(Reuters) - Jeb Bush is eating like a caveman, and he has literally shrunk in size.
The former Florida governor, expected to seek the Republican presidential nomination in 2016, is on the popular Paleo diet, which is based on what are believed to be the eating habits of the Paleolithic hunters and gatherers.
For Paleo practitioners, lean meat and fruits and vegetables are in and processed foods, dairy products and sugary delights are out.
For Bush, the results have been noticeable. Late last year he was something of a pudgy doughboy with a full face and soft jawline. Today the 6-foot, 4-inch-tall Bush sports a more chiseled look. His campaign-in-waiting would not say how much he had lost, but he looks to have shed 20 or 30 pounds.
His son George P. Bush, the newly elected Texas land commissioner, talked Jeb and Jeb Bush Jr. into trying it, a source close to Bush said.
Jeb and George Bush through the years
On the hunt for the presidency, Jeb Bush adopts a 'caveman' diet
** FILE ** President George W. Bush, center, walks off the 18th hole with his brother, Florida Gov. Jeb Bush, right, and father, former President George Bush, left, at the Cape Arundel Golf Club in Kennebunkport, Maine, in this July 7, 2001 file picture. Could there be a third President Bush? The current chief said Wednesday May 10, 2006 that younger brother Jeb would make a great one, too, and has asked him about making a run. The first President Bush likes the idea as well. (AP Photo/J. Scott Applewhite)
President Bush, center, with former President George H.W. Bush, left, and Florida Gov. Jeb Bush, walk together after participating in the christening ceremony of the aircraft carrier George H.W. Bush in Newport News, Va., Saturday, Oct. 7, 2006. (AP Photo/Lawrence Jackson)
Florida Gov. Jeb Bush, left, listens as former President George H. W. Bush offers condolences to the Ford family during a news conference in remembrance of former President Gerald R. Ford at the Gasparilla Inn in Boca Grande, Fla., Wednesday, Dec. 27, 2006. (AP Photo/Armando Solares)
President Bush waves to the crowd with his wife, Laura, and brother Jeb Bush on Monday, Nov. 6, 2006, in Pensacola, Fla., where Bush was drumming up support for local Republican candidates. (AP Photo/Mari Darr~Welch)
President Bush, left, stands on stage with his brother Gov. Jeb Bush, right, at a campaign rally at Pensacola Civic Center, Monday, Nov. 6, 2006. in Pensacola, Fla. (AP Photo/Pablo Martinez Monsivais)
President Bush, left, spends a moment with his brother and Florida Gov. Jeb Bush, prior to the President's speech on Social Security at the Pensacola Junior College, Friday, March 18, 2005, in Pensacola, Fla. (AP Photo/Phil Coale)
President George Bush chats with brother Gov. Jeb Bush as they acknowledge cheering supporters at a fundraiser for the Republican Party of Florida at the Contemporary Resort at Disney World in Orlando, Florida, Friday, February 17, 2006. (Photo by Joe Burbank/Orlando Sentinel/MCT via Getty Images)
Texas Gov. George W. Bush, right, gestures as his brother Florida's governor-elect Jeb Bush looks on during a joint news conference in New Orleans Wednesday, Nov. 18, 1998. The Bush brothers are attending the Republican Governors Association meeting which runs through Friday. A flood of media requests to interview the Texas governor and the Florida governor-elect prompted the sons of former President Bush to schedule a news conference Wednesday. (AP Photo/Bill Haber)
Florida Gov. Jeb Bush, right, hugs his brother, President Bush, left, after introducing him at a campaign rally at Pensacola Civic Center in Pensacola, Fla., Monday, Nov. 6, 2006. (AP Photo/Pablo Martinez Monsivais)
President Bush jokes with his brother Florida Gov. Jeb Bush on Monday, Nov. 6, 2006, in Pensacola, Fla., where Bush was drumming up support for local Republican candidates. (AP Photo/Mari Darr~Welch)
Former U.S. President George H. W. Bush, center, is joined by his sons, former U.S. President George W. Bush, left, and former Florida Gov. Jeb Bush, as he speaks to reporters after his parachute jump with the Army Golden Knights parachute team to celebrate his 85th birthday, Friday, June 12, 2009, in Kennebunkport, Maine. (AP Photo/Robert F. Bukaty)
President Bush greets his brother,former Florida Gov. Jeb Bush, right, and Jeb's son, George P. Bush, left, as he arrives at Palm Beach International Airport in West Palm Beach, Fla., Tuesday, March 18, 2008. (AP Photo/Gerald Herbert)
President George H. W. Bush, left, with his son former Florida Gov. Jeb Bush, right, enters the West Wing of the White House to meet with President Barack Obama Saturday, Jan. 30, 2010, in Washington. (AP Photo/Alex Brandon)
President George W. Bush, left, smiles while being introduced by his brother Florida Gov. Jeb Bush, right, at the Florida Victory 2004 rally on Sunday, Oct. 31, 2004 in Tampa, Fla. (AP Photo/Scott Audette)
This photo taken Feb. 15, 2011, show former Florida Gov. Jeb Bush greeting his mother, former first lady Barbara Bush, at the White House's 2010 Presidential Medal of Freedom ceremony in Washington, where her husband, former President George H.W. Bush is to receive the Medal. Jeb Bush has already heard his mother, Barbara, tell everyone âweâve had enough Bushesâ in the White House. In the lead-up to 2016 presidential campaign, the former Florida governor says heâs in his 60s and doesnât have to do everything his mom says. âI'm trying to avoid the family conversation,â he said. (AP Photo/Carolyn Kaster, File)
