Roxane Gay set out wanting to write about fat, but she “started to think, ‘Well, what would it be like to write a memoir of my body?’ ” (Jay Grabiec)

Roxane Gay begins her new book — the hardest she’s ever had to write — by describing what it isn’t.

“The story of my body is not a story of triumph,” Gay writes in the opening pages. “Mine is not a success story.”

Instead, it’s a searing account of the essayist’s lifelong struggle with her weight, which once topped 500 pounds. “Hunger: A Memoir of (My) Body” is no weight-loss memoir, she is quick to explain. There’s no tidy resolution here, no willowy woman on the book jacket holding the waistband of her old pants an arm’s reach from her new body.

“I wished I could write that book,” says Gay, 42, a once-obscure­ academic and fiction writer whose tart takes on social issues and pop-culture built a loyal online audience and helped launch a best-selling 2014 collection of essays, “Bad Feminist.”

“I’d wanted to write about fat for a while, and I didn’t quite know how,” she says. “And then I started to think, ‘Well, what would it be like to write a memoir of my body?’”

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The resulting book turned into a portrait of resilience in the aftermath of trauma: When Gay was 12, a boy she adored lured her to a cabin in the woods near her Nebraska home, and he and a group of his friends raped her.

“They did things I’ve never been able to talk about, and will never be able to talk about,” she writes. “Those boys treated me like nothing so I became nothing.”

For years, she told no one. Food became a vital source of comfort; her doting parents, both Haitian immigrants, were alarmed as their quiet daughter gained more and more weight. “They knew nothing of my determination to keep making my body into what I needed it to be — a safe harbor rather than a small, weak vessel that betrayed me,” Gay writes.

Gay has long focused her work on matters such as sexuality, gender, race, body image, violence. Her most recent collection of short stories, “Difficult Women,” is filled with quirky, surrealist tales of sisterhood, loss and toxic relationships. But of all her work so far, “Hunger” is certainly the most vulnerable. Which made it the most painful story to tell, Gay says.

Writing is usually a source of joy for her; she assumed the words would flow easily. But the prospect of revealing herself so completely proved terrifying. She procrastinated, and the book, originally scheduled for publication last year, was delayed. In April 2016, Gay explained to her 200,000 Twitter followers: “There is no mystery beyond I still haven’t turned it in because the book is scary.”

It was a surprising confession from a writer who has never shied from personal disclosure or controversy. Starting as a creative writing professor at Eastern Illinois University, she made her name with trenchant essays for online outlets such as Salon and the Rumpus. She wrote about the dark pull the saccharine “Sweet Valley High” books had over her childhood; she examined the troublesome ways that rape is represented in news coverage; she condemned the fixation on Trayvon Martin’s hoodie as a way to shift the blame for his murder.

Roxane Gay, center, on a panel at the New Yorker festival in 2015, with Jill Lepore and Geraldo Cadava. (Thos Robinson/Getty Images for the New Yorker)

Gay, now on faculty at Purdue University, is the kind of writer who is usually game to jump into a Twitter battle or slap down a troll. In January, she pulled a forthcoming book from Simon & Schuster in protest, after the publishing house signed far-right provocateur Milo Yiannopoulos.

But this was different. This was her own body.

“When you’re fat, your body is not a secret, but you still hold on to secrets; you pretend, of course, that people don’t see you the way you know they see you,” Gay says. “And so to expose myself and this history of my body . . . it’s not something I took any pleasure in.”

Over “Hunger’s” 88 short chapters, she explores the loneliness and pain of her body’s constraints. There is the exhaustion of constant scrutiny, of unavoidable logistical challenges. (How sturdy is a chair? How high the step onto a stage?) She conveys the relentless anxieties that fuel a “constant, destructive refrain”: I am the fattest person in this shopping mall. I am the fattest person on this panel. I am the fattest person in this casino. I am the fattest person.

But she also chronicles her perseverance, her formative relationships, and her ongoing quest for healing and peace. Although she turns a critical eye inward, she has much to say about a culture that glorifies TV shows such as “The Biggest Loser” and “My 600-lb Life” but makes little effort to accommodate larger people or support their physical and mental health.

“I really just wanted to talk about what obesity — no, I hate that word — what fat looks like, beyond what people generally see, where you’re talking about someone who is 60 or 100 pounds overweight,” Gay says. “I wanted to wrest control of that narrative back from the people who have seized it.”

The book offers a pointed retort to the smug strangers who shoot Gay sidelong glances at the gym or gawk as she settles into an airplane seat: Here is everything you could have possibly wanted to know about why and how someone comes to live in this body.

“We are human, these are our bodies, and it’s nobody’s business. You don’t get to judge,” Gay says. She hopes the book “increases the empathy that people have for others in different kinds of bodies. And maybe it will make people mind their business a little bit more.”

As for what it means for her — she’s still living her way into that answer.

“Writing the book has allowed me to just take a hard and necessary look at myself that I had been unwilling to take — at how I got from then to now,” she says. “And to just be honest with myself.”

And has that brought her closer to the peace she seeks?

“We’ll see,” she says. “It’s too soon to know.”

Roxane Gay will speak about “Hunger” on June 20 at 6:30 p.m. at All Souls Unitarian Church in Washington. The event is free, but space is limited.