Fatty liver (also known as steatosis) is the accumulation of fat in liver cells. It has been associated with alcohol use, weight gain, and diabetes. The weight of the liver can be approximated by ultrasound and an increase of 5% of more is considered to be fatty. Liver enzymes, measured by a blood test, are also elevated.
In one study, 90% of morbidly obese patients had abnormalities of the liver. 30% had fatty liver. The accumulation of fat alone is unlikely to cause any noticeable change in one’s health; only one fifth of these patients had liver-related complaints (such as pain, yellow discoloration, or fatigue). The good news is that weight loss by low-calorie dieting, or starvation is accompanied by improvement in fatty change and return of liver function tests to normal (Gastroenterol Clin North Am 1987. Fatty liver disease in morbid obesity. Jun;16(2):239-52)
Another study showed that fatty liver was much more common in male obese students (69%) than in female obese students (27%). Cholesterol, uric acid, and insulin were significantly higher in male obese students with fatty liver than in male obese students without fatty liver (Nippon Shokakibyo Gakkai Zasshi 1995. Fatty liver and obesity in university students. Oct;92(10):1743-51).
One year after losing weight, a group of people with fatty liver showed dramatic improvement in the two most commonly used liver tests (AST and ALT), nearly all down to within normal levels. AST dropped from an average of 74 to 25. ALT also dropped from 109 to 30. A comparable group that did not lose weight showed higher AST and ALT levels on follow-up visit than in their initial visit. (J Korean Med Sci 1995. Effect of weight control on hepatic abnormalities in obese patients with fatty liver. Dec;10(6):414-21)
Finally, one study did find that people with fatty liver were less likely to get into ketosis and don’t lose weight as rapidly (Internal Medicine 1992 Aug;31(8):978-83).