Scientists who were working to find out how diet affects the operation of the liver put 14 overweight people on either a low-carbohydrate or low-calorie diet.

They found those eating fewer carbs lost almost double the weight over two weeks, and several changes in liver function were identified as part of the reason why.

An assistant professor at the UT Southwestern Medical Centre in Dallas, Dr Jeffrey Browning, said, ''Energy production is expensive for the liver.''

The average weight loss for the low-calorie dieters was about 2.2kg, while the low-carb dieters lost about 4.3kg on average.

Dr Browning said the study highlighted how diet could cause a ''dramatic change'' in where and how the liver was producing glucose, a form of sugar.

Test subjects on the low-calorie diets received about 40 per cent of their glucose from a substance called ''glycogen'', which is made from ingested carbohydrates stored in the liver until needed.

Those on low-carb diets, however, sourced only 20 per cent of their glucose from glycogen.

They burned more fat instead of dipping into their reserves.

Dr Browning said the findings offered new hope for targeted non-drug-related treatments for obesity and also liver-related disorders such as diabetes, insulin resistance and non-alcoholic fatty liver disease.

''Instead of looking at drugs to combat obesity and the diseases that stem from it, maybe optimising diet can not only manage and treat these diseases, but also prevent them,'' Dr Browning said.

''Understanding how the liver makes glucose under different dietary conditions may help us better regulate metabolic disorders with diet.''

The findings are published in the journal, Hepatology. AAP