Obese people who participate in a weight loss programme based on exercise and lifestyle changes may have improvements in their mood as a result, according to a new review.
How much weight they lost didn't seem to matter, and it's not even clear that weight loss itself played a role, one expert said.
Previous research has suggested that by losing even a small percentage of their body weight, heavy people can improve their physical and mental health, even if they remain obese. But some weight loss medications have been linked to depression and suicidal behaviour. To complicate things even further, many antidepressants lead to weight gain, not loss.
The new report is not meant "to imply that weight loss is a substitute for treatment of clinically significant depression," said Dr Anthony Fabricatore, whose findings appeared online in the International Journal of Obesity.
Dr Fabricatore now works for the diet and weight loss company Nutrisystem. For the report, when he was at the University of Pennsylvania School of Medicine, he and his colleagues reviewed 31 randomised trials exploring the relationship between weight loss in a structured programme and changes in symptoms of depression.
Overall, almost 8,000 people were part of the studies.
Because most weight loss studies do not include people suffering from clinical depression, Dr Fabricatore and his colleagues focused on symptoms related to depression and mood, rather than tracking who had been diagnosed with clinical depression.
As a whole, people in almost every kind of weight loss programme not based on medication saw improvements in their mood.
Lifestyle modification programs had the most positive effect, and programmes including workouts also relieved symptoms of depression. Treatment with weight loss medication, however, had no impact on mood.
How much weight each person lost - or didn't lose - was not linked with their changes in mood during the weight loss programme.
Dr Fabricatore said that because people in weight loss programmes such as these generally lose about 5% to 10% of their initial body weight, it could be that after a certain point, more weight loss doesn't improve mental health. "There may be a threshold value that once you lose a certain amount of weight, your mood's going to improve and losing more weight isn't necessarily going to make it better," he said.
Shedding pounds might also not be the only explanation for improvements in mood, said Dr Patrick Smith, researcher at Duke University Medical Centre in Durham, North Carolina, whose study was included in the review.
"The other possible explanation is that many of these weight loss programmes are conducted in a group manner, which provides some social support and some validation from other people," which could help improve symptoms of depression, he said. (Reuters Health/ March 2011)