“Skinny fat” is a non-medical term for a body that looks slim but lacks muscle tone or strength.

If anyone’s ever called you “skinny fat,” you know it’s not exactly a compliment. Describing your body type this way is confusing or even insulting. Yet, despite its not-so-nice ring, there’s an actual physical phenomenon behind this concept.

Here’s what it looks like to be “skinny fat,” plus what it means for your health.

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Skinny fat isn’t a clinical term. Instead, it’s a general description of having a “normal” or even low weight while having metabolic health problems and lower-than-optimal muscle mass.

Researchers have identified this occurrence when studying populations in Asia, where many people have metabolic disorders like type 2 diabetes but low weight. Some researchers use the term “normal weight obesity” to describe this.

To be clear, if you fit into this category, there’s nothing wrong with your body type. It just might mean you’d like to build more muscle or take care to prevent chronic metabolic conditions like type 2 diabetes or heart disease.

There’s no true definition of “skinny fat,” so it can be hard to pinpoint specific signs. That said, you might fall under this umbrella if your BMI is low (below 18.5) or healthy (18.5-24.9), but you have:

  • high blood lipid levels
  • high body fat percentage
  • high amounts of visceral fat
  • poor muscle tone or low muscle mass
  • Genetics: If your parents and grandparents were “skinny fat,” it’s pretty likely you’re predisposed to be so, too.
  • Fitness: Not exercising enough can decrease physical health, even if you have a normal or low BMI.
  • Diet: Studies show that processed foods are associated with increased visceral fat.
  • Age: With age, “skinny fat” is more common due to increased muscle loss.

Even though your body might look relatively healthy on the outside, having a poor muscle-to-fat ratio or a low fitness level can create some risk factors. According to Harvard Health, having high visceral fat has been linked with:

  • increased inflammation
  • elevated blood pressure
  • increased risk of heart disease, dementia, asthma, and some cancers

Being thin may be a common goal for aesthetics, but thinner doesn’t always mean better for your health. If you’re skinny without a foundation of metabolic fitness, you could still have some of the same risk factors as people with obesity. Consider letting your physical fitness and strength, rather than the number on the scale, be a guide toward better health.