At the end of the shorter trial, the male rats with 12-hour access to HFCS had gained significantly more weight than the group given access to sucrose—even though they actually consumed fewer calories in liquid form (the sucrose group ate enough chow to make up for the difference). That seems pretty important until you look at some of the details: the 24-hour HFCS group consumed roughly the same number of calories, on average, as their 12-hour peers, but didn't put on the same amount of weight. In fact, the 24-hour group wasn't significantly different (in the statistical sense) than either the sucrose or chow-only controls.
The longer-term study could have clarified exactly what was going on here, but the authors eliminated the sucrose group, "Since we did not see effects of sucrose on body weight in Experiment 1." In this experiment, the 24-hour group actually gained more weight than the control population as early as three weeks into the experiment. In fact, they gained more weight than the 12-hour group, although this difference isn't statistically significant. It doesn't appear that the authors attempted to explain why the two experiments seem to have produced different results.
At the end of this study, the fat pads were dissected out and weighed, and the abdominal fat pads of the 12-hour group were significantly different from those of the chow-only control. However, the abdominal fat of the 24-hour group (which, remember, gained more weight) wasn't significantly heavier than the control group.
To confuse matters further, the authors also ran a group of females through the long-term study protocol, and this time included a group with access to a sucrose solution. Females gained less weight in general than males, and those with 12-hour access to either HFCS or sucrose solutions finished the experiment in a statistical dead heat. Only the 24-hour HFCS group showed a significant increase in weight gain (and had a corresponding increase in fat deposition).
