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Can fitness counter fatness?

Chika Anekwe, M.D., M.P.H., Harvard Health Blog on

Published in Health & Fitness

In a recent study, researchers attempted to answer the very question posed in the title of this post. Before delving into the findings of this study and how it fits with what we already know about this topic, let’s define some key terms.

What do we mean by fitness and fatness?

Fitness, also referred to as cardiovascular fitness or cardiorespiratory fitness (CRF), is a measure of the performance of the heart, lungs and muscles of the body. Muscle performance includes measures of both strength and endurance. Because of the connections between the mind and body, fitness also has an effect on mental alertness and emotional stability. Maximal oxygen consumption (VO2 max), a laboratory measure of the maximum amount of oxygen a person can use during exercise, is the optimal measure of CRF. However, self-reported physical activity is often used as a proxy for VO2 max in research studies because it’s much easier and less expensive to assess.

Fatness, as I discussed in an earlier blog post, can be defined in many different ways. Body mass index (BMI), a calculation of your size that takes into account your height and weight, is used most commonly. However, we know that measures such as body fat percentage, waist circumference, waist-to-hip, ratio and waist-to-height ratio tell us much more than BMI about a person’s health, metabolic risk, and risk of death. Still, due to the ease and relative inexpensiveness of this measurement, BMI is used most commonly in research studies.

What was the goal of the research study?

Going back to the recent study published in the European Journal of Preventive Cardiology, researchers wanted to examine the “fit but fat” paradox. As described by some studies, the fit but fat paradox suggests that individuals with obesity who are also active can experience a reduction in cardiovascular disease risk that supersedes the effect of their increased weight.

 

To address this paradox, our researchers assessed the association between different BMI categories and physical activity levels and the prevalence of three major cardiovascular disease (CVD) risk factors: hypertension (high blood pressure), high cholesterol, and diabetes. This was a large, observational, cross-sectional study that compiled data from 527,662 participants at one specific point in time, without any follow-up period.

They used the standard BMI cutoffs to categorize people as normal weight, overweight, and obese. Physical activity levels were as follows: inactive (performing no moderate nor vigorous physical activity); insufficiently active (less than 150 minutes per week of moderate activity or less than 75 minutes per week of vigorous physical activity); and regularly active (150 minutes or more per week of moderate physical activity or 75 minutes or more per week of vigorous physical activity, or a combination of the two).

What were the results of the research study?

The researchers concluded that being regularly active or insufficiently active was protective against hypertension, high cholesterol, and diabetes, compared to being inactive. The protection was dose-related for hypertension and diabetes, meaning that higher activity levels reduced risk to a greater degree.

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