If eating your favourite cheeseburger, french fries, and other high-fat foods wasn’t bad enough, combining it with your favorite soda just makes it worse, according to new research, which found that a high-sugar, high-fat Western diet is more damaging than a diet high in saturated fats alone.

The study, published in Experimental Physiology, shows that mice fed a high-fructose, high-fat Western diet, even for a short amount of time, suffer more liver damage than when they are fed a solely high-fat diet. While natural fructose found in fruits like berries, raw apples, and sugar cane can actually increase their nutritional value, artificial fructose, found in most sweeteners, sodas, and artificial juices, have gained lots of attention lately for their health risks.

Previous studies have already shown a link between fructose consumption and a rise in obesity rates. The current study now shows that combining it with fatty foods can damage the liver. "This result points to the harmful effect of adding fructose to the usual Western, high-fat diet and, together with other related findings, should stimulate the discussion on the use of fructose and fructose-containing sweeteners in beverages and packaged foods," said Dr. Susanna Iossa, who led the study at the University of Naples, Italy, in a press release.

"We performed the research by using an animal model of adult sedentary humans, consisting of adult rats, that were fed for two weeks with either a low-fat diet, a high-fat diet or a diet rich in fat and fructose. This latter diet is very similar in composition to the diet consumed by the large majority of the Western population. After the diet period, we evaluated liver function and we found that the presence of fructose in the high-fat diet exacerbated the impairment of this important metabolic organ, by increasing the build-up of fat in the liver, and decreasing liver insulin sensitivity.”

But why did manufacturers switch from using glucose or sucrose, which are more easily metabolized in the body, to fructose? In an effort to save money, many of them went with sugar made from one of the most abundant crops in the U.S. — corn. High-fructose corn syrup, which is present in most sweets and soft drinks, is known to affect glucose metabolism in mice, causing diabetes. Other studies have shown the detrimental effects that fructose consumption has on children, suggesting that it might lead to cardiovascular disease and cancer.

With new evidence suggesting that most soft drinks contain more fructose than the amount labeled, there is no telling how much damage has already been done. As Dr. Iossa concluded, "Much more research should be undertaken in the future, especially regarding the impact of the high-fat, high-fructose diet on other metabolically important organs, in order to establish the real impact of this unhealthy dietary habit on health and well-being."

So, the next time you crave some chili dogs, skip the soda, and down a good ol' cup of water.

Source: Iossa S, Crescenzo R, Bianco F, et al. Fructose supplementation worsens the deleterious effects of short term high fat feeding on hepatic steatosis and lipid metabolism in adult rats. Experimental Psychology. 2014.