Kiara Lewis is Head of Division of Health and Wellbeing and her research specialises in children, physical activity and obesity. Here she comments on the Chief Medical Officer’s recent concerns that being overweight is increasingly being seen as the norm.
Is being overweight a health risk?
“There are a number of issues to consider. One is that overweight and obesity are often used interchangeably to mean the same thing. The World Health Organisation, in 1999, categorised body weight according to Body Mass Index (BMI). A BMI of above 25 was categorised as overweight and obesity as a BMI above 30. Whether or not a BMI in the overweight category is detrimental to health is widely contested with little evidence to support that a BMI between 25-30 is associated with adverse outcomes. In addition, a landmark study by Calle et al. in 1999 found that although obesity increased the risk of mortality in white men and women, the association between obesity and mortality was not significant for African-American men and women. This suggests that not everyone is at the same risk from obesity and that being overweight may not be a cause for concern.
Is obesity the right issue to consider?
“The second important issue to consider is fitness. There is now considerable evidence which shows that individuals who are fit and obese are at no greater risk of Cardiovascular Disease (CVD) or all-cause mortality than their fit and ‘normal’ weight counterparts. In addition, ‘fat but fit’ individuals have substantially lower mortality risk than unfit, ‘normal’ weight individuals. The epidemiological studies which show a relationship between BMI and mortality fail to take into account fitness levels. This suggests to me that what we have ‘normalised’ is an inactive lifestyle and efforts should be focussed on improving fitness, rather than reducing fatness.”
