Star. Yet another skewed food:  even the simplest sandwich can contain any number of mysterious food additives.

What's Lurking in Your Pantry

As a serious cyclist, I can report that there are no subjects that come up as often on rides as nutrition and weight loss. No matter how svelte a rider already is, losing "10 more pounds" is the mantra, and we're all true to our word until it comes to actually eating food, at which point we encounter two general obstacles to healthy eating. First, there is our evolved propensity to enjoy sweet and fatty foods, because in the Paleolithic environment of our ancestors such foods were both rare and nutritious and we have no natural satiation mechanism that signals our brains to stop consuming them. Second, there is modern nutritional science, which knows how to trick our brains into wanting to consume foods that are designed to be tasty and have long shelf lives.

The processed-food industry accounts for about 70% of the calories that Americans consume annually, including (per person): 33 pounds of cheese, 70 pounds of sugar and 8,500 milligrams of salt (double the recommended dose), almost none of which comes out of your salt shaker. As a result, about a third of adult Americans and a fifth of children are clinically obese.

In "Pandora's Lunchbox," journalist Melanie Warner describes how she began her investigation into the processed-food industry as a new mother whose young sons wanted to consume mass quantities of sweet snacks like Oreos and Pop-Tarts. Even when you try to eat healthy meals, she notes, you will find yourself consuming unpronounceable ingredients.

Consider the popular Subway sandwich, an icon of wholesome weight loss ever since Jared Fogle shed copious pounds on what became known as the "Subway diet." Ms. Warner reveals the 105 ingredients of Subway's Sweet Onion Chicken Teriyaki Sandwich. The chicken alone contains such chemicals as potassium chloride (salt), maltodextrin (a starchy thickener), autolyzed yeast extract (a cheap substitute for MSG), gum arabic (tree sap used as a stabilizer), soy protein concentrate (cheap protein additive), and sodium phosphates (more salt!). The Italian white bread, meanwhile, comes equipped with ammonium sulfate (inorganic salt often used in fertilizer), azodicarbonamide (a flour bleaching agent), potassium iodate (a maturing agent for increasing the speed of baking dough), sodium stearoyl lactylate (a fat and sugar replacement for dough conditioning) and natural flavor (natural!). Some of these ingredients provide flavor (autolyzed yeast extract); some extend shelf life (ammonium sulfate); others are simply cheaper than alternatives (soy protein concentrate).

If you were to make this sandwich at home, Ms. Warner admits, you might be able to avoid these substances, but then again, where did you get the chicken and the bread? Supermarkets and the distributors they purchase from face the same challenges as Subway: You can have your bread without all the chemicals, but the loaf will cost two to three times more and go bad in a day or two. There's a reason you spend more at Whole Foods.

Of course, you could also bake your own bread, using fresh ingredients from your wheat field, then go over to your backyard chicken coop and slaughter one for your meal. But despite the efforts of today's "locavores" (who eat only locally produced foods), the pre-modern world of Babe the pig frolicking about the family farm is long gone. For the most part, that's a good thing. In 1800, the vast majority of people were farmers feeding a total U.S. population of 5.3 million. Ms. Warner recounts what life was like in poor areas before the introduction of vitamins into food substances, the fortification of white flour and milk, and the widespread availability of items like orange juice: Many people suffered from rickets (because of insufficient vitamin D and calcium), scurvy (vitamin C), pellagra (vitamin B3) and beriberi (vitamin B1).

The 2013 Super Bowl commercial for Dodge Ram Trucks featured Paul Harvey's moving narrative "And God Made a Farmer." It could have been followed by, "And after the people went forth and multiplied, God Made a Food Chemist."

Ms. Warner's gripping exposé is tempered with a sense of the trade-offs entailed. Michael Moss, by contrast, describes the food chemists' craft in language that makes them sound cabalistic: In "Salt Sugar Fat," the New York Times reporter criticizes corporate scientists for being "deliberate and calculating" when they employ "the high math of regression analysis and intricate charts to plot what industry insiders call the 'bliss point,' or the precise amount of sugar or fat or salt that will send consumers over the moon.

Even when these corporations seek to improve the "nutritional profile" of a product, Mr. Moss finds fault, describing "one of the industry's most devious moves: lowering one bad-boy ingredient like fat while quietly adding more sugar to keep people hooked." Hooked? Like a drug? Yes. "Some of the largest companies are now using brain scans to study how we react neurologically to certain foods, especially to sugar. They've discovered that the brain lights up for sugar the same way it does for cocaine." Cocaine? This is hyperbole.

I was grateful for—if disturbed by—Mr. Moss's revelations when it comes to the basic facts of what's in the foods we consume. (I just checked the back of the package of my honey-smoked turkey breast and was nauseated to learn that turkey is only one of 13 ingredients.) But sometimes his portrayals seem to ignore the incentives that drive the food business. What are food chemists—who are employed by large food corporations and tasked with producing food products desired by food consumers—supposed to do? We already regulate the food industry for consumer safety and protection. The best defense, as in any other industry in which we allow markets relative freedom to prosper, may be caveat emptor.

To that end, Mr. Moss's book will prove vital reading for the discerning food consumer. Mr. Moss realizes this, too, suggesting that readers treat his book as "a wake-up call to the issues and tactics at play in the food industry." With more unnecessary hyperbole, though, he wants us to "think of the grocery store as a battlefield, dotted with landmines itching to go off." Armed with knowledge of "the formulas, the psychology, and the marketing" that these food engineers employ to persuade us, "we, ultimately, have the power to make choices. After all, we decide what to buy. We decide how much to eat." This helpfully puts the onus back on consumers, who, after all, are free to choose.

Melanie Warner, for her part, admits that no one can avoid all processed and packaged foods. In the spirit of "everything in moderation," she suggests reversing the ratio of the American diet today, so that our processed-food intake goes down to 70% and the rest comes from "foods that have had a relatively direct and boring journey from the farm—foods that are, for the most part, grown not made." It's advice reminiscent of Michael Pollan's maxim, which I've found to be the simplest and most straightforward: "Eat food. Not too much. Mostly plants."

If only I could hold myself to that.