First off, Gary Taubes has a new article on the link between sugar (either refined or high fructose corn syrup) and obesity, diabetes, and, gulp, cancer. It is titled, "Is Sugar Toxic?" I know his next book is on the effects of sugar in the diet and this is a taste of his upcoming work.
Second, can an active (non-sedentary) person get heart disease from eating a diet of grains, fruits, vegetables, and very little meat? I don't know, but an article on Egyptian mummies with heart disease certainly raises the question.
In an obesity study on rats, a diet high in fat is compared with a diet similar to the high carb, junk food laden American diet. The junk food diet leads the rats to develop metabolic syndrome, whereas the high fat diet does not. True, these are rats, not humans, but the results are very interesting nonetheless.
A comprehensive review of "heart healthy diets" (low fat, high carb, and including psychological counseling) over the last several decades concludes that they "had little or no impact on the risk of coronary heart disease mortality or morbidity." The research was performed by the Cochrane Collaboration, a non-profit group that independently reviews medical research in a non-biased way. They do not accept monies from pharmaceutical companies or other entities with vested interests in the outcomes of research. They also review and rate research conducted by other researchers, and they are big proponents of evidence based medicine.