Michel Guérard, a driving force behind the 1960s culinary movement known as nouvelle cuisine and the creator of the enormously influential “slimming cuisine” at his 19th-century spa in Eugénie-les-Bains, France, died at his home there. He was 91.

His daughters, Eléonore and Adeline, said that he died overnight between Sunday and Monday.

Mr. Guérard was already recognized as one of the most daring and innovative chefs in France, in 1974, when he took over Les Prés d’Eugénie, one of the smaller, less developed properties in a chain owned by the family of his wife, Christine. Together, the couple turned the spa into a major tourist destination, despite its remote location in southwestern France, in large part because of what Mr. Guérard called “cuisine minceur,” a low-fat, no-starch, no-sugar, low-calorie application of nouvelle cuisine. (Guests could also go for the full-fat, lavish experience on the other half of the menu if they liked.)

His own efforts to lose weight at the spa, and his disgust with traditional diet dishes, inspired him to develop dishes that relied on vegetable purées combined with low-calorie fromage blanc for sauce, rather than butter and cream. Rather than sautéing in oil or butter, he steamed fish and meats in sealed containers with herbs to infuse and retain flavor.

He regarded traditional spa cuisine, which was imposed on him when he first visited Eugénie and needed to lose 15 pounds, as additional pain for patients already struggling with the rigors of weight-loss regimens. “The punishment was too severe to be borne,” he wrote in “Michel Guérard’s Cuisine Minceur” (1976), “evasive action had to be taken.”

To put pleasure back into the equation, he created dishes like mousseline of crayfish with watercress sauce, leg of milk-fed lamb cooked in wild hay, and a 60-calorie pear soufflé “as light and fragrant as hickory smoke,” in the words of the Washington Post food writer William Rice.