In this Oct. 22, 2002, file photo former first lady Barbara Bush makes a point as she campaigns for her son, Florida Gov. Jeb Bush, at Nova Southeastern University in Davie, Fla. Amid the celebration surrounding the opening of son George W. Bush's presidential library, Barbara Bush is brushing aside talk of her son Jeb running for president in 2016. When asked how she felt about it she told NBC's "Today" show, Thursday, April 25, 2013, "We've had enough Bushes." (AP Photo/Marta Lavandier, File)
Florida Gov. Jeb Bush, right, reaches out to grab his brother President George W. Bush before a speech Friday morning March 8, 2002 at America II Electronics in St. Petersburg, Fla. In the his remarks, Bush said he does not know whether Osama bin Laden is dead or alive but cautioned Americans against judging the success of the war on the fate of the terrorist mastermind. (AP Photo/Chris O'Meara)
Former first lady Barbara Bush laughs with her son, Florida Gov. Jeb Bush, during a campaign stop in Ellenton, Fla., Monday, Oct. 30, 2000. The two were campaigning for another of her sons, Republican presidential candidate Texas Gov. George W. Bush. (AP Photo/Chris O'Meara)
Republican presidential candidate Texas Gov. George W. Bush jokes with his brother, Florida Gov. Jeb Bush, left, during a bus ride to a rally at Florida International University in Miami, Fla., Sunday, Nov. 5, 2000. At left is New York Mayor Rudolph Giuliani. (AP Photo/Eric Draper)
Texas Republican Gov. George W. Bush, right, and Florida's Governor-elect, Jeb Bush, answer questions at a news conference in New Orleans Wednesday Nov. 18, 1998. A flood of media requests to interview the Texas governor and the Florida governor-elect prompted the sons of former President Bush to schedule a news conference. The governors are attending the Republican Governors Association. (AP Photo/Bill Haber)
Florida Gov.-elect Jeb Bush, left, laughs during a joint news conference in New Orleans Wednesday, Nov. 18, 1998, with his brother Texas Gov. George W. Bush. The Bush brothers are attending the Republican Governors Association meeting which runs through Friday. A flood of media requests to interview the Texas governor and the Florida governor-elect prompted the sons of former President Bush to schedule a joint news conference. (AP Photo/Bill Haber)
Former President George Bush, right, clenches his fist Sept.16, 1994 as he hugs son, Jeb during a Florida GOP fund-raiser in Tampa. After a hiatus, Bush has been hitting the campaign trail and lecture circuit with a vengence, raising millions for Republican candidates and getting digs in at President Bill Clinton along the way. (AP Photo/Chris O'Meara)
Former President George H. W. Bush, right, and son Jeb Bush chat with recruits at the Pinellas County jail's boot camp in St. Petersburg. FL., March 28, 1994. Jeb Bush, who is running for the Republican nomination for governor, was on a campaign swing with his father. (AP Photo/Peter Cosgrove)
Cheerleaders shout their encouragement as Florida Republican gubernatorial candidate Jeb Bush and former President George Bush applauds Barbara Bush, center, during her address to a rally on Oct. 10, 1994 at Church Street Station in Orlando, Florida. Jeb Bush is running for governor against incumbent Democrat Gov. Lawton Chiles. (AP Photo/Peter Cosgrove)
President George H. W. Bush talks with his son Jeb, during a round of golf at the Cape Arundel Golf Club in Kennebunkport ME., Aug. 27, 1990. The president is scheduled to meet with Canadian Prime Minister Brian Mulroney Monday, at his Walker's Point home. (AP Photo/Doug Mills)
MACDILL AIR FORCE BASE, UNITED STATES: US President George W. Bush (R) reaches out to shake hands with his brother Florida Governor Jeb Bush (L) shortly after Air Force One arrived at MacDill Air Force Base, Florida, 09 May 2006. AFP Photo/Paul J. Richards (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images)
Washington, UNITED STATES: US President George W. Bush (L) looks on as his brother Florida Governor Jeb Bush speaks 19 April, 2006. Governor Bush was among several governors who met with the president after an Easter trip to Iraq, Afghanistan and Kuwait. AFP PHOTO/Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
President George Bush (left) and brother Gov. Jeb Bush acknowledge cheering supporters at a fundraiser for the Republican Party of Florida at the Contemporary Resort at Disney World in Orlando, Florida, Friday, February 17, 2006. (Photo by Joe Burbank/Orlando Sentinel/MCT via Getty Images)
ST. PETERSBURG, FL - OCTOBER 19: U.S. President George W. Bush (L) and his brother Florida Governor Jeb Bush (R) smile while greeting supporters during a campaign rally at Progress Energy Park October 19, 2004 in St. Petersburg, Florida. Recent polls indicate Bush is maintaining a slight lead over his Democratic challenger U.S. Sen. John Kerry (D-MA). (Photo by Mark Wilson/Getty Images)
PARK CITY, UT - JANUARY 22: Jeb Bush is seen at Salt Lake City Airport on January 22, 2015 in Park City, Utah. (Photo by JOCE/Bauer-Griffin/GC Images)
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Bush, who associates say has been dining on grilled chicken and salad while snacking on nuts and also exercising, is hardly the first politician to aim for a leaner look ahead of an expected campaign.
