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Excessive Fast-Food Intake Increases ALT Levels

Data indicate that a diet heavy in fast foods — even if consumed for a short period — can significantly increase ALT levels.

Intermittent elevations in liver enzymes among seemingly healthy individuals often go unexplained. In this study, Swedish investigators evaluated whether serum alanine aminotransferase levels and hepatic triglyceride content are affected by excessive intake of foods rich in saturated protein.

Eighteen healthy volunteers (mean age, 26; 12 men) were assigned to fast-food–based diets for 4 weeks with the goal of doubling baseline caloric intake and increasing body weight by 5% to 15%. Physical activity could not exceed 5000 steps daily, and alcohol consumption was maintained at baseline levels (1 patient did not drink alcohol, 1 drank 340 g weekly, and 16 drank <140 g weekly). Blood was drawn from all subjects at baseline, weekly during the study, and at 6-month follow-up. Hepatic steatosis was approximated using nuclear magnetic resonance spectroscopy. Age- and sex-matched controls were recruited to control for random ALT fluctuations that are induced naturally by food intake. One subject was lost to follow-up.

During the study period, mean ALT levels increased significantly (from 22.1 U/L to 69.3 U/L), as did weight (from 67.6 kg to 74 kg), body-mass index (from 21.9 to 23.9 kg/m²), waist circumference (from 76.4 cm to 83.1 cm), hip circumference (from 86.5 cm to 90.4 cm), percentage of body fat (from 20.1% to 23.8%), and insulin resistance (from 0.89 to 1.6, according to the homeostasis model assessment). Overall, 14 of 18 participants developed abnormal ALT levels within the first week. However, only two participants fulfilled criteria for hepatic steatosis. All participants’ ALT levels returned to normal within several weeks after stopping the fast-food diet. Fat intake was unrelated to ALT elevations, but, by week 3 of the diet, sugar and carbohydrate intake correlated with rising ALT levels. The control group’s ALT levels did not change during the study.

Comment: This clever study, although small in size, demonstrates that a fast-food–type diet — even if consumed for a brief period — can significantly increase ALT levels. Interestingly, most of the participants displayed rising ALT levels within 1 week of starting the diet, which suggests that fatty infiltration is unlikely to be the cause of the observed ALT elevations (substantial increase of lipids within hepatocytes does not occur so quickly). In fact, only two participants fulfilled criteria for hepatic steatosis at the end of the study. The authors postulate that the elevated ALT levels could have been the result of a sudden increase in metabolic substrates to the liver, which caused an enzymatic induction in hepatocytes and normal leakage of ALT through the cell membrane. Because an over-indulgent diet can significantly increase liver-enzyme levels, clinicians evaluating patients with elevated ALT levels should ask questions not only about alcohol intake but also about excessive food intake.

— Atif Zaman, MD, MPH

Published in Journal Watch Gastroenterology February 14, 2008

Citation(s):

Kechagias S et al. Fast-food based hyper-alimentation can induce rapid and profound elevation of serum alanine aminotransferase in healthy subjects. Gut 2008 Feb 14; [e-pub ahead of print]. (http://dx.doi.org/10.1136/gut.2007.131797)

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