Fast food (FF) consumption is highly prevalent and associated with high caloric intake and a greater risk of diabetes. Little is known about the impact of fast food consumption on NAFLD risk in healthy adults or whether the effect of fast food on steatosis is different among persons with metabolic risk factors, including obesity and diabetes.
A new study from Keck Medicine of USC motivates people to reduce fast-food consumption. The study found that eating fast food is associated with nonalcoholic fatty liver disease, a potentially life-threatening condition in which fat builds up in the liver.
The amount of fat in the liver is significantly higher in obese or diabetic individuals who consume 20% or more of their daily calories from fast food than in individuals who consume less or no fast food, according to research. And when fast food accounts for at least one-fifth of their diet, the general population experiences mild increases in liver fat.
Ani Kardashian, MD, a hepatologist with Keck Medicine and lead author of the study, said, “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. 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 previous research has shown a link between fast food and obesity and diabetes, this is one of the first studies to demonstrate the negative impact of fast food on liver health.”
“The findings also reveal that a relatively modest amount of fast food, which is high in carbohydrates and fat, can hurt the liver. If people eat one meal a day at a fast-food restaurant, they may think they aren’t harming. However, if that one meal equals at least one-fifth of their daily calories, they are putting their livers at risk.”
To ascertain the effect of fast-food consumption on liver steatosis, researchers used the most recent data from the country’s largest yearly nutritional survey, the 2017-2018 National Health and Nutrition Examination Survey.
The study defined fast food as meals—including pizza—from establishments with drive-through lanes or no wait staff.
The researchers reviewed about 4,000 people’s fatty liver measurements from the survey and then correlated these readings to the subjects’ fast-food intake.
52% of those respondents admitted to eating some fast food. Of these, 29% obtained at least a quarter of their daily caloric intake from fast food. Only 29% of survey participants saw their liver fat levels rise.
Even after data were corrected for several additional characteristics such as age, sex, race, ethnicity, alcohol consumption, and physical activity, the connection between liver steatosis and a 20% diet of fast food remained the same for both the general population and those with obesity or diabetes.
Kardashian said, “Our findings are particularly alarming as fast-food consumption has increased in the last 50 years, regardless of socioeconomic status. 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.”
“The study will encourage health care providers to offer patients more nutrition education, especially those with obesity or diabetes who are at higher risk of developing a fatty liver from fast food. The only way to treat liver steatosis is through an improved diet.”