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(CNN) - One of this country's most famous pastors, Rick Warren, was in the middle of baptizing more than 800 people into the Christian faith, and as he lifted each body out of the water, he says he could not help thinking, 'Wow, everybody's fat!"
Warren knew he had a health problem, too. So with the help of some experts, he came up with, and co-authored, "The Daniel Plan: 40 Days to a Healthier Life," a road map to better living through five key factors: faith, food, fitness, focus, and friends.
"We have to redefine what community's all about," Warren said in an interview with CNN's "The Lead with Jake Tapper." "It's about relationships. It's not about the food itself."
"We have all of these efforts in our culture to get us to eat the wrong thing at the wrong time in the wrong way, and we just thought well, maybe we could use community to support each other," said Warren.
"The science shows that the way we change behavior is by working together in groups. That's what the science shows, for all sorts of conditions, diabetes, and so forth," said co-author Dr. Mark Hyman.
"The Daniel Plan" was not a weight loss program, "it was about the science of creating health. The weight loss was a side effect," said Hyman.
About 12,000 people joined the plan, supporting each other, and cooking, shopping, and exercising together, said Hyman.
"They were there when they had issues and troubles and struggles to support each other and get back on track. That's the power of community. The community was the medicine," said Hyman.
The book's title comes from the bible.
"Daniel was a young Jewish leader who, during the captivity of the Jewish nation (was) taken to Babylon. He was being tutored by King Nebuchadnezzar, the Babylonian king, and one of the perks of being in the king's house is you got to eat all his fine foods," said Warren. "Daniel said, 'I'm not going to eat what's popular, I'm going to eat what's healthy.'"
Daniel challenged the king to a contest, where Nebuchadnezzar ate all the junk food, and Daniel ate healthfully.
"He and his friends at the end of the contest, you could see such a difference in their countenance. They were far healthier in the radiance of their faces. The king had to admit, 'You're right, let's go your way,'" said Warren.
This diet was a success for Warren, until he lost his son. Matthew Warren, 27, committed suicide earlier this year. In the months that followed, a grief-stricken Warren regained a lot of the 65 lbs he had initially lost on this diet.
"It has been the most difficult year of my life. You don't get over something like that, you get through it," says Warren.
When his son died, Warren says he did not sleep for six months.
"Then people were bringing me all these foods," said Warren. "As soon as I kind of got through that grieving time, I went back on the Daniel plan, I've lost 30 of the 35 (pounds) and am back on the way down again," said Warren.
"Setbacks are part of the recovery," the pastor says.
Warren's son suffered from a borderline personality disorder. He purchased a gun online.
"I am in support of the fact that no mentally ill person should be able to get a gun," said Warren. "I'm grateful for the fact that actually in California, we have some of the most strict gun control laws in the nation, and I'm sure that kept Matthew alive, because for years, he tried to get a gun.
"But the bottom line is, even when it is illegal in the nation, or a state where it's extremely strict, you can always find somebody who is unethical who will eventually sell it to you, and that's what happened," said Warren.
The country needs to take a multifaceted approach – deal with violence in society, change its thinking on mental illness, and deal with gun issues, said Warren.