If money were no object, and you had to choose a vehicle that would perform better and last longer, would you pick a powerful Mercedes-Benz G-Class with a 4.0-liter V8 engine or a smaller Honda Civic with a 2.0-liter 4-cylinder engine? Most would go for the Mercedes, not because it’s bigger, but because it has a stronger engine. The same concept applies to the human body fitness matters more than size.
It’s possible to have obesity and still be fit, just as someone at a normal weight can be unfit. In fact, low fitness is a greater health risk than obesity itself. A large-scale study found that low fitness poses a risk of death comparable to or even higher than smoking, diabetes, and heart disease. Yet, conversations about weight loss dominate health discussions, while fitness levels remain in the background.
Understanding Low Fitness
Fitness exists on a spectrum, with frailty at one extreme and peak fitness at the other. Frailty isn’t just a concern for older adults declining physical activity levels mean younger people are becoming pre-frail as well. While fitness is harder to measure than frailty, it’s clear that many adults aren’t meeting physical activity guidelines. Almost half of the population fails to engage in enough aerobic and strength training activities, which impacts cardiorespiratory fitness the best marker of overall fitness.
Fitness isn’t just about endurance or muscle strength; it affects the body on a cellular level. A fit person has a stronger heart, muscles that extract oxygen efficiently, and a greater number of mitochondria, which are the body’s energy powerhouses. On the other hand, someone with low fitness has reduced metabolic reserves, making it harder for the body to fight infections and handle stress. High fitness levels, however, help manage conditions like diabetes, organ transplants, and even cancer.
The Problem With BMI
Despite the clear importance of fitness, medical assessments still focus heavily on body mass index (BMI). This metric doesn’t differentiate between fat and muscle or indicate how well the body functions. A muscular athlete may fall into the “obese” category, while someone with low muscle mass but a normal BMI may still be at high risk for frailty. Rapid weight loss through medication can also reduce muscle mass, making fitness assessment even more crucial.
A better approach to measuring health includes evaluating cardiorespiratory fitness, muscular strength, and body composition. A VO2 max test is the gold standard for measuring cardiovascular fitness, while grip strength is a simple yet effective measure of overall muscle strength. For body composition, waist circumference is a better indicator of health risk than BMI.
How to Improve Fitness
The goal is simple: improve from where you are now. It’s never too late. Studies show that even individuals in their 90s can significantly increase strength and mobility with resistance training in just a few weeks.
While all exercise is beneficial, strength training at least twice a week is particularly important. Resistance training not only builds muscle but also protects against frailty, which cardio alone cannot prevent. Strength training is especially vital for women, who naturally have lower muscle and bone mass. Bodyweight exercises like squats and lunges can be just as effective as weightlifting.
Beyond exercise, overall health depends on good nutrition, sufficient protein intake, quality sleep, and social well-being. The best approach to long-term health is a combination of these factors. Fitness is not about size it’s about function. Just like a strong engine powers a car, a strong body powers a healthy life.
