They are traditionally days of complete abstinence in the Universal Church, the American bishops granted a relaxation:
On January 28, 1949, the United States bishops issued modified regulations on abstinence in America again, after receiving a ruling from the Sacred Congregation of the Council. Partial abstinence replaced complete abstinence for Ember Wednesdays, Ember Saturdays, and the Vigil of Pentecost. https://fatima.org/news-views/pasting-part-7-fasting-in-the-1900s-pre-vatican-ii/