The effect on cholesterol is a shock, but when you find out what appears to be the reason for the liver problems you might not be surprised.
A Swedish study done on young healthy adults asked them to eat two fast food meals a day and avoid exercise. The goal was for the subject to gain weight on the diet.
Researchers said they wanted to try to figure out why high fat diets in France don't harm their consumers. (Of course, every woman's magazine in the world and most of the supposedly more serious publications and productions, have some kind of answer for that question that seem to be based on some kind of guess. These researchers also find a reason, but this report does not tell us enough to know if their conclusions are some kind of guess as well or based on sound science.)
The diets raised HDL, the good cholesterol, protecting the heart and arteries, but also raised an enzyme that showed the liver could be getting damaged (details in the linked report).
Two of the subjects started developing fatty liver, a precusor to diabetes. The researchers say the elevated liver enzymes and damage were caused by the sodas accompanying the meals, but this report doesn't say why they come to that conclusion.
More details at source AFP report "AFP:Fast-food binge harms liver, but boosts good cholesterol: study "
Sometimes Press Associations disappear their reports within a few weeks so I asked a friend to save this in Usenet and the article is saved here .
A medical site report examined the study and didn't mention their own misgivings in Medpage Today "Fast-Food Bender Can Convert to Liver Damage Swiftly".
As you can see they make a point of the liver damage happening rapidly, noting that even holiday binging could bring on elevated liver enzymes. They note that 11 of the 18 bingers saw "pathological" levels of elevated enzymes though most didn't have liver damage. The report also relates that the study participants were kept to 5000 steps a day. Strict, but I bet a lot of gamers would love being in the binging group.
They also inform us the researchers had the bingers continue to drink as they had before the experiment so the elevated liver enzymes probably were not due to alcohol consumption.
This report is much more precise than the AFP as you can imagine putting exacting data on liver enzymes and control groups etc, and then the writer almost chattily says:
Eleven of the 18 volunteers persistently showed ALT above reference limits indicating liver damage (women >19 U/L, men >30 U/L) during the intervention. These increases were linked to weight gain and especially higher sugar and carbohydrate intake, the researchers said.
Again leaving us in the dark as to why that assumption was made.
The Medpage article also played down the increase in good cholesterol, possibly because, as CBC News reports in "Fast-food diets hurt liver, but boost good cholesterol: study " the cholesterol study has not been published yet. (Peer review problems?). Or medical prejudices could be responsible for both lack of publishing and downplay.