well this is what Atkins says in his book (it was the closest thing I had on hand)

"Walter Willett was co-author of a 1993 report on the 85,095 women who were tracked in the Harvard Study, Women with a high intake of trans fats were one an a half times more likely to develop coronary heart disease than women with a low intake of those so-called "foods". Clearly this was not only due to the deleterious effects of eating junk food. For many people, the real shocker in this study was the statistic that women who ate the equivalent of four or more teaspoons of margarine per day had a sixty-six percent greater risk of heart disease than women who ate little or no margarine."

He goes on to explain what I said earlier, that trans fat increases levels of bad cholesterol and lowers good cholesterol.

So there you go ... a study, and a big one at that.