Health Secretary Robert F. Kennedy Jr. announced Wednesday that his department had issued new “guidance on sex-based definitions” aimed, in part, at keeping transgender women and girls out of female sports and fulfilling President Trump’s pledge that the federal government will recognize only two sexes: male and female.

“This administration is bringing back common sense and restoring biological truth to the federal government,” Mr. Kennedy said in a statement. “The prior administration’s policy of trying to engineer gender ideology into every aspect of public life is over.”

As part of the initiative, the Health and Human Services Department has launched a new web page for the federal Office on Women’s Health. The page, entitled “Protecting Women and Children,” features a video with Riley Gaines, the former University of Kentucky all-American swimmer who says she was put at a competitive disadvantage when competing against a transgender woman.

The guidance offers detailed definitions for the words “male” — “a person of the sex characterized by a reproductive system with the biological function of producing sperm” — and “female” — “a person of the sex characterized by a reproductive system with the biological function of producing eggs (ova).”

The announcement came in response to an executive order Mr. Trump issued on Jan. 20 that gave the health department 30 days to issue “clear guidance” to the public on how to interpret sex-based definitions. “These sexes are not changeable and are grounded in fundamental and incontrovertible reality,” the order declared.

On Tuesday, Mr. Kennedy delivered a welcome address to department employees in which he said his agency would work toward helping Americans “to discover our own paths to living our fullest lives, unleashing the potential in every one of us to make good personal choices that allow us to nourish, to heal and to develop ourselves.”