A diet plan as old as the Dead Sea Scrolls is at the heart of a weight-loss craze. It's making new headlines because actor Chris Pratt posted an Instagram story about how he is following it.

In the now-expired Instagram post, Pratt describe the diet as “21 days of prayer and fasting,” according to Time. But the plan is a little more detailed than that.

The Daniel Plan — developed by Rick Warren, author of the best-selling book “The Purpose Driven Life” (see his TED Talks video below) and pastor of a Southern California mega-church — is an age-old combination of healthier eating and exercise. Warren developed the plan for himself and his church members with the help of celebrity doctors and authors Mark Hyman, Daniel Amen and Mehmet Oz (the Dr. Oz of television fame).

The plan has roots in the biblical story of Daniel from the Old Testament. In the story, Daniel abandoned the king's rich food and fasted, eating only simple foods like vegetables and drinking water in order to honor God.

On the Daniel Plan website, the stress is put on faith.

"God can make changes in your life that you have never dared to even dream of. He specializes in miracle makeovers. Think about this: what positive changes in your life could happen if you relied on God's unlimited power instead of your limited will power."

The diet details

The 21-day diet emphasizes eating fresh, organic and unprocessed foods. Meals are heavy on fruits and vegetables and light on meat. The eating plan, drafted by Hyman, also emphasizes coldwater fish — wild salmon, halibut, black cod — that are rich in omega-3 essential fatty acids.

Hyman’s plan names several foods — or processed food ingredients — to avoid forever. Most of the ingredients are part of highly processed foods common on grocery store shelves. Among the items to avoid are high-fructose corn syrup, trans fats, artificial sweeteners and fat substitutes such as Olean.

“I always say, ‘If it’s made in a plant, you probably shouldn’t eat it’,” Hyman tells Warren in an online video interview. “If it’s grown on a plant, it’s OK to eat it.”

Foods to embrace, according to the Daniel Plan, include:

  • omega-3 eggs, up to eight a week
  • legumes such as lentils and chickpeas
  • slow-burning, low-glycemic vegetables such as broccoli, kale and spinach
  • berries, cherries, peaches, plums, pears and apples
  • organic, chemical-free poultry
  • organic, grass-fed beef or lamb, but no more than four to six ounces once or twice a week.

As with most weight-loss plans, exercise is also a component of the Daniel Plan. The emphasis starting out is on choosing an exercise you enjoy and then to increase training slowly. From there, the focus is on interval training.

Group support is also a key component of the Daniel Plan. Bible study groups have become Bible study and exercise groups. Studies indicate that people who try to lose weight or adopt healthier habits in groups are more likely to be successful than individuals working independently, according to Warren’s blog.

Safety and effectiveness

Group support is helpful for sticking with any diet plan, says Marisa Moore, a registered dietician in Atlanta and member of the Academy of Nutrition and Dietetics.

The plant-based diet of the Daniel Plan “can be a good plan — as long as you get all the nutrients you need,” Moore said, adding that sometimes those who switch to a vegetarian diet fall short of getting critical nutrients.

Richard Bloomer, dean of the University of Memphis’ School of Health Studies, has conducted several small studies on the Daniel Fast. According to Time, Bloomer's research has shown that the diet can begin to lower risk factors for heart disease, such as high blood pressure and cholesterol, just after three weeks.

“It just shows, I think, the power of food,” Bloomer says. “There’s a lot of potential health benefits from adopting this approach.”

Editor's note: This story was originally published in February 2012 and has been updated with new information.

What is the Daniel (diet) Plan?
A diet plan as old as the Dead Sea Scrolls is at the heart of a weight-loss craze.