Is Being Fat Necessarily Unhealthy? The ‘Obesity Paradox’


Most people associate obesity with poor health. Evidence suggests that perhaps this isn’t always the case. In fact for certain chronic health conditions, it seems that those with a higher BMI can have a better prognosis.


What is body mass index? (BMI)

BMI is calculated by dividing your weight (in kilograms), by your height (in meters) squared. A result of greater than 25 is classified as ‘overweight’, greater than 30 ‘obese’ and greater than 40 ‘severely obese’. It’s a method of classification used by researchers to determine the risk of developing certain diseases at different levels of obesity. One of the advantages of BMI is that it can be easily measured and applied practically. Research indicates there is a strong link that people with high levels of obesity are at greater risk of heart disease due to high cholesterol, blood sugar and blood pressure.


The Problem with BMI

Like any system of classification BMI has some failings. A high BMI usually indicates high levels of obesity, but not always. For example, a 180cm tall body builder weighing 100kg of lean muscle has the same BMI of 30 (ie obese) as a sedentary 180cm tall person with little lean muscle and much body fat. Despite having the same BMI, the sedentary person is in a less healthy position.


While this is an extreme example for illustrative purposes, it does demonstrate that weight and BMI are not the only predicators of health. Visceral fat, (the weight you carry around your abdomen and internal organs) may be one of many better indicators.


What is Metabolically Healthy Obesity (MHO)?*

Metabolically healthy obesity is a term coined due to emerging evidence suggesting that not all overweight or obese people are unhealthy.


It was with much surprise that researchers investigating people with established chronic diseases such as heart and kidney disease found those who were mildly obese, had a better prognosis than lean patients with the same conditions. There are many theories as to why this may be the case but it is believed fitness and muscle mass plays a role.


Furthermore, it has been found being unfit doubles your overall mortality regardless of BMI (ie even if you are ‘thin’). People who are obese but fit have a similar mortality to fit normal-weight individuals. Perhaps most unexpected is that overweight or obese people who are fit have a better long-term prognosis than underweight or lean patients who are unfit.

Cardiologist and researcher Dr Carl Lavie^ estimates one quarter of normal weight individuals are metabolically unhealthy, while half of overweight and one third of obese people are metabolically healthy.

It’s worth commenting the ideal health position is probably to be lean and fit, and being very obese is certainly associated with poor health outcomes but as discussed, the emerging evidence strongly suggests fitness is a much better indicator of long-term prognosis than weight.


If Not Weight and BMI, What Should We Focus On?


Dieting doesn’t work in the long term#. It’s considered to compound ‘obesity’ and plays a significant role in causing eating disorders. Taking the focus away from ‘weight’ and redirecting our efforts towards health and fitness is a more helpful approach.


We all live in different healthy body shapes and sizes, so take a kind and nurturing approach to your body. Don’t feel guilty about food or restrict what you eat, rather enjoy all foods in a mindful way. Check in with yourself to see if you’re hungry before eating or perhaps eating for another reason. Exercise has countless health benefits, the least important of which is ‘weight loss’. Regular movement of any sort is a great start.




* Healthy obese versus unhealthy lean: the obesity paradox, Lavie, C. J. et al. Nat. Rev. Endocrinol. 11, 55–62 (2015); published online 30 September 2014; doi:10.1038/nrendo.2014.165 

# Shaw, K., O’Rourke, P., Del Mar, C., & Kenardy, J. (2005). Psychological interventions for overweight or obesity. The Cochrane Database of Systematic Reviews, (2), CD003818.

^ Podcast – Underground Wellness Radio 21/3/15 #324 “Dr Chip Lavie: The Obesity Paradox”

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