Review Finds Cardio Fitness Improves Heart Health Independent of BMI

WASHINGTON — Weight loss medications have increased in popularity over the past few years. In many cases, losing excess body fat can improve overall health, but exercise also matters. Exercise has benefits beyond weight loss, and a new review highlights the importance of cardio exercise for one’s heart health, independent of body weight.

Let’s take a look at the review, how cardio exercise can boost heart health and give you tips to start increasing your cardio fitness.

Cardiorespiratory Fitness, BMI, and Cardiovascular Disease

Researchers at the University of Virginia sought to compare how cardiorespiratory fitness and body mass index correlate with the risk of cardiovascular disease and all-cause mortality. The British Journal of Sports Medicine published the new systematic review in November 2024.

First, let’s define a few terms. 

Cardiorespiratory fitness refers to the ability of your heart, lungs, and circulatory system to deliver oxygen to your muscles during exercise. Ample research has shown that higher CRF correlates with a lower risk of cardiovascular disease and all-cause mortality. 

In the review, researchers use CRF to describe individuals as fit or unfit using VO2 max — the maximum amount of oxygen your body can use during exercise. 

• Fit: those with the highest VO2 max, in the 20th percentile or higher.
• Unfit: those with the lowest VO2 max, below the 20th percentile.

Body mass index (BMI) refers to one’s total body weight in kilograms divided by height in square meters. BMI has become a controversial metric and does not always indicate health. Since BMI considers one’s total body mass, it does not consider body fat, muscle mass, or bone weight. A tall person with (or without) a lot of muscle mass may fall into the overweight category, for example. 

In the review, researchers classify participants as: 

• Normal weight: under 25 BMI.
• Overweight: 25 to 29.9 BMI.
• Obese: over 30 BMI.

Cardiovascular disease refers to any disease that affects the heart and blood vessels; the most common example is coronary heart disease, which can lead to myocardial infarction (heart attack), heart failure, stroke, arterial disease and atherosclerosis. 

Putting It All Together:

CVD can occur when there is too much chronic stress on your heart, lungs, and arteries. Increasing CRF by doing regular cardio exercise trains your heart and lungs to withstand good stress.

The CDC recommends that adults get 150 minutes of moderate-intensity cardio exercise per week, 75 minutes of high-intensity cardio exercise, or a combination of both to reduce CVD risk. The recommendations also include two days of muscle-strengthening exercise. 

Review: Cardiorespiratory fitness, body mass index and mortality

The American Heart Association states that obesity increases the risk of CVD. This review investigates whether increasing CRF can decrease CVD risk, even in the BMI categories of overweight and obese.

Participants

The review included 20 studies on 398,716 individuals, 33% female. Previous analyses on this topic included fewer women.

Researchers used a reference group and compared it to five others:

• Reference Group: normal weight, fit.
• Normal weight, unfit.
• Overweight, unfit.
• Overweight, fit.
• Obese, unfit.
• Obese, fit.

Results

Here is what they found.

• All fit groups (normal weight, overweight, and obese) had an equal risk of CVD. Higher BMI did not significantly increase CVD or mortality risk for overweight and obese fit groups when compared to the reference group.
• All unfit groups (normal weight, overweight, and obese) had a two to three times higher risk of CVD and mortality than the reference group.

The takeaways? Overweight and obese fit individuals had the same CVD risk as fit individuals of a normal weight. Unfit individuals in all categories had a higher risk. 

The analysis highlights the importance of CRF for people at higher weights and the risk of low CRF even for people at normal weights. 

Potential Mechanisms

Independent of weight loss, the review highlights the following ways that consistent cardio exercise improves heart health:

• Helps balance blood sugar.
• Improves insulin sensitivity.
• Improves cardiovascular function.
• Reduces chronic inflammation.

How to Increase Your Cardio Fitness

Whatever your current weight, the simplest way to improve your cardio fitness is by walking (if you can). To reach the 150 minutes of moderate-intensity cardio exercise guideline, take a 30-minute walk five times weekly. If you’re not taking any walks, start with one per week, then two, then three, until you reach five.

Other options for cardio exercise include cycling, swimming, elliptical machine, rowing and stair climbing. 

Thirty minutes a day can add up to a longer life with a lower risk of preventable CVD, regardless of weight.

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