The findings showed that liver fat levels dropped by up to 48 per cent after eating high-protein diet regardless of whether it came from a plant or animal source, and also prevented the occurrence of non-alcoholic fatty liver disease -- a very common disorder where excess fat accumulates in the liver -- especially in people with diabetes.

"When left untreated, fatty liver is an important step progress to Type 2 diabetes and can develop into liver cirrhosis, which can have life-threatening effects," said lead author Andreas F.H. Pfeiffer, Endocrinologist at the German Institute of Human Nutrition Potsdam-Rehbruecke (DifE), in Germany. 

Further, the study showed that high-protein diet caused favourable changes in the liver and lipid metabolism, improved insulin sensitivity and led to a significant reduction in the hormone fibroblast growth factor 21 in the blood.

For the study, the researchers investigated the effects of two high-protein diets -- plant- or animal-based -- on the metabolism of 37 female and male subjects between the ages of 49 and 78 years suffering from Type 2 diabetes and, in most cases, from fatty liver. 

The main source for the plant protein group were foods such as noodles or bread that were enriched with pea protein. The animal protein group consumed lean milk products as well as white meat and fish as protein sources.

The results showed that no negative effect was observed on renal function or glucose metabolism and all study participants benefited from the high-protein diet. 

The liver fat content decreased significantly, in half of the study participants by more than 50 per cent. 

The study was published in the journal Gastroenterology.