GPT and obesity due to melanocortin 4 receptor deficiency: Another interesting study by Tsai et al. [17] showed a good correlation between obesity, alcohol consumption, and liver enzyme functions using NHANES data for a 3-year period (2005–08) from more than 8300 adults with ages > 20 years as sample size found that obese females who are excess drinkers tend to have an increased AST, ALT, and GGT levels compared to nonobese and nondrinker females.