Why Your Strength Says More About Health Than Your Size
For decades, we’ve been told that thinner is healthier and that carrying extra pounds automatically raises your risk for disease and early death. But new research challenges that assumption in a big way.
This study adds to a growing body of evidence showing that health isn’t defined by size alone—and that strength, metabolic fitness, and resilience matter far more than hitting a particular number on the scale.
A look into the research
Researchers followed over 85,000 adults for five years to see how body weight relates to the risk of death. The participants were grouped by BMI:
- Underweight: BMI <18.5
- Normal weight: 18.5–<25
- Overweight: 25–<30
- Obesity: ≥30
Here’s what they found:
- People who were underweight had the highest risk of early death—2.7 times more likely to die during the study period compared to those at the upper end of the “normal” range.
- Even those who fell within the lower end of a “healthy” BMI (around 20 to 22.5) still had a 27% higher risk of dying early than those closer to a BMI of 24.
- On the other hand, people in the overweight range (BMI 25–29.9) had no increased risk of early death compared to the “normal” group.
- Even those classified as moderately obese (BMI 30–35) didn’t show a higher risk of early death. It wasn’t until severe obesity (BMI 40 and above) that mortality risk more than doubled.
In other words, a little extra weight did not shorten life expectancy, but being too thin was tied to significantly worse outcomes.
Why BMI isn’t the best measure of health
While BMI is widely used, it’s a blunt tool. It only looks at height and weight—it doesn’t distinguish between fat and muscle, or where fat is distributed in the body. That’s a major limitation, because metabolic health (things like blood pressure, insulin sensitivity, and cholesterol levels) plays a much bigger role in long-term outcomes than size alone.
A lean person with little muscle mass may technically fall into the “healthy” BMI category, but could be dealing with malnutrition, low bone density, or frailty that increases health risks.
Meanwhile, someone in the “overweight” category who strength trains, eats nutrient-dense foods, and maintains good cardiovascular health may be far better protected against chronic disease.
Ultimately, BMI can give a rough snapshot, but it can’t replace a focus on strength, nutrition, and overall metabolic fitness as true markers of health.
What this means for your health goals
Instead of chasing thinness, the real goal should be strength and resilience—both physically and metabolically. Here’s how to reframe the way you think about weight and health:
- Focus on strength training: Building muscle improves insulin sensitivity, supports bone health, and helps protect against age-related frailty. Muscle is far more protective than being “thin.”
- Prioritize nutrient density: Aiming for a diet rich in protein, fiber, healthy fats, and colorful plants provides the building blocks your body needs for repair, energy, and longevity.
- Track more than weight: Blood pressure, fasting glucose, VO2 max, and strength metrics tell you far more about your health than BMI ever could.
- Rethink your definition of “healthy”: Shift your focus from the number on the scale to how you feel, move, and nourish your body. Prioritize building strength, maintaining energy, and supporting overall health instead of chasing a specific weight.
The takeaway
This research doesn’t mean that excess weight carries no risks—severe obesity still shortened lifespan in the study. But it does underscore something many health experts have been saying for years: the healthiest body isn’t necessarily the smallest one.
At mindbodygreen, we believe being “fit” isn’t about shrinking yourself; it’s about creating a body that’s capable, resilient, and metabolically healthy. This study backs that up, showing that longevity isn’t about being as thin as possible, but about building strength, fueling well, and supporting your body with habits that keep it thriving for decades to come.
