Zion Williamson's new contract doesn't include a so-called "homework clause" like the deal that Kyler Murray signed with the Arizona Cardinals, but the New Orleans Pelicans did try to protect themselves to a degree in constructing his second contract.
Williamson's five-year/$192.85 million extension -- slated to kick in during the 2023-24 season -- does have language pertaining to the former No. 1 overall pick keeping his weight in check, per Christian Clark of NOLA.com:
"According to league sources, Williamson’s contract stipulates that he will have weigh-ins periodically throughout the entirety of his new deal. The sum of his weight and body fat percentage must be below 295. If it is not, the amount of guaranteed money in Williamson’s contract can be reduced."
When he's been on the court as a Pelican, Williamson has been excellent, as he averaged 25.7 points per game with 7.0 rebounds in 85 games. However, he's played in just 85 of a possible 246 games, including missing the entirety of the 2021-22 season with a right foot injury.