Onions, green tea and olive leaf extract can fight obesity and its related diseases such as heart disease, diabetes and fatty liver, even when a high-fat and high-carbohydrate diet is indulged in.
Prof Lindsay Brown, from the University of Southern Queensland, tested a range of foods on rats that were being fed an unhealthy diet high in sugar and fat.
He found certain foods helped prevent the growth of inflammatory cells in the animals' fat pads, located in the abdomen, which take fat from the blood stream and store it, reports the Daily Telegraph.
Rats being fed food such as onions, green tea, olive leaf extract, purple carrots and chia seeds had a decreased number of fat cells and lost weight by the end of the study, despite maintaining a poor diet overall.
The rodents were also found with improved liver and heart function.
Brown said that the key message of his research was that people should "eat better rather than eat less".
Onions and olive leaf extract contain a flavonoid called rutin - also found in apples, tea and red wine - that Brown found reversed or prevented metabolic changes in rats fed the high-sugar, high-fat diet.
The findings have been published in the Journal of Nutrition and the Current Pharmaceutical Biotechnology.