Understanding BMI and Its Role in NASH Diagnosis

BMI stands for body mass index. BMI is a simple formula that uses your height and weight to determine your weight category. It can show whether you are underweight, of normal weight, or overweight. It also indicates whether you may have obesity.¹

BMI is an easy-to-use tool. It can help signal weight-related conditions, such as type 2 diabetes, metabolic syndrome, and obesity. You can also use BMI to assess your risk of liver disease. These include nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). NASH is a more advanced form of NAFLD.^1,2

However, it's important to note that BMI has many limitations. For example, it is not a direct measure of body fat. Therefore, while doctors use it as a tool to diagnose NASH, it is not the only factor in a diagnosis.⁷

Why does BMI matter for your liver health?

BMI can be helpful in assessing your overall liver health. A high BMI may indicate excess body fat. This excess fat can build up in the liver. Over time, this fat buildup can impact how your liver functions. Ultimately, it can result in NAFLD.^1,2

The liver is a vital organ. It performs many functions to keep you healthy. These tasks include:³

• Detoxifying the blood
• Making bile, which aids in digestion
• Storing glycogen and vitamins

If you leave NAFLD untreated, it can progress to NASH. With NASH, there is both fat buildup and inflammation and cell damage in the liver. This can lead to even more serious health issues, like cirrhosis (permanent scarring of the liver) and liver cancer.⁴

What is the ideal BMI to reduce NASH risk?

The higher your BMI, the greater your risk of developing NAFLD and NASH. A high BMI can also be linked to other health conditions, like type 2 diabetes, high cholesterol, and obesity. These conditions further increase the risk of developing liver complications.^1,2,5

You can find out your own BMI using an online calculator. According to the Centers for Disease Control and Prevention (CDC), BMI scores fall into the following categories:¹

• Less than 18.5 – underweight
• 18.5 to 24.9 – normal weight
• 25 to 29.9 – overweight
• 30 or above – obese

Generally, a BMI between 18.5 and 24.9 is considered the ideal range for reducing the risk of NAFLD and NASH. However, it is not just about the number. It is also important to maintain a healthy balance of muscle and fat.¹

When diagnosing NAFLD and NASH, doctors take many factors into account. They use your BMI as well as other health indicators to get a comprehensive view of your liver health. Other health indicators may include:^1,2,5

• Waist circumference
• Co-occurring health issues
• Certain lifestyle factors

Can you develop NAFLD without a high BMI?

While a high BMI is a risk factor for NAFLD and NASH, these conditions can occur in people who are not overweight. A person may have a healthy BMI and still develop NAFLD. This may be due to:⁵

• Genetics
• Hormones
• Lifestyle factors
• Body composition

Even with a healthy BMI, fat can still collect in the liver. Living a healthy lifestyle and getting regular checkups are crucial to maintaining optimal liver health.⁵

How can weight management and lifestyle changes help?

The first step in treating NAFLD and NASH is to lose weight. Research has shown that effective weight management is among the most effective ways to treat these conditions. Losing weight helps because it:^2,3,6

• Reduces fat in the liver
• Improves liver function
• Helps manage other risk factors, like diabetes and high cholesterol

Try these tips to maintain a healthy weight and support your weight management goals:⁶

• Eat a balanced diet
• Be mindful of portion sizes to avoid overeating
• Stay hydrated
• Exercise regularly
• Limit sugary and processed foods
• Stay active throughout the day
• Try to get 7 to 9 hours of quality sleep each night