She is a champion of women: Her second book, Knowing Your Value, took on the inequities women put up with in pay and in the workplace, and many of her off-air commitments revolve around empowering women and championing their role in our economy. She has an unbelievable capacity for work: Viewers might think a morning show anchor’s day is done by early afternoon, but Mika and Joe go on road shows, produce specials, give speeches, write columns, write books, and more.

And that brings me to Mika’s new book, Obsessed: America’s Food Addiction — and My Own, which, if you’re a viewer of the show, you probably know all about thanks in part to Joe’s frequent discussion and praise of it since it came out last month. If you’re a viewer you also probably know Mika’s outspoken views about the problems with obesity in our country and the food industry’s role in helping create those problems. What wasn’t known until the release of Obsessed was the deeply personal place this passion comes from: Mika’s own lifelong struggle with food.

Mika “goes there” in her books. She went there in All Things at Once when she talked about falling down the stairs with her newborn in her arms after working around the clock, exhausted. She went there in Knowing Your Value when she wrote about nearly quitting Morning Joe in 2008 because she made 14 times less than Joe (who was as perplexed as she was and fought for her). Her candor and honesty in her writing — they have become her trademark — make her sympathetic and real.

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But nowhere has Mika “gone there” like she has in Obsessed, in which she reveals for the first time her lifetime battle with binge eating — a obsession she refers to not as a disorder but an addiction, and that’s what it reads like. The writing is vivid and raw: In high school, she would “scarf down” Big Macs and “scrape clean” family-size cartons of ice cream. In college, she would eat a large Domino’s pie alone in her dorm room then go for a 10-mile run to repent.

This obsession has followed Mika throughout her life, and she relays breakdowns she has suffered even more recently while on the road with Morning Joe. There is a powerful episode involving a Mexican take-out order and the back of a Suburban as the group is on the way to the airport after a long day in Texas; there is a hauntingly recounted middle-of-the-night encounter with Nutella.

The binges are obsessively counterbalanced with epic amounts of exercise and a hyper-restrictive diet of at times 1,200 calories a day. One of the most interesting scenes in the book is the diagnosis Mika receives from an eating disorder specialist of orthorexia nervosa, a little-known disorder characterized by an obsession with eating healthy food (you probably recognize this in someone you know). This is the root of much of the problem, it turns out. Eating fats, as the nutritionist tells her, is important because fat provides a feeling of satiety; filling yourself with kale and flax seed and water won’t ever allow you to feel full; binging fills that hole.

The book isn’t just about Mika; it kicks off with a frank conversation she had with her close friend Diane Smith, also a successful television journalist, in which Mika called Diane out on her escalating weight — and came clean with her own issues after Diane accused her of being thin and perfect. After tearful confessions, the two make a pact — Diane will lose 75 pounds, and Mika will gain 10 pounds and break her obsession. This challenge, and Diane’s own struggle with weight, which is one more readers may relate to, frames the book.

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Peppered throughout this narrative are vignettes and first-hand accounts of similar struggles with food and eating from many of the same buzzy names that appear on the set of Morning Joe. Missouri Senator Claire McCaskill, New Jersey governor Chris Christie, NBC chief medical editor Dr. Nancy Snyderman relay sometimes harrowing stories of their battles with weight. (On a lighter and bittersweet note, the late, great Nora Ephron is here, too, talking about the eating strategy in her household: Calories were dedicated only to food that tastes good, and anything else was designated NWE — “not worth eating.”)

Mika spends a good deal of the book discussing the need to overhaul the food system and the need for the large food companies to do their part. She raises a powerful question about what’s in our food when she asks why don’t people sit down and scarf down a supersized bowl of broccoli, and spends a lot of time talking about the science behind our response to and cravings for certain food. She also includes fresh points in the obesity discussion, like the link between childhood obesity and bullying and the fact that obesity is shrinking the pool of potential military recruits; according to military leaders, she writes, one in four young people is “too fat to fight.” (More recently, shocking mortality research on immigrants has shown that the longer immigrants live in this country, the higher their rates of heart disease, high blood pressure, and diabetes — going against the very notion that coming to America will give them a better life.)

For all these points, though, to me the most important aspect of the book is the light shed on issues around food and eating that so many people face every day and don’t talk about. We have made it a specialty at Fortune to cover powerful women in business, and I’ve noticed that this topic has come up more lately. I know, thanks to off-the-record conversations and don’t-tell-anyone-but-do-you-know-that-she-suffers-from-it-too, that this is an issue that afflicts many powerful people, men and women alike — but especially women, and even powerful, successful women. Eating issues are in many ways the very last taboo; people would sooner talk about sex or money than their powerlessnesss over food.

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But not Mika, who not only comes clean but freely admits she is not out of the woods yet: the Nutella episode, for instance, happened in 2012. “The truth is that I live under a daily tyranny of food cravings,” she writes. She is well aware that her story may be hard for many people to sympathize with — a thin, beautiful, successful woman has problems and likes to eat Nutella with a spoon? Oh, woe is me. But Mika says bring on the attacks, if that means it gets the conversation going.

Get the conversation going Obsessed does. And for that reason alone, it is an incredibly brave and important piece of writing. In the end, Mika gained close to 10 pounds (and Diane has lost 75 and counting), and while still aware that every day is a challenge, she is healthier and happier. Let’s hope she continues to be — and that others will come forward and deal with this issue as courageously as she has.