The exact amount of weight loss or weight gain to be deemed attractive has been realised. Researchers at the University of Toronto claim that a change of 1.3 kilogrammes per square meter in body mass index (BMI) can make people more attractive.

"Women and men of average height need to gain or lose about 8 and 9 pounds for anyone to see it in their face,” Social Perception and Cognition research at the University of Toronto head, Nicholas Rule, said in a press release. “But they need to lose about twice as much for anyone to find them more attractive."

The team focused on the perception of weight in the face, which is an accurate indicator of a person's BMI. This is calculated as a person's weight in kilogrammes divided by the square of the person's height in metres (kg/m2). A photo collection was created consisting of faces of both men and women between the ages of 20 and 40 years.

The participants had neutral expressions, no facial adornments and neatly tied hair. They altered each photo so every face shows a gradually increasing weight.

The participants were asked to draw out photos they thought looked heavier and attractive. Approximately 1.33 kilogrammes per square metre is required to make a difference noticeable. The team determined that with average height, a weight reduction of 6.3 kilogrammes for women and 8.2 kilogrammes for men are needed to be perceived as attractive.

“The difference between the groups suggests women's facial attractiveness may be more sensitive to changes in weight," Rule said. "This just means women attempting to lose weight need to shed slightly fewer pounds than men for people to find them more attractive."

BMI is a robust indicator of health according to Rule. Increased facial fat tissue is associated with poor cardiovascular health, compromised immune system, frequent respiratory infections and mortality. Even a tiny decrease in BMI can improve anyone’s health.

"When it comes to incentives for weight loss, some people are more motivated to look attractive than to improve their health," said the study’s co-author, Daniel Re. Many people lose weight without the keeping the idea of being healthier in mind. Low body weight is commonly described as more attractive and it attracts potential partners.

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