The more you weigh, the more likely you are to underestimate your true size, according to new Gravitas research

By Editor

March 9, 2010

The more you weigh, the more likely you are to underestimate your true size, according to new research that reveals fascinating insights into the way severely overweight patients undergoing assessment for weight loss surgery see themselves. 

According to the study, carried out by leading bariatric (weight loss) surgeon David Kerrigan and his team at Gravitas, 50% of patients surveyed had a distorted perception of their body image, making them unable to identify their correct body shape when shown a selection of images ranging from underweight to massively obese. 

Yet while one in three patients with a body mass index (BMI) under 50 in this group overestimated their size, over three quarters of those who had a BMI over 50, ie the super-obese, thought they were actually lighter than they were. 

As Mr Kerrigan points out, the findings may explain why certain patients allow themselves to go on gaining weight when they are already clearly massively obese.

“What is particularly interesting about these findings is that having a BMI of over 50 seems to represent a threshold that once crossed is associated with denial, underestimation of weight gain and thus progression to ever-more severe degrees of obesity,” says Mr Kerrigan, who advised the government on the NICE obesity guidelines used today. 

“It is perhaps not surprising to discover that some lighter patients with a weight problem think they look bigger than they do. This may be because they feel guilty, embarrassed and dogged by low self-esteem and depression, and therefore have a tendency to an exaggerated perception as to how large their body is.

“But there seems to come a point at which patients start to bury their heads in the sand and go into denial about the true extent of their weight problem, which may lead them to abandon on-going attempts at weight control,” adds Mr Kerrigan, who is medical director at Gravitas.

For the study, Gravitas researchers asked 112 patients undergoing assessment for weight loss surgery to identify their correct body shape from a selection of standardised silhouettes ranging from underweight through to massive obesity.

The survey revealed: 

• Half (50%) of all obese patients surveyed could not correctly identify their current body shape
• This distorted self-perception was most marked in the super-obese (BMI >50), over three quarters (77%) of whom were unable to identify their true body shape with any degree of accuracy
• All super obese patients who were unable to identify their body image correctly underestimated their size
• Of the one in three obese patients with a BMI under 50 who incorrectly identified their body shape almost all overestimated their size

Mr Kerrigan added that a reassuring finding from the study was that most patients had realistic expectations of what weight loss surgery can deliver, although a third wanted to end up with a normal body mass, something weight loss surgery rarely delivers. However, a worrying 5% chose a silhouette that was underweight when asked to identify the body shape they felt represented an ideal outcome from surgery.

“This simple screening technique may prove useful in identifying the small number of patients with significant mental health issues manifesting themselves as a desire for extreme degrees of post-operative weight loss, who should be guided towards psychological support rather than surgery in the first instance,” said Mr Kerrigan. 

The findings of the study were presented recently at the inaugural Scientific Meeting of the British Obesity and Metabolic Surgery Society (BOMSS), which awarded Gravitas the BOMSS Council Prize for the best research presentation.

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