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Fit-Fat Paradox Holds For People With Severe Obesity

Regular readers will be quite familiar with the findings that cardiometabolic health appears to be far more related to “fitness” than to “fatness” – in other words, it is quite possible to mitigate the metabolic risks commonly associated with excess body fat by improving cardiorespiratory fitness.

Now, a study by Kathy Do and colleagues from York University, Toronto, published in BMC Obesity, shows that this relationship also holds for people with quite severe obesity.

The researcher studied 853 patients from the Wharton Medical Clinics in the Greater Toronto Area, who  completed a clinical examination and maximal treadmill test. Patients were then categorized into fit and unfit based on age- and sex-categories and in terms of fatness based on BMI class.

Within the sample, 41% of participants with mild obesity (BMI<35) had high fitness whereas only 25% and 11% of the participants with moderate (BMI 35-40) and severe obesity (BMI>40), respectively, had high fitness.

Individuals with higher fitness tended to be younger and more likely to be female.

While overall fitness did not appear to be independently associated with most of the metabolic risk factors (except systolic blood pressure and triglycerides), the effect of fitness in patients with severe obesity was more pronounced. Thus, the prevalent relative risk for pre-clinical hypertension, hypertriglyceridemia and hypoalphalipoproteinemia and pre-diabetes was only elevated in the unfit moderate and severe obesity groups, and fitness groups were only significantly different in their relative risk for prevalent pre-clinical hypertension within the severe obesity group.

Similarly, high fitness was associated with smaller waist circumferences, with differences between high and low fitness being larger in those with severe obesity than with mild obesity.

Based on these findings, the researchers conclude that the favourable associations of having high fitness on health may be similar if not augmented in individuals with severe compared to mild obesity.

However, it is also apparent based on the rather low number of “fit” individuals in the severe obesity category (only about 1 in 10), that maintaining a high level of fitness proves to be more challenging the higher the BMI.

Edmonton, AB


  1. This is one of the excellent readings I had recently about obesity. The factors for obesity are complex & and multiple. Despite typical wisdom, it is not merely an outcome of overeating. Research has proved that in many cases a powerful, hidden reason of morbid obesity is genetic. The hidden reasons of severe obesity are yet to known. Any how loved the article and will be watching for more readings like this.
    Thank you

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