In 1858, when Walt Whitman sat down to write a manifesto on healthy living, he came up with advice that might not seem out of place in an infomercial today.

“Let the main part of the diet be meat, to the exclusion of all else,” Whitman wrote, sounding more than a little paleo.

As for the feet, he recommended that the comfortable shoes “now specially worn by base-ball players” — sneakers, if you will — be “introduced by general use,” and he offered warnings about the dangers of inactivity that could have been issued from a 19th-century standing desk.

“To you, clerk, literary man, sedentary person, man of fortune, idler, the same advice,” he declared. “Up!”

Whitman’s words, part of a nearly 47,000-word journalistic series called “Manly Health and Training,” were lost for more than 150 years, buried in an obscure newspaper that survived only in a handful of libraries. The series was uncovered last summer by a graduate student, who came across a fleeting reference to it in a digitized newspaper database and then tracked down the full text on microfilm.

Now, Whitman’s self-help-guide-meets-democratic-manifesto is being published online in its entirety by a scholarly journal, in what some experts are calling the biggest new Whitman discovery in decades.

“This is really a complete new work by Whitman,” said David S. Reynolds, the author of “Walt Whitman’s America” and a professor of English at the Graduate Center of the City University of New York, who was not involved with the find.

The series, with its disquisitions on bodily humors and “the great American evil — indigestion,” shows Whitman’s long-known immersion in the health science, or pseudoscience, of his era. Wackier aspects aside, scholars say, the series also sheds fresh light on the poet in the crucial period of the late 1850s, when he was preparing the landmark 1860 third edition of “Leaves of Grass” and probably working on the poems of homoerotic love that are central to the Whitman we know today.

“These are the most interesting and mysterious years in Whitman’s biography, and now we have this major journalistic series right in the middle of it,” said Ed Folsom, the editor of The Walt Whitman Quarterly Review, the online journal that is publishing the series in its spring issue.

“One of Whitman’s core beliefs was that the body was the basis of democracy,” Folsom, a professor of English at the University of Iowa, continued. “The series is a hymn to the male body, as well as a guide to taking care of what he saw as the most vital unit of democratic living.”

The series was discovered last summer by Zachary Turpin, a graduate student in English at the University of Houston who was browsing in digitized databases of 19th-century newspapers, entering various pseudonyms that Whitman, a prolific journalist, was known to have used.

“It’s kind of a sickness I have in off hours,” Turpin said.

During one search, up popped a brief reference in The New-York Daily Tribune on Sept. 11, 1858, to a series on manly health by “Mose Velsor,” one of Whitman’s favorite pen names, which was about to appear in another paper, The New York Atlas. (While his notebooks have long been known to contain a handwritten draft of an advertisement for a series on “manly health,” scholars have never known whether Whitman — much of whose voluminous journalism has been lost — had ever actually written such a series.)

When Turpin ordered microfilm of the relevant issues of The Atlas, which survive in only a few libraries and have not been digitized, he was stunned to find 13 installments.

“It took about 24 hours for it to sink in,” he said.

“Manly Health and Training” was published in weekly installments starting in September 1858, a time when Whitman, then 39, was licking his wounds over the flop of the first two editions of “Leaves of Grass” and churning out hundreds of words a day as a journalist.

He had also begun an intense relationship with Fred Vaughan, an Irish stage driver, and most likely begun work on the series of poems known as “Calamus” (later included in the 1860 “Leaves of Grass”), whose evocations of homoerotic love are echoed in “Manly Health,” Folsom said.

“Manly Health,” with its references to “inspiration and respiration” and the importance of “electricity through the frame,” also echoes the language of earlier poems like “Song of Myself” and “I Sing the Body Electric,” recasting their themes in the more concrete spirit of a self-improvement manual.

“There’s a kind of health-nut thing about ‘Leaves of Grass’ already,” Reynolds said. “This series sort of codifies it and expands on it, giving us a real regimen.”

Whitman’s first installment strikes a vatic, exclamatory note: “Manly health! Is there not a kind of charm — a fascinating magic in the words?” he writes, before outlining the path to “a perfect body, a perfect blood.”

That torrent of advice that follows touches on sex, war, climate, bathing, gymnastics, baseball, footwear, depression, alcohol, shaving and the perils of “too much brain action and fretting,” in sometimes rambling prose that draws freely, Turpin notes in an introductory essay, from Whitman’s reading in publications like Water-Cure Journal and The American Phrenological Journal.

“It’s sort of an insane document,” Turpin said.

While the exhortations are mainly sunny, some installments have disturbing undertones, Turpin noted. In one, Whitman — who would go on to abhor the bloodshed of the Civil War — extols the virtues of bare-knuckle boxing (then illegal), on the grounds that it will help America become “a hardy, robust and combative nation” imbued with “the love of fight.”

Whitman emphasizes that men of all physiques can benefit from training, but he includes a racially tinged discussion of the advantages of “our Teutonic ancestors” and other people of the northern climes.

“While Whitman doesn’t state openly that a great America is a white America, he does suggest these other races will fall away,” Turpin said.

Reynolds said he agreed that the text shows hints of Whitman’s later turn toward ethnographic pseudoscience (a kind of “pre-eugenics,” Reynolds said), a topic that has received substantial attention from scholars in recent years.

But the most striking thing, Reynolds said, is its emphasis on moderation, and a holistic vision of the relationship between mental and physical health, in contrast to the radical temperance advocates, water-cure partisans and dietary reformers who sprung up across mid-19th-century America.

Whitman, who lived to a ripe 72, is really advocating “getting up early, having a walk, getting the benefit of fresh air and lots moderate exercise,” Reynolds said. “One could do worse than follow his advice.”

© 2016 The New York Times Company