On Aug. 9, 2010, White House chef Sam Kass holds a plate of seafood from the Gulf of Mexico that had been prepared at the White House by members of the New Orleans Saints football team. (Pablo Martinez Monsivais/AP)

Sam Kass, a White House chef and leader of the first lady’s healthy-eating campaign, is stepping down at the end of the month.

Kass, who recently married, is moving to join his wife, the television journalist Alex Wagner, in New York. Kass’s departure will be felt both on Washington’s social scene and within the White House, where his deep ties to the Obama family made him a high-profile figure during his six years here.

He became a regular presence in Washington’s top restaurants; often, a visit from Kass preceded a coveted dinner reservation from Michelle Obama. Behind the scenes in the first lady’s office, Kass largely shaped her efforts to reduce childhood obesity. He was also a part of daily life for the first family and until recently prepared their nightly dinners.

President Obama, who attended Kass’s wedding this summer, said in a statement Monday that Kass had “grown from a close friend to a critical member of my team.” The friendship gave Kass rare access and influence beyond his titles: He vacationed with the Obama family, is one of Barack Obama’s golfing buddies and may be the only man who can boast that a sitting president was a guest at his bachelor party.

Kass, 34, has similarly been a confidant of the first lady and dogged promoter of her Let’s Move campaign, which the president also praised.

This April 2 file photo shows first lady Michelle Obama and Sam Kass walking towards the White House Kitchen Garden to plant vegetables with local students at the White House in Washington. (Susan Walsh/AP)

“From constructing our kitchen garden to brewing our own honey brown ale, Sam has left an indelible mark on the White House,” Obama said. “And with the work he has done to inspire families and children across this country to lead healthier lives, Sam has made a real difference for our next generation.”

The move from chef into food policy was a leap for Kass, who sometimes found the impasses between major food corporations and anti-obesity activists frustrating. Before coming to Washington with the Obamas, he had traveled the world cooking and has said it was then he began thinking about the lack of attention paid to nutrition. But he was relatively unknown among nutrition advocates.

Marion Nestle, an author and professor of nutrition, food studies and public health at New York University, recalled meeting Kass on his 30th birthday. “I remember thinking at the time, ‘He’s just a kid. What is he doing with food and nutrition policy?’ ”

The president later named Kass the first White House senior policy adviser on nutrition, and Michelle Obama gave him an outsize role in directing her signature issue.

Nestle may have thought Kass was green when he started, but she changed her mind over the years. He became “far more sophisticated politically,” she said in an interview.

She admired his promotion of local produce using the White House garden and his efforts organizing advocacy around the nutrition guidelines for the National School Lunch and National School Breakfast programs.

Michelle Obama also credited Kass — who was a presence at her side during nearly all of her healthy-eating events — with helping to bring more nutritious options to grocery stores and working to improve the way healthy foods are marketed to children. Kass positioned the first lady and her office as a kind of middleman between nutrition advocates and the food industry, which have long been at odds.

In this video from 2012, White House chef Sam Kass and sous chef Tafari Campbell brew batches of ale and porter with honey supplied by the White House beehive. Kass, who also served as the leader of Michelle Obama's "Let's Move" initiative, is leaving his post at the end of the month. (whitehouse.gov)

Scott DeFife, executive vice president for policy and government affairs for the National Restaurant Association, described his working relationship with Kass and the administration as “collaborative and cooperative.” The association’s conversations with Kass and the White House, in part, led to the launch of Kids LiveWell, an initiative in which more than 42,000 restaurants began to offer healthy menu options to children.

Geoff Tracy, owner of the Chef Geoff’s chain and the chairman of the Restaurant Association Metropolitan Washington, said Kass’s influence pushed local restaurants to make similar changes. “I certainly have revamped our kids’ menu,” he said. “That movement started with the White House.”

Still, the White House’s decision to partner with industry was often criticized by Nestle and other advocates who saw some of those efforts as allowing corporations to score public relations points alongside the first lady without substantially changing the nation’s food landscape.

Kass leaves as some of the progress the White House has claimed on food policy is being threatened. The administration’s overhaul of school nutrition standards — led by the first lady’s office and Kass — has been opposed by congressional Republicans who want to make the standards less restrictive. And it’s unpopular among schoolchildren, some of whom have taken to social media to blame the first lady for their unappealing lunches.

The administration will also soon begin to implement changes to the Nutrition Facts labeling, an issue that will come under heavy scrutiny from food companies and their high-dollar lobbyists.

Kass was hired by the Obamas in 2005 to be the family’s personal chef when Barack Obama was elected to the Senate. The young chef had known Michelle Obama since he was a teenager through neighborhood circles in the Hyde Park neighborhood; he then became a close friend of the family and a big-brother figure to Sasha and Malia Obama. His conversations with Michelle Obama in her Chicago home were the impetus for her to plant a vegetable garden on the South Lawn of the White House.

In a statement, she called him “an integral part of Let’s Move! from its very beginning — from discussions about children’s health around my kitchen table in Chicago, to setting the strategic vision of a national campaign in the White House, to spearheading efforts with the private sector across the country. Sam leaves an extraordinary legacy of progress.”

Kass will remain involved with the first lady’s healthy-eating program. He told the Wall Street Journal, which first reported his departure, that he will take a position in the private sector promoting healthy eating. He’s sure to remain a prominent figure within the food movement, giving speeches and presenting at conferences.

And his celebrity cachet stretches beyond those circles. This year, Vogue gave the title of “politics’ it couple” to Kass and Wagner, who hosts a daytime MSNBC news program.

“I love this family and believe in the work that we’re doing and the mission of the president and the first lady,” Kass told the Journal in an interview Sunday. “But after being recently married, I have to put our future first.”