IF YOU TIP the Toledos at a tenth of a ton or more, you have a new hefty heroine. She is Catherine McDermott, a woman of stout heart as well as ample proportions who has just won an important victory in the New York Court of Appeals. Eleven years ago, the Staten Island woman was turned down by the Xerox Company for a job because of obesity. Then 56 years old, she stood 5 feet 6 inches tall and weighed 249 pounds. Mrs. McDermott, who was widowed at an early age and raised five children alone, has plenty of energy and courage. Acting as her own attorney, she sued Xerox, and this week she won.

"The only thing wrong with me," she argued, "is that I don't look that great. But I could do my work, mind the kids, run a Brownie troop and teach in Sunday school even though I looked the way I looked." Deploring the fact that the rotund usually just roll over when they suffer job discrimination, she decided to fight back. She spent 10 years in court waging the battle. Xerox countered with arguments about the increased cost of life and health insurance for the overweight. But this week, the highest court of the state ruled that obesity is a physical "impairment" under the state's human rights laws. And just as an employer cannot refuse to hire a blind man for a job that does not require sight, he cannot turn down a fat woman for a job that doesn't require her, for some special reason, to be thin.

Xerox changed its policy soon after Mrs. McDermott filed her suit in 1974. Now other employers in New York State will have to conform to the court's ruling too. That makes sense. Mrs. McDermott is a computer systems analyst, not a steeplejack or an aerobics instructor, and she can probably do just as good a job at 249 as she would at 125. She sounds like a great person in spirit as well as girth.