The government’s official definition of a healthy weight should be scrapped because it triggers eating disorders and has become a justification for body shaming, MPs have said.
Body mass index (BMI) forms part of a “dangerous” obesity strategy that is contributing to a rise in body image anxiety, an inquiry concluded.
The women and equalities committee of MPs called for the BMI — an index based on the relationship between a person’s height and weight — to be replaced by a “weight neutral” approach.
Caroline Nokes, Tory chairwoman of the committee, said: “The use of BMI as a measure of healthy weight has become a kind of proxy or justification for weight shaming. This has to stop.”
Clinicians and obesity campaigners last night rejected the calls, with one expert saying that obesity could be an eating disorder too.
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BMI is commonly used by NHS clinicians to assess whether a patient’s health is at risk from being overweight or underweight and to determine whether further intervention is needed.
The MPs are calling for it to be replaced by the US-founded “health at every size” approach, which has been adopted by the controversial fat acceptance movement. It encourages exercise and healthy eating but without the goal of weight loss.
Some 61 per cent of adults and 66 per cent of children feel negative or very negative about their body image most of the time, according to the committee’s report. University College London found that in 1986 only 7 per cent of adolescents said they had exercised to lose weight, while in 2015 the figure was 60 per cent.
“We have been hugely saddened to hear of the number of people who have faced appearance and weight-based discrimination when accessing NHS services,” the report states. “The use of BMI inspires weight stigma, contributes to eating disorders, and disrupts people’s body image and mental health. Public Health England should stop using BMI as a measure of health.”
The government’s obesity strategy is “at best ineffective and at worst perpetuating unhealthy behaviours”, the committee claimed as it called for an independent review of the strategy.
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The strategy includes plans for calorie labels in restaurants and takeaways and for doctors to prescribe a 12-week slimming plan to patients whose BMI and other factors such as waist circumference class them as obese.
An estimated 35 million adults in Britain are overweight or obese with a BMI of 25 or above, roughly 63 per cent of people in those age groups.
Experts welcomed the committee’s call for an increase in funding to gather vital evidence on eating disorders, but the suggestion to scrap the BMI metric caused concern.
Dr Jennifer Logue, clinical reader in metabolic medicine at Lancaster University, said: “Obesity is in many cases an eating disorder and we shouldn’t be pitting the two against each other.”
Professor John Newton, director of health improvement at PHE, said: “BMI is a relatively easy way to assess obesity that requires no specialist equipment.”
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Tam Fry, spokesman for the National Obesity Forum, said: “If the committee wants to scrap the measure it has to suggest a viable and better one.”
Paul Jenkins, associate professor of clinical psychology at the University of Reading, added: “The problem is not BMI but how we use and interpret it.”
BMI is a quick and easy way of working out whether someone is in a healthy range using height and weight (Katie Gibbons writes).
It is fairly accurate and most doctors agree it is the best method available that can be measured simply in a clinic. In the UK a healthy BMI lies between 18.5 and 24.9. Anyone with a BMI of 25-29.9 is overweight; levels of 30 and above are classed as obese.
However, since it was introduced as a simple way of monitoring the weight and health of populations there has been growing criticism that it does not take into account muscle mass, bone density, overall body composition or racial and gender differences, so cannot be an accurate measure of body fat.
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As the calculation does not take into account body composition, some people who are lean and carry a lot of muscle may have a BMI that does not necessarily reflect their health.
However, this is most common in athletes and likely to apply to less than 1 per cent of the population, experts say. Similarly, as people age, they lose muscle and may be classed in the healthy weight range even though they may be carrying excess fat. This is particularly true of smokers or people colloquially termed “skinny fat”.
BMI is also used as an indicator of eating disorders and in some cases sufferers are not considered ill enough for treatment if their measurement fits within the healthy range.
A BMI calculation does not take into account where on the body the fat is stored, which can be a key indicator of risk. Research shows that people who carry a lot of fat around their waist are at higher risk of health problems than those with more fat around their thighs.
Many doctors recommend measuring the waist and height ratio too by dividing the first by the latter. A reading of 0.49 or above in a woman, and 0.53 or above in a man, is regarded as overweight, and over 0.54 and 0.58 respectively as seriously overweight.
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Because of the factors contributing to inconsistencies, there is a growing movement to scrap BMI measurements as an indicator of health.
How to monitor your weight
1. Step on the scales, first thing in the morning and preferably naked.
2. Calculate BMI by dividing your weight in kg by your height in metres. Divide the answer by your height again.
3. Measure your waist, divide figure by your height.
