"When we feel bad about our bodies, we often turn to loved ones - families, friends and romantic partners - for support and advice. How they respond can have a bigger effect than we might think," said Professor Christine Logel from Renison University College at the University of Waterloo in Canada who led the study.
The study found that women who received a higher number of what the researchers called acceptance messages about their weight saw better weight maintenance and even weight loss than their counterparts who did not receive this positive messaging from their loved ones.
The team of social psychologists asked the women their height and weight, and how they felt about what they see on the scale.
About five months later, they asked them if they had talked to their loved ones about their concerns, and if so, how they had responded.
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About three months after that, they tracked whether their weight and their concerns about it changed in that time.
"On average, the women in the study were at the high end of Health Canada's BMI recommendations, so the healthiest thing is for them to maintain the weight they have and not be so hard on themselves," said Logel.
Overall, the women in the sample gained some weight over time, which is not uncommon for young adults. But if the women got the message from their loved ones that they look fine, then they maintained or even lost a bit of weight.
Women who received comparatively few weight acceptance messages from their loved ones gained almost 4.5 pounds on average, whereas women who received comparatively more weight acceptance messages lost a pound.
The results showed that when women concerned about their weight heard that their loved ones accepted them as they are, they felt better about their bodies, and subsequently they did not gain like other women did.
The research suggests that feeling better about themselves caused the women to be more active or eat more sensibly.
Receiving unconditional acceptance might have lowered their stress, a known cause of weight gain, researchers said.
The study appears in the journal Personal Relationships.