It’s healthy to have some body fat, but all fat is not created equal. Visceral fat is a type of body fat that’s stored within the abdominal cavity. It’s located near several vital organs, including the liver, stomach, and intestines. It can also build up in the arteries. Visceral fat is sometimes referred to as “active fat” because it can actively increase the risk of serious health problems.

If you have some belly fat, that’s not necessarily visceral fat. Belly fat can also be subcutaneous fat, stored just under the skin. Subcutaneous fat, the type of fat also found in the arms and legs, is easier to see. Visceral fat is actually inside the abdominal cavity, and isn’t easily seen.

The only way to definitively diagnose visceral fat is with a CT or MRI scan. However, these are expensive and time-consuming procedures.

Instead, medical providers will typically use general guidelines to evaluate your visceral fat and the health risks it poses to your body. Harvard Health, for example, says that about 10 percent of all body fat is visceral fat. If you calculate your total body fat and then take 10 percent of it, you can estimate your amount of visceral fat.

An easy way to tell if you may be at risk is by measuring your waist size. According to Harvard Women’s Health Watch and the Harvard T.H. Chan School of Public Health, if you are a woman and your waist measures 35 inches or larger, you are at risk for health problems from visceral fat. The same Harvard T.H. Chan School of Public Health article notes that men are at risk for health problems when their waist measures 40 inches or larger.

Visceral fat is often evaluated on a scale of 1 to 59 when diagnosed with body fat analyzers or MRI scans. Healthy levels of visceral fat stay under 13. If your rating is 13–59, immediate lifestyle changes are recommended.

Visceral fat can start causing health problems immediately. It can increase insulin resistance, even if you’ve never had diabetes or prediabetes. Research has found that this may be because a retinol-binding protein that increases insulin resistance is secreted by this type of fat. Visceral fat can also raise blood pressure quickly.

Most importantly, carrying excess visceral fat increases your risk for developing several serious long-term, life-threatening medical conditions. These include:

Fortunately, visceral fat is extremely receptive to exercise, diet, and lifestyle changes. With each pound you lose, you lose some visceral fat.

When possible, you should exercise for at least 30 minutes every day. Make sure to include plenty of both cardio exercises and strength training. Cardio includes aerobic exercise, like circuit training, biking, or running, and will burn fat faster. Strength training will slowly burn more calories over time as your muscles get stronger and consume more energy. Ideally, you’ll do 30 minutes of cardio 5 days a week and strength training at least 3 times per week.

The stress hormone cortisol can actually increase how much visceral fat your body stores, so reducing the stress in your life will make it easier to lose it. Practice meditation, deep breathing, and stress management tactics.

It’s also essential to follow a healthy, well-balanced diet. Eliminate processed, high-sugar, high-fat foods from your diet, and include more lean proteins, vegetables, and complex carbs like sweet potatoes, beans, and lentils.

Use low-fat cooking methods, such as broiling, boiling, or baking, instead of frying. When you do use oils, go for healthier ones like olive oil instead of butter or peanut oil.

If you are a man and your waist is more than 40 inches, or if you’re a woman and your waist is more than 35 inches, you should make an appointment to see your doctor and discuss health risks and lifestyle changes.

Your doctor can check for health risks associated with high incidence of visceral fat with tests like blood work or ECG scans, and they may refer you to a nutritionist.

Visceral fat isn’t visible, so we don’t always know it’s there, making it that much more dangerous. Fortunately, it’s usually preventable. Maintaining a healthy, active, low-stress lifestyle can prevent visceral fat from building up in excess in the abdominal cavity.