Based on an analysis of health data from 4,000 adults whose fatty liver measurements were included in the most recent National Health and Nutrition Examination Survey (from 2017–18), scientists discovered that people with obesity or diabetes who take in one-fifth or more of their daily calories from fast food have severely elevated levels of fat in their liver compared with those who eat less or no fast food. A diet consisting of at least 20 percent fast food was also linked to moderate increases in liver fat among the general population.
Many People in the Study Ate Fast Food Daily
“We were surprised to find how damaging fast food can be to the liver, especially among people who have diabetes or obesity,” says lead study author Ani Kardashian, MD, a hepatologist with Keck Medicine of USC. “I think most people are probably not aware that eating fast foods and an unhealthy diet can cause liver problems. Fatty liver is a major public health problem, which can lead to cirrhosis [the development of scar tissue in the liver], liver failure, and liver cancer.” Nonalcoholic fatty liver disease (NAFLD), also known as liver steatosis, is a condition in which excess fat builds up in the liver; it is not associated with alcohol use. The National Institute of Diabetes and Digestive and Kidney Diseases estimates that about one-quarter of U.S. adults have NAFLD. The condition is more common in those who have obesity or type 2 diabetes. More than half of those surveyed in this study consumed some fast food, and of these, 29 percent got one-fifth or more of their daily calories from fast food. A rise in liver fat levels was only observed in the latter group.
Why Are People With Diabetes or Obesity More Vulnerable to Liver Disease?
Dr. Kardashian explains that consuming large amounts of saturated fats and processed sweeteners, the hallmark of fast food, predisposes the body to accumulate fat in the liver. This effect is exacerbated in people with insulin resistance, a hallmark of prediabetes and type 2 diabetes, which causes abnormal amounts of excess fat to deposit in the liver. “This is probably why people with diabetes and obesity are particularly susceptible to the negative impacts of fatty liver,” she says.
A Surge in Fast Food Dining Is Cause for Concern
The researchers called the findings especially alarming as fast-food consumption has gone up in the last 50 years, regardless of socioeconomic status. They also noted that fast-food dining surged during the COVID-19 pandemic and the number of those with fatty livers may have gone up even more since the time of the survey. “My hope is that this study encourages people to seek out more nutritious, healthy food options and provides information that clinicians can use to counsel their patients, particularly those with underlying metabolic risk factors, of the importance of avoiding foods that are high in fat, carbohydrates, and processed sugars to protect their liver,” says Kardashian. “At a policy level, public health efforts are needed to improve access to affordable, healthy, and nutritious food options across the U.S.” The study authors added that future research should focus on how healthy food interventions for people with metabolic conditions may reverse or improve fatty liver.
