Fat Mass Index
Fat Mass Index (FMI) is a ratio that looks at a bodies fat mass in relation to height. FMI is one of the most important considerations when it comes to determining health.
Why track my Fat Mass Index?
Are there other ways to track Fat mass index
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DEXA Scan​​​
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High Accuracy, and typically performed in an office setting
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​Bioimpedance scale
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Less precise, however can be performed at home with a personal scale
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BIA machines
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Better than home scales, these can be found in fitness centers or clinics
Fat mass index (FMI) measures how much fat you carry relative to your height. It's calculated by dividing your total fat mass (in kilograms) by your height (in meters squared)—just like BMI, but it focuses only on fat, not your entire body weight.
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Where BMI uses the combined weight of a person's fat, muscle, bone and water weight into a single input, FMI provides a clearer view of just your fat levels.
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This means someone who is muscular may have a high BMI but a health FMI. And someone with a "healthy" BMI could still have excess fat and health risks - a condition known as normal weight obesity.
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Tracking your FMI helps you understand how much of your body weight is actually fat—and how that affects your health.
Elevated FMI is associated with:
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Higher risk of cardiovascular disease
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Insulin resistance and type 2 diabetes
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Hormonal imbalance
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Joint stress and inflammation
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Increased all-cause mortality
FMI can help identify these risks early, even when your weight or BMI doesn't sound the alarm.
When you are on a health journey, tracking Fat mass index can help
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See fat loss even when the scale doesn't move
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Understand your body beyond just "weight loss"
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Set more personalized goals for fitness and longevity
It’s especially useful during strength training or body recomposition—when fat is decreasing, muscle is increasing, and the scale might not tell the full story.