The former president also noted that the Paris agreement focused on damage to the environment from the energy sector, leaving the role of food production largely unaddressed. “We are actually seeing a continuing increase in emissions coming out of the agriculture sector,” he said, “and a lot of that has to do with changing diets around the world.”

He said that even as the developed world works to reduce its consumption of meat, developing nations are eating more meat. “This offers a huge opportunity for entrepreneurs, businesses, scientists and thought leaders to make progress in an area where we have not made as much progress,” he said.

Mr. Obama observed that most people do not think of food as a source of pollution. “Because food is so close to us and is part of our family and is part of what we do every single day, people, I think, are more resistant to the idea of government or bureaucrats telling them what to eat, how to eat and how to grow,” he said.

The powerful agriculture lobby in Washington, he said, can also hinder change. “Historically in the United States, the one area where Democrats and Republicans agree is on the agriculture committees, because the members usually come from agricultural states and they’re very good at joining across party lines to protect the interests of food producers,” Mr. Obama said. “It makes for a difficult political dynamic for us being able to shape rational policy.”

Mr. Kass asked his former boss to speak about the developing field of personalized health and the part food plays in it. Mr. Obama mentioned that his daughter Malia has a peanut allergy and is participating in a Stanford University program that tailors treatment to the individual.

“How that translates into people’s eating habits, we don’t yet know,” he said. “Because a lot of people don’t just eat for health — we eat because it tastes good, too.”

He then brought up the desserts offered at a dinner on Monday night at the Palazzo Clerici, which houses the Italian Institute for International Political Studies. “I can’t say all the desserts that were served were good for me,” he said. “Even if you had told me they weren’t good for me, I still would have eaten them because they were good.”