Diet and fitness books have always depended on science to validate their claims. “Studies show,” “researchers found,” “participants exhibited,” “scientists have observed”: any reader of the genre is familiar with these pronouncements. Often, the hard science behind health, along with the lab-coat jargon used to describe it, has been relegated to something like the role of chaperone: necessary to lend authority to a book, but hidden in the background.

Many of the latest diet and fitness books, however, suggest that readers’ appetite for science—hard data, heady terminology, and cutting-edge theories—is growing. From genetics and hormones to gut health and inflammation—to say nothing of the ongoing feud between paleo diehards and “nutritarians”—this season’s offerings may be the genre’s geekiest yet.

Justin Schwartz, an executive editor at Houghton Mifflin Harcourt who worked on registered dietician Molly Morgan’s forthcoming Drink Your Way to Gut Health (Mar. 2015), attributes the surge of interest in science (particularly in probiotics, gut health, and gluten-free diets) to what might be called the WebMD phenomenon. “People don’t go the doctor and say, ‘I’m sick, what’s wrong with me?’ ” he explains. “They say, ‘I’ve already spent three hours researching it. I know the medication that I probably need.’ ” Readers can appreciate science, he says, “because they’re willing do the homework themselves.”

At Viking, The Gene Therapy Plan, by physician Mitchell L. Gaynor (Apr. 2015), explores how dietary and lifestyle changes influence the way genes express themselves. Carole Desanti, v-p and editor at large at Viking, says the interest in genetic science is driven by readers’ desire to take control of their health. The idea that genes don’t entirely determine one’s destiny is, she says, “an empowering message at a time when often ‘science’ and ‘genetic’ are used to reinforce more fatalistic ideas.”

As health books have become more science oriented, they’ve also become more diverse in their approaches. Biggest Loser trainer Bob Harper’s forthcoming Skinny Habits: The Six Secret Behaviors of Thin People (Ballantine, Apr. 2015), draws on everything from behavioral economics and cognitive behavioral psychology to sleep hygiene. Marnie Cochran, an executive editor at Ballantine Bantam Dell, says she’s seeing a demand for “more sophisticated science,” adding that the book will include images of functional MRI (fMRI) scans and information about the neurology of habit formation. Habits follows Harper’s The Skinny Rules (2012), which, according to outlets reporting to Nielsen BookScan, has sold some 152,000 copies in hardcover.

Dave Asprey’s The Bulletproof Diet (Rodale, Dec.) adopts a technical approach to wellness, incorporating findings about the brain and nervous system into a program that the author refers to as bio-hacking. Mary Ann Naples, senior v-p and publisher at Rodale, says Asprey’s perspective on health is shaped by his experiences as a Silicon Valley computer hacker: “He knows the techniques of analyzing a system.” She hopes that his reputation in the tech community will attract readers who don’t normally buy diet and fitness books, men as well as women.

The Bulletproof Diet advises eating saturated fats—the recipe for bulletproof coffee, for example, calls for adding MCT oil and butter—in contrast to long-standing nutritional wisdom. In this regard, Asprey’s in step with recent studies that show the benefits of fat (or at least debunk the idea that it’s inherently unhealthy).

Another book that counters popular notions about diet is Proteinaholic: How Our Obsession with Meat Is Killing Us and What We Can Do About It, by Garth Stein (HarperOne, Apr. 2015), which argues that animal protein, the sacred cow of many popular diets (most notably paleo), contributes to obesity, diabetes, and heart disease. Gideon Weil, v-p and executive editor at HarperOne, says the book draws on Stein’s work as a surgeon in Texas, where obesity rates run high.

Still, the paleo craze shows little sign of letting up. Loren Cordain, who began to popularize the so-called caveman diet in 2001 with the publication of The Paleo Diet (Wiley), will be publishing The Real Paleo Diet Cookbook (HMH) in March. Anne Ficklen, an executive editor at HMH who worked on the book, says it is intended in part as a corrective to the paleo explosion that has taken place over the last few years. “The science is the driving principle” behind the cookbook, Ficklen says.

Publishers are so confident in science’s appeal that several put the word right on the cover: The Science of Skinny Cookbook, by Dee McCaffrey (Da Capo, Jan. 2015); The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss, by Kristen Mancinelli (Ulysses, Jan. 2015); Smart People Don’t Diet: How the Latest Science Can Help You Lose Weight Permanently, by Charlotte N. Markey (Da Capo, Jan. 2015); Body Of Truth: How Science, History, and Culture Drive Our Obsession with Weight—and What We Can Do About It, by Harriet Brown (Da Capo, Mar. 2015); and Secrets from the Eating Lab: The Science of Weight Loss, the Myth of Willpower, and Why You Should Never Diet Again, by Traci Mann (HarperWave, Apr. 2015).

Facts and Figures

Hard science may be newly assertive in the diet and fitness genre, but a ton of titles this season stick to the classic trick of putting numbers on the cover.

It’s long been common wisdom that numerical promises—lose 10 pounds in 10 days!—are catnip to readers, whether on magazine covers or book jackets. But is there a number that readers find especially appealing? Or one, like 666, that drives them away?

Edward Ash-Milby, a buyer at Barnes & Noble who focuses on health, fitness, and cooking titles, says he doesn’t give much thought to which numbers work and which don’t. The important thing, he said, is to include them. “I do like to see some type of promise being described on the jacket,” he said. Not too surprisingly, he says that for quantities of time, small numbers are best, while “reasonably large-ish” figures are ideal when talking about potential weight loss.

Cochran at Ballantine Bantam Dell says the figure on a book jacket typically originates with the author, not the publisher. She adds that books tend to be divided into two groups: those with flashy numbers promising quick results and those with more grounded figures promising deeper change. “A lot of people buy books that say ‘lose a pound a day for seven days’ because they’re going to a reunion,” Cochran says. “But no one expects realistically that the weight’s going to stay off. That said, we make our best effort to meet both those needs.”

Sarah Pelz, an executive editor at Grand Central who edited Rocco DiSpirito’s Cook Your Butt Off! Lose up to a Pound a Day with Fat-Burning Foods and Gluten-Free Recipes (Feb. 2015), explains that some numbers are factored into a book’s concept from the beginning, while others are developed later on. But all must pass a reality check. “We never put a number on the cover that hasn’t been vetted by the author,” she says.

HMH’s Justin Schwartz, who worked with Dallas and Melissa Hartwig on their 30-day bad-habit-breaking guide, The Whole30 (Apr. 2015), says he shies away from “really aggressive books that say they’re going to change your life in hours. It’s almost not ethical. It’s promising too much.”

Daniel Lefferts is a freelance writer living in New York City.

Below, more on the subject of diet and fitness.

The Pleasure Principle: Diet & Fitness 2014

Losing Weight, Gaining Readers: Diet & Fitness 2014

More of the Season’s Diet & Fitness Titles: Winter 2014–Spring 2015