Olestra

1996-1999

“100% Satisfaction, 0% Guilt.” These fat-free chips contained the controversial additive Olestra. During the low-calorie craze of the 1990s, several kinds of low-calorie chips were launched, for what could be better than chips that don't make you fat? Olestra quickly lost its appeal due to unpleasant side effects; the body could not absorb the substance, which in larger amounts caused gastric cramps and diarrhea. Olestra and the chips became known for causing “anal leakage.”

Additional info:

Wikipedia - a decent article about this infamous substance

Fastcompany - The Chips That Sent Us Running To The Loo

Pringles Fat Free Chips Commercial from 1998: