We all have that friend who goes hard on the fried food and eats Hot Pockets for dinner but never gains weight. And although they may be thin—and therefore seen as “healthy”—that may not be the case.
If someone has a naturally slender physique but doesn’t eat well-balanced meals or exercise regularly, they fall under the buzzy term, “skinny-fat.” That’s because despite being able to fit into a size 2 jean, they probably have more fat—and less muscle—than is ideal.
When it comes to your health, the key isn’t your weight—it’s your body composition, according to Gabrielle Lyon, D.O., of the Four Moons Spa in San Diego. For example, your BMI might be within the ‘healthy’ range (18.5 to 24.99, according to the World Health Organization), but you can still have a body fat percentage that’s considered overweight (that’s above 20 percent for guys and 30 percent for women, according to Sports Nutrition, Second Edition).
What Skinny-Fat Looks Like
Docs refer to people who are ‘skinny-fat’ as ‘thin on the outside, fat on the inside,’ or ‘TOFI,’ says Dana Simpler, M.D., internal medicine specialist at Mercy Medical Center in Baltimore. There’s no single definition of what a skinny-fat body looks like, but generally someone will have very little muscle tone and probably some flab, especially around their belly and glutes.
They may also notice cellulite on their thighs, arms, and stomach, adds Tom Holland, C.S.C.S., exercise physiologist and author of Beat the Gym. About 90 percent of women and 10 percent of men have some cellulite, but it may be especially noticeable on those with skinny-fat body types, because they don’t have muscle definition, which can actually smooth and lessen its appearance, says Holland.
Related: Is There Anything You Can Really Do To Get Rid Of Cellulite?
Typically, someone who doesn’t overeat, does cardio regularly but doesn’t strength train, or just has a strong metabolism, fits the ‘skinny-fat’ profile, says Simpler. So even though they eat the wrong kinds of foods (think sugar and stuff high in saturated fats, like red meat, cheese, and anything fried), they stay pretty thin, she says.
Why It Can Be An Issue
While being skinny-fat may not sound so bad, the type of diet many skinny-fat people ‘get away with’ can lead to cardiovascular issues, like heart attack or stroke down the road, Simpler says. It can also lead to prediabetes (meaning your blood sugar is higher than it should be but not quite at the level of having diabetes yet), says New York-based nutritionist Jessica Levinson, R.D. “Though type 2 diabetes is generally associated with being overweight, there are people who are at a normal weight who can develop prediabetes after eating too much sugar over time,” she says. So someone who is thin but doesn’t eat well can be a lot less healthy than someone who eats healthy but weighs more.
Related: 8 Foods That Pack A Surprising Amount Of Sugar
Plus, being slender doesn’t mean you’re safe from the risks of having too much fat. Visceral fat—which is stored in your tummy near many of your organs—in particular, can be an indicator of health problems to come, says Levinson. According to Harvard Medical School, it’s linked to higher cholesterol and insulin resistance. And because this particular fat hides deep within the body (it’s not the kind you can grab), skinny-fat people may have more than they realize.
Additionally, skinny-fat people are weaker and have less physical stamina than people who have more muscle, says Lyon. That’s because muscle is full of mitochondria, the engines that power all of your cells—so the less muscle you have, the less strength and energy you’re able to produce. As a result, skinny-fat folks may feel generally sluggish and get winded walking up the stairs. Because women generally have less muscle mass then men—and a harder time building it—they fall into the skinny-fat category more often.
Muscle Up
So what can you do if you think you’re living the skinny-fat life? There are two orders of business: Eat a healthier diet and build muscle.
“Being thin does not guarantee good health if someone is not mindful of what they eat,” says Simpler. “The safest and healthiest diet to prevent or reverse heart disease and diabetes is a whole food, plant-based diet.”
That means cutting back on highly-processed, high-fat foods, and boosting your intake of green and starchy veggies (like kale and sweet potatoes), fruits (like strawberries and blueberries), whole grains (like quinoa and barley), and legumes (like chickpeas and lentils).
To build that muscle, you’ll need to up your protein intake and strength train regularly, says Lyon. (This part is especially important if you’re over 35, when building muscle becomes more difficult.) Try to eat at least 90 grams of protein—which your body breaks down into amino acids to repair muscle tissue—per day, split evenly across breakfast, lunch, and dinner, she says. Look for lean sources like chicken, fish, turkey, beans, and Greek yogurt, suggests Atlanta-based dietitian Kristen Smith, R.D.
Related: Get your daily fill of protein with powder supplements and bars.
In addition, incorporate 20 minutes of strength training into your routine two or three times a week, says Holland. Start with one to three sets of 10 to 15 reps of basic bodyweight moves like squats, pushups, planks, and lunges. As you build strength, increase the number of sets you perform and add some weighted movements—like chest presses and bent-over rows— into the mix. Make sure to use weight that is challenging for the last few reps, but doesn’t throw off your form, Holland says.