Much of the media has reported that discriminatory "fat shaming" makes people who are overweight eat more, rather than less.
The Daily Mail describes how, "telling someone they are piling on the pounds just makes them delve further into the biscuit tin". While this image may seem like a commonsense "comfort eating" reaction, the headlines are not borne out by the science.
In fact, the news relates to findings for just 150 people who perceived any kind of weight discrimination, including threats and harassment, and poorer service in shops - not just friendly advice about weight.
The research in question looked at body mass index (BMI) and waist size for almost 3,000 people aged over 50 and how it changed over a three- to five-year period. The researchers analysed the results alongside the people's reports of perceived discrimination. But because of the way the study was conducted, we can't be sure whether the weight gain resulted from discrimination or the other way around (or whether other unmeasured factors had an influence).
On average, the researchers found that the 150 people who reported weight discrimination had a small gain in BMI and waist circumference over the course of the study, while those who didn't had a small loss.
Further larger-scale research into the types of discrimination that people perceived may bring more answers on the best way to help people maintain a healthy weight.
Where did the story come from?
The study was carried out by researchers from University College London, and was funded by the National Institute on Aging and Office for National Statistics. Individual authors received support from ELSA funding and Cancer Research UK. The study was published in the peer-reviewed Obesity Journal.
The media in general have perhaps overinterpreted the meaning from this study, given its limitations. The Daily Telegraph's headline says, "fat shaming makes people eat more", but the study hasn't examined people's dietary patterns, and can't prove whether the weight gain or discrimination came first.
What kind of research was this?
This was an analysis of data collected as part of the prospective cohort study, the English Longitudinal Study of Ageing (ELSA). This analysis looked at the associations between perceived weight discrimination and changes in weight, waist circumference and weight status.
The researchers say that negative attitudes towards people who are obese have been described as "one of the last socially acceptable forms of prejudice". The researchers cite common perceptions that discrimination against overweight and obesity may encourage people to lose weight, but that it may have a detrimental effect.
A cohort study is a good way of examining how a particular exposure is associated with a particular later outcome. However, in the current study the way in which the data was collected meant that it was not possible to clearly determine whether the discrimination or the weight gain came first.
As with all studies of this kind, finding that one factor has a relationship with another does not prove cause and effect. There may be many other confounding factors involved, making it difficult to say how and whether perceived weight discrimination is directly related to the person's weight. The researchers did make adjustments for some of these factors in analyses, to try and remove their effect.
What did the research involve?
The English Longitudinal Study of Ageing is a long-term study started in 2001/02. It recruited adults aged 50 and over and has followed them every two years. Weight, height and waist circumference have been objectively measured by a nurse every four years.
Questions on perceptions of discrimination were asked only once, in 2010/11, and were completed by 8,107 people in the cohort (93%). No body measures were taken at this time, but they were taken one to two years before (2008/09) and after (2012/13) this. Complete data on body measurements and perceptions of discrimination were available for 2,944 people.
The questions on perceived discrimination were based on those previously established in other studies and asked how often in your day-to-day life:
- you are treated with less respect or courtesy
- you receive poorer service than other people in restaurants and stores
- people act as if they think you are not clever
- you are threatened or harassed
- you receive poorer service or treatment than other people from doctors or hospitals
The responders could choose one of a range of answers for each - from "never" to "almost every day". The researchers report that because few people reported any discrimination, they grouped responses to indicate any perceived discrimination versus no perceived discrimination. People who reported discrimination in any situation were asked to indicate what they attributed this experience to, from a list of options including weight, age, gender and race.
The researchers then looked at the relationship between change in BMI and waist circumference between the 2008/09 and 2012/13 assessments. They then looked at how this was related to perceived weight discrimination at the midpoint. Normal weight was classed as a BMI less than 25, overweight between 25 and 30, "obese class I" between 30 and 35, "obese class II" 35 to 40, and "obese class III" was a BMI above 40.
In their analyses the researchers took into account age, sex and household (non-pension) income, as an indicator of socioeconomic status.
What were the basic results?
Of the 2,944 people for whom complete data was available, 150 (5.1%) reported any perceived weight discrimination, ranging from 0.7% of normal-weight individuals, to 35.9% of people in obesity class III. There were various differences between the 150 people who perceived discrimination and those who didn't. People who perceived discrimination were significantly younger (62 years versus 66 years), of higher BMI (BMI 35 versus 27), waist circumference (112cm versus 94cm) and less wealthy.
On average, people who perceived discrimination gained 0.95kg in weight between the 2008/09 and 2012/13, while people who didn't perceive discrimination lost 0.71kg (average difference between the groups 1.66kg).
There were significant changes in the overweight group (gain 2.22kg among those perceiving any discrimination versus loss of 0.39kg in the no discrimination group), and the obese group overall (loss of 0.26kg in the discrimination versus a loss of 2.07kg in the no discrimination group). There were no significant differences in any of the obesity subclasses.
People who perceived weight discrimination also gained an average 0.72cm in waist circumference, while those who didn't lost an average of 0.40cm (an average difference of 1.12cm). However, there were no other significant differences by group.
Among people who were obese at the first assessment, perceptions of discrimination had no effect on their risk of remaining obese (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.46 to 2.59), with most obese people staying obese at follow-up (85.6% at follow-up versus 85.0% before). However, among people who were not obese at baseline, perceived weight discrimination was associated with higher odds of becoming obese (OR 6.67, 95% CI 1.85 to 24.04).
How did the researchers interpret the results?
The researchers conclude that their results, "indicate that rather than encouraging people to lose weight, weight discrimination promotes weight gain and the onset of obesity. Implementing effective interventions to combat weight stigma and discrimination at the population level could reduce the burden of obesity".
This analysis of data collected as part of the large English Longitudinal Study of Ageing finds that people who reported experiencing discrimination as a result of their weight had a small gain in BMI and waist circumference over the study years, while those who didn't had a small loss.
There are a few important limitations to bear in mind. Most importantly, this study could not determine whether the weight changes or the discrimination came first. And, finding an association between two factors does not prove that one has directly caused the other. The relationship between the two may be influenced by various confounding factors. The authors tried to take into account some of these, but there are still others that could be influencing the relationship (such as the person's own psychological health and wellbeing).
As relatively few people reported weight discrimination, results were not reported or analysed separately by the type or source of the discrimination. Therefore, it is not possible to say what form the discrimination took or whether it came from health professionals or the wider population.
People's perception of discrimination and the reasons for it may be influenced by their own feelings about their weight and body image. These feelings themselves could also be having a detrimental effect against them being able to lose weight. This does not mean that discrimination does not exist, or that it should not be addressed. Instead, both factors may need to be considered in developing successful approaches to reducing weight gain and obesity.
Another important limitation of this study is that despite the large initial sample size of this cohort, only 150 people (5.1%) perceived weight discrimination. When further subdividing this small number of people by their BMI class, this makes the numbers smaller still. Analyses based on small numbers may not be precise. For example, the very wide confidence interval around this odds ratio for becoming obese highlights the uncertainty of this estimate.
Also, the findings may not apply to younger people, as all participants were over the age of 50.
Discrimination based on weight or other characteristics is never acceptable and is likely to have a negative effect. The National Institute for Health and Care Excellence has already issued guidance to health professionals, noting the importance of non-discriminatory care of overweight and obese people.
Much of the media has reported that discriminatory "fat shaming" makes people who are overweight eat more, rather than less. The Daily Mail describes how...
Links to Headlines
Fat shaming 'makes people eat more rather than less'. The Daily Telegraph, September 11 2014
'Fat shaming' makes people put on more weight, study claims. Metro. September 10 2014
Links to Science
Jackson SE, Beeken RJ, Wardle, J. Perceived weight discrimination and changes in weight, waist circumference, and weight status. September 11 2014