The antonyms for "gat fat" are "slender," "thin," "skinny," "underweight," and "lean." These words are used to describe someone who is physically fit and has a healthy body weight. Being slim or slender is considered attractive, and many people strive to maintain a healthy weight for both aesthetic and health reasons. Conversely, having too much fat can lead to obesity, which increases the risk of various health problems. Therefore, it's essential to maintain a healthy lifestyle, eat a balanced diet and engage in regular physical activity to stay healthy and avoid becoming overweight.