Sugar overload can damage the heart:

http://www.sciencedaily.com/releases/2013/06/130614165135.htm

The glucose metabolite glucose 6-phosphate (G6P), causes stress to the heart that changes the muscle proteins and induces poor pump function leading to heart failure… G6P can accumulate from eating too much starch and/or sugar. [thank you editors for clarifying that indeed STARCH to can be a serious problem, not JUST that which tastes sweet!]

"When the heart muscle is already stressed from high blood pressure or other diseases, and then takes in too much glucose, it adds insult to injury," Taegtmeyer said.

The study has opened doors to possible new treatments. Two drugs, rapamycin (an immunosuppressant) and metformin (a diabetes medication) disrupt signaling of G6P and improved cardiac power in small animal studies.

"These drugs have a potential for treatment and this has now cleared a path to future studies with patients," Taegtmeyer said.