Antonyms for the phrase "took off weight" would be related to gaining or adding weight. Some of the words that could be used as antonyms are "put on weight," "gained weight," "increased weight," "packed on pounds," or "grew heavier." These words convey the opposite meaning of losing weight, which is what "took off weight" depicts. Other antonyms could include "bulk up," "beef up," "fatten up," and "plump up," suggesting an increase in body mass or size. However, it's important to note that weight gain can be healthy and necessary for some individuals, whereas losing weight might be the goal for others.