Milan, Italy (CNN) Hard on the heels of one of his first public comments since leaving office, President Barack Obama is heading overseas to talk about food.

Where else but Italy? The gastronomic heart of the world, Italy is a place where food is taken seriously, and its status as a culinary destination gives it the gravitas and credibility to be among the first to raise questions about the future of nutrition.

To be sure, Obama will have dined well. To fail to do that, even in Milan, the once industrial capital of the north now better known for its fashionistas, would be a crime, but that's not the meat of visit. It's far more somber and serious, to help advance sustainable food supplies for us all and generations to come.

Fresh in office in 2009, Obama initiated his "Feed the Future" campaign that by some accounts has helped 9 million farmers and more than 17 million children , many under 5 years of age, have a chance of improved nutrition in more than 19 countries worldwide.

At the same time, his wife Michelle planted the modest White House kitchen garden -- the creation of another First Lady, Eleanor Roosevelt -- and turned it into a source of nutritional food for her family and others. She went on to champion the Healthy Hunger-Free Kids Act in 2010 , providing much needed healthy meals for schoolkids, an early Trump target in scything back the Obamas' legacy.

Both Barack and Michelle have had a thing about helping the needy get access to good food for a long time.

So why step back into the limelight now?

President Trump will go to Italy later this month to the culinary heaven known as Sicily. Food likely won't be on his mind -- it could be the toughest of all his stops in his first overseas excursion as commander in chief.

Trump will be attending the G7 leaders summit, where topics like migration and climate change will vie for attention in an agenda already dense with thorny issues like Syria, Russia, globalization and trade.

Obama adds his voice to "Seeds and Chips, " a summit that aims to advance his own cherished principles and stitch together food issues that for most people are scudding along below the radar yet stalk our very existence.

He'll deliver the keynote speech at the global gathering of government ministers, innovators, business leaders and experts "to face one of the greatest global challenges: climate change and the issues linked to food supply in an increasingly populated world with progressively scarce resources."

Obama will be challenging Trump's stated goal to collapse the By raising these issues,Obama will be challenging Trump's stated goal to collapse the COP21 climate change agreement forged in Paris -- perhaps Obama's biggest global legacy -- as well as point out Trump's hacks at his wife's signature legacy too.

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The United States was one of the last big polluters to come on board and accept the principle of climate change. Obama's desire to cut a deal in Paris determined neither China nor Russia had any room to back out.

The "Seeds and Chips" summit that Obama is opening is in its third year, and its organizers are looking to him to nail down its legacy as a force for good and change.

Obama won't have to open his mouth to do that, or for that matter butt ideological heads with Trump. His presence and legacy alone will convey both the dire prospects for climate change and the importance of planning and preparing sustainable food supplies.

Some forward-leaning climate scientists have been saying for years that polar ice melts and unusual weather changes are here to stay, that so much damage has already been done by industrialization that turning back the clock is not an option.

In his two and a half hours on stage, Obama will deliver the guiding speech setting the tone for the event and then take questions.

The former President has come well prepared -- his former senior food policy adviser and former chef Sam Kass will be there too.

Obama should have no trouble holding his own among the gathered experts. Often chided as "policy wonk in chief," intellectual discourse is his staple. Turning up the heat and bringing passion to a topic many already feel exhausted by will be his challenge.

What ever sage advice he brings to the table, it won't be to Trump's taste. An avowedly anti-science instinct has led the current President to appoint an EPA chief, Scott Pruitt, who questions the majority-held scientific views on climate change and intends to roll back the hard-earned climate gains of Obama's administration.

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Obama, now out of office, seems unwilling to sit silently in the margins, like some Victorian schoolchild only to speak when spoken to.

Silence has been the default state for many previous Presidents happy to shed the responsibilities of the White House. But Trump's targeting of Obama's legacy -- his health care plan at home and climate change overseas -- seems to have pushed him to take up speaking engagements he knows will needle the new commander in chief.

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It's becoming increasingly clear that Trump and Obama never saw eye to eye, even following their now famous hour-long White House meeting late last year when they came out all smiles and bonhomie. It emerges now that was the meeting when Obama warned Trump about hiring Michael Flynn , Trump's soon to be fired National Security Adviser.

Obama was right that Flynn would be trouble.

Today Trump may feel he needs to follow his gut and learn climate change for himself too.

What he thinks about Obama's return to the global spotlight will no doubt be revealed in his Tweets, where no amount of sugarcoating will hide his sentiment.

But this is only the beginning. Obama has more global speeches penciled in, including one in the UK, just two days before Trump's big G7 summit.