Agriculture Secretary Sonny Perdue is not shy about sharing his taste for chocolate milk.

“I wouldn’t be as big as I am today without chocolate milk,” Mr. Perdue told reporters in May 2017, while discussing his plan to relax Obama-era school lunch rules. It was one of his first days on the job.

This week, the United States Department of Agriculture announced its final plans to lower nutrition standards for grains, flavored milks and sodium in school cafeterias that were part of the Healthy, Hunger-Free Kids Act of 2010 and that Michelle Obama, the former first lady, had advocated.

The changes, all of which will go into effect by July, apply to school meals that qualify for at least some federal reimbursement. They may seem relatively minor on paper, but like many Trump administration moves to reverse Obama-era policies, they come with some controversy.

First, the grains: The Obama-era rules required that schools must serve entirely “whole grain-rich” foods, meaning that the product — whether it is pizza, pasta or hamburger buns — must contain at least 50 percent whole grains.