LOS ANGELES — The occasional Big Mac or Whopper can be delicious, but new research is warning fast food fans to keep those visits to the drive-thru sporadic at best. Even if you are trying to eat the healthiest fast food items, a new study finds that fast food can lead to nonalcoholic fatty liver disease. That condition, which sees fat build up in the liver, can be fatal.
Scientists at the University of Southern California report individuals who are obese or diabetic and get more than 20 percent of their daily calories from fast food display “severely elevated” fat levels in their livers compared to others who eat less or no fast food. Moreover, they note that among the general population, if more than a fifth of a person’s diet consists of fast food, it will increase fat levels in their liver.
“Healthy livers contain a small amount of fat, usually less than 5%, and even a moderate increase in fat can lead to nonalcoholic fatty liver disease,” says Ani Kardashian, MD, a hepatologist with Keck Medicine and lead author of the study, in a university release. “The severe rise in liver fat in those with obesity or diabetes is especially striking, and probably due to the fact that these conditions cause a greater susceptibility for fat to build up in the liver.”
While this isn’t the first study to suggest a link connecting fast food with obesity and diabetes, this is one of the first projects to showcase the negative impact of fast food on liver health specifically. Notably, the study also found that even just modest amounts of high-carb, high-fat fast food can hurt the liver.
“If people eat one meal a day at a fast-food restaurant, they may think they aren’t doing harm,” Dr. Kardashian explains. “However, if that one meal equals at least one-fifth of their daily calories, they are putting their livers at risk.”
3 in 10 Americans have a fatty liver
Nonalcoholic fatty liver disease, also called liver steatosis, can lead to cirrhosis (scarring of the liver), which can in some cases eventually cause liver cancer or failure. Liver steatosis affects over 30 percent of the U.S. population.
Study authors analyzed the most recent available data from the nation’s largest annual nutritional survey: The 2017-2018 National Health and Nutrition Examination Survey. This approach allowed them to determine the impact of fast food consumption on liver steatosis.
For the purposes of the study, the team characterized fast food as meals, including pizza, from either a drive-through restaurant or an eatery without a wait staff. They evaluated the fatty liver measurements of roughly 4,000 adults and then compared their responses regarding fast food habits. Among those surveyed, 52 percent reported eating some fast food. Within that group, 29 percent consumed one-fifth or more of their daily calories from fast food. Notably, only that 29 percent experienced an increase in liver fat levels.
This association remained intact for both the general population and those with obesity or diabetes even after researchers accounted for various additional factors like sex, race, age, ethnicity, alcohol use, and physical activity levels.
“Our findings are particularly alarming as fast-food consumption has gone up in the last 50 years, regardless of socioeconomic status,” Dr. Kardashian concludes. “We’ve also seen a substantial surge in fast-food dining during the COVID-19 pandemic, which is probably related to the decline in full-service restaurant dining and rising rates of food insecurity. We worry that the number of those with fatty livers has gone up even more since the time of the survey.”
Study authors hope their work encourages more doctors and health care providers to educate their patients when it comes to nutrition. As of today, the only way to treat liver steatosis is by switching to a healthy diet.
The study is published in the journal Clinical Gastroenterology and Hepatology.