therapies.
In the United Kingdom, the study authors said, people trying to tackle obesity usually get a referral from their doctor to a weight-management program, which would typically focus on calorie-cutting and exercise.
The new findings suggest that's insufficient, according to Fildes and her team.
For people who are already substantially overweight, Fildes said, staving off further weight gain is vital.
"We would recommend obesity treatment programs prioritize preventing further weight gain and maintaining weight loss when it is achieved," she said.
But given the battle most obese people face, Fildes said, public health efforts to prevent obesity will be even more important.