When people are feeling down, obese people can gain almost a pound, while lean people stay the same size.
Researchers monitored the emotions of more than 2,000 people in Great Britain for nine months.
Each month, people were asked about depressive symptoms, such as not enjoying daily activities or feeling bad about themselves.
More than 90 percent of people in the study did not have clinical depression.
But if overweight or obese people felt more depressed overall, they gained weight a month later.
Initially there was no difference for people with a healthy weight.
It’s known that comfort eating can kick things into high gear during periods of depression, but researchers have now proven that weight gain is likely during episodes of low mood… but only for some
Researchers suspect that overweight and obese people are more prone to eating high-calorie, fatty and sugary foods when they are struggling emotionally.
The study authors gave people a score of 24 for depressive symptoms, based on their answers to the monthly questions.
A score just five points higher than their ‘usual’ average level of depressive thoughts, for obese people, was linked to an average weight gain of 0.8 pounds.
For overweight people, the same increase in negative feelings was linked to a 0.6 pound weight gain.
This kind of weight gain can accumulate over months or years, the researchers warn.
They suggest that diet classes and weight loss apps want to record how people feel as much as their food intake and exercise levels.
Unless you’re overweight or obese, comfort eating during episodes of depression is unlikely to have a major effect on your weight, the study found.
Then people who are struggling can get tips that can help improve their mood, such as online cognitive therapy, mindfulness, listening to music or gardening, before they reach a point where they start eating unhealthy and gaining weight.
Dr. Julia Mueller, who led the research at the University of Cambridge, said: ‘These findings suggest that people who are overweight or obese are more vulnerable to weight gain in response to feeling more depressed.
‘We know from previous evidence that people who feel depressed may overeat, or eat high-calorie foods with more fat or sugar, or be less likely to walk or exercise.
‘Weight gain may only be seen in people with a higher BMI, because these are people with a genetic predisposition to comfort eating or who learned to use food as comfort as a child.
‘Or it could be that they gain weight more easily than people with a lower BMI.
‘We need more research to confirm these results, which could be used to pay more attention to depressive symptoms in people trying to lose weight so that they don’t end up gaining it.’
The study, published in the journal PLOS One, found that depressive symptoms were associated with self-reported weight gain a month later, but that weight gain a month later was not associated with depressive symptoms.
This rules out an alternative explanation that weight gain leads to negative feelings, rather than the other way around.
The people the researchers looked at, aged between 44 and 70 and recruited from doctors’ surgeries in Cambridgeshire for a recent health survey, also answered questions about anxiety and stress.
But these were not linked to weight gain, with researchers speculating that stress and anxiety may cause more intense emotions than depression, such as anxiety and tension, causing people to lose their appetite rather than overeat.