Not "overweight." At 132 pounds, Yasuda is the ideal size for luging. It's her equipment that weighs too much.
Because of a miscalculation, Yasuda brought too much ballast with her to weigh-ins for Tuesday's competition. Lugers are allowed 13.1 kg of "additional weight." Yasuda brought 13.3.
Though there is no weight requirement for luge, women who weigh less than 75 kg (Yasuda weighs roughly 60 kg) may make up 75 percent of that difference without going over the limit. Yasuda exceeded that limit by less than half a pound.
Though Yasuda was not expected to be a medal contender, this would have been her first Olympics. It's unfortunate that the equivalent of the weight of a cheeseburger would keep her from competing, especially when it's the result of accidentally miscalculating a somewhat complex formula. But those are the rules. The IOC has to draw the line somewhere, and a small technicality can mean an athlete can't compete.