By Sarah Jackson, on 18 October 2016
Stigmatisation of obesity remains one of “the last acceptable forms of prejudice”. People with obesity are widely stereotyped as lazy, weak willed and personally to blame for their weight by the media, employers, educators, health care professionals, and even their friends and family.
Facing discrimination can understandably be very stressful in the moment. Small experiments have shown that asking people to watch a video that stigmatises obesity, or telling them that their body size and shape are unsuitable to take part in a group activity, increases levels of the stress hormone cortisol in their saliva.
But what wasn’t known until now was whether discrimination has lasting effects on stress levels. This is important because acute (short-term) stress is a protective, adaptive response whereas chronic stress can have a damaging effect on the body.
In a new study published last week in Obesity we explored the relationship between weight discrimination and chronic stress. The research involved 563 men and women with obesity (body mass index ≥30) aged 50 years and older taking part in the English Longitudinal Study of Ageing (ELSA), a large population-based cohort of middle-aged and older adults living in England.
Rather than measuring levels of cortisol in saliva, which are sensitive to daily fluctuations and short-term factors such as diet, we analysed cortisol levels in hair. Measuring hair cortisol is a new technique that gives an indication of average levels of cortisol in the body over several months. Hair grows at approximately 1 cm per month, so the 1 cm of hair nearest to the scalp represents average exposure to cortisol over the last month.
We found that one in eight people with obesity had experienced discrimination because of their weight, ranging from lack of respect or courtesy to being threatened or harassed. Among people with severe obesity (BMI ≥40), one in three reported discrimination.
Importantly, our findings revealed that average levels of cortisol in hair were 33% higher in individuals who had experienced weight discrimination than those who had not. People who experienced more frequent weight discrimination had higher hair cortisol levels than those who faced less regular discrimination.
The results of this study provide evidence that weight discrimination is associated with the experience of stress at a biological level. Because experiencing high levels of cortisol over a prolonged period can have a substantial impact on health and wellbeing, it is likely that weight discrimination contributes to many of the negative psychological and biological consequences of obesity. In addition, cortisol is known to increase appetite and fat storage, making people who experience weight discrimination more likely to gain weight.
Jackson SE, Kirschbaum C, Steptoe A. Perceived weight discrimination and chronic biochemical stress: A population-based study using cortisol in scalp hair. Obesity. First published ahead of print 14 October 2016. doi:10.1002/oby.21657