Fat or obese? The labels we use to describe heavy-weight individuals can dramatically influence the judgments we make about people, a new study suggests.

Using the term "obese people" results in more negative judgments than does the term "fat people", even when there is no objective difference between the two groups, research shows.

"The study reinforces earlier findings that, given the choice between fat and obese, the term fat is the lesser of two evils," says University of New South Wales psychologist, Dr Lenny Vartanian.

The research, published in the journal Eating and Weight Disorder adds to a growing body of evidence that labels assigned to social groups can impact people's perceptions of that group.

Dr Vartanian's findings challenge the wisdom of recent calls to adopt a "tough love" approach to the obesity epidemic. In July both the UK health minister and the Victorian president of the Australian Medical Association said calling some obese people fat might be the nudge they needed to start losing weight.

"It is important to understand the impact that different terms have on perceptions of heavy-weight individuals," Dr Vartanian says.

"Research tells us that shaming overweight and obese people into changing their diet and exercise behaviour does not work — it actually backfires, causing them to be less likely to diet and exercise."

Dr Vartanian says one of the reasons the clinical term 'obese' is perceived as more negative and more alien could be because obesity is perceived as a medical problem, while the term fat is something we are more familiar with.

"We are all a little bit fat, we all know someone who is fat — it's a concept we deal with regularly," he says.

The findings suggest that people's perceptions are not based on logic but on emotional responses to words. "Recent evidence also suggests that disgust plays an important role in judgments of obese individuals," Dr Vartanian says.

In the study, a target group of 425 undergraduate students were asked to answer questions about a range of social groups, including heavy-weight individuals. Compared to fat people, obese people were rated as less favourable and more disgusting.

In addition, participants saw themselves as being less similar to obese people, and as less likely to become an obese person than a fat person.

"This is further evidence that how a target individual or group is labelled can impact people's perception of that target," Dr Vartanian says.

"Researchers investigating weight bias should be aware that the specific terms used to refer to overweight people can impact how we perceive the scope of the problem."

Contacts: Dr Lenny Vartanian | 02 9385 8758