Politicians entering a presidential campaign often decide to lose a few pounds to project a more vigorous image. Usually when they do so it means they are seriously considering a candidacy.
Former Arkansas Governor Mike Huckabee lost 110 pounds in the years before his 2008 bid for the Republican nomination. (He has gained some of it back). New Jersey Governor Chris Christie, who is also considering a run for the Republican nomination, underwent Lap-Band surgery two years ago and lost some of his considerable girth.
Bush's friends have noticed the weight loss and are envious.
"Like a lot of us, Jeb has struggled with his weight at times. I'm slightly irritated that I seem to have found every pound he's lost," said Bush friend Ana Navarro, a Miami-based Republican strategist.
"IT'S JUST A FAD"
Some nutritionists are opposed to Paleo since it involves eating a lot of meat, which could lead to a higher consumption of fat since many high-protein foods have higher fat levels than carbohydrates. Bush is not known to consult a nutritionist about the diet, and his team declined to answer questions about criticisms of it.
"It's just a fad, there's no magic to it," said Dr. Christopher Ochner, a weight loss and nutrition expert at The Mount Sinai Hospital in New York. "If you called it something else and just ate more lean protein and fresh fruits you would lose weight."
Ochner said there are "other more well balanced, less faddish diets out there."
But Loren Cordain, one of the people who popularized the diet, defended Paleo as a "lifetime program of eating."
"More power to him," Cordain said of Bush.
"Paleo is all about health and well being for all of us," said Cordain, who is professor emeritus at the Department of Health and Exercise Science at Colorado State University.
It is unclear how well Bush, 62, can stick to the diet given the various tempting delicacies that pop up on the campaign trail during long, stressful days.
There's the tantalizing fried Snickers candy bar that is a staple of the Iowa State Fair, Kringle pastries in Wisconsin, the jelly-filled "pazcki" doughnuts of Michigan. And there is pretty much a slice of pizza everywhere you go.
"When you go to a diner or a coffee shop, you'd be surprised how often patrons will offer you a doughnut, a piece of pie, something that is deep-fried, has sugar on it," said Kevin Madden, who was a frequent flyer as a senior adviser to 2012 Republican nominee Mitt Romney.
"At the Iowa State Fair, everything is deep-fried and on a stick. It's hard to resist," Madden said.
Bush has been known to stray on occasion from the diet. Sometimes in the evenings he'll have a glass of wine, which is not Paleo compliant.
Just last week at a "politics and pies" event in New Hampshire, suddenly he was holding a plate with a slice of blueberry pie on it.
"To hell with the diet," he said as he dove in. "Where are the french fries?"
But he's trying hard.
Faced with a heaping pile of scrambled eggs, hash browns and pancakes at a recent breakfast in Colorado, Bush snatched up the single slice of bacon on the plate and skipped the rest.
Nice try, said Cordain.
"He would be better off replacing the high-salt bacon with a grass-produced pork chop," Cordain said.
Those around Bush find themselves eating the Paleo way when they're with him because quite often that's all that is available.
Dr. Staffan Lindeberg of the University of Lund in Sweden has done several studies of the Paleo diet. He said people report that they were satisfied after eating fewer calories than on a standard diet.
But often, he said, Paleo dieters underestimate how many calories they've consumed so they might feel hungry again sooner than otherwise and need to eat again.
"I tell my patients they need to beware of that: If they start feeling hungry between meals and there are no healthy foods available, they might reach for the junk food," he said.