Of course, if you commit to drinking the premeasured Soylent servings for all your meals, you don’t need to worry about overcompensating elsewhere. As long as you can ignore any cravings or stomach rumbles and stick to stirring up your powder, you’ll be guaranteed 1,800 calories a day with the women’s formula or 2,400 for the men’s. (These numbers are on the “sedentary” end of the USDA’s recommendations, so you may find them lacking if you exercise. Be glad Rhinehart abandoned his original “caloric restriction” recipe with only 1,550 calories a day.) Rhinehart plans to offer other options in the future. “As time goes on it will become more and more customizable and personalized,” he wrote in an email.
For now, Soylent treats the government’s dietary recommendations like a set of strict operating instructions. But they’re intended only to be an approximation of what keeps us healthy in a diet of actual food. “A basic premise of the Dietary Guidelines is that nutrient needs should be met primarily through consuming foods,” the USDA writes in its Dietary Guidelines for Americans 2010.
“Calorie and nutrient requirements may differ from person to person and can depend on factors such as age, gender, height, weight, physical activity level, medical conditions, etc.,” says Kim Croteau, a dietician with the USDA’s Food and Nutrition Information Center. Smokers, vegetarians, and anyone who is ill also have nonstandard needs, according to Dietary Reference Intakes, a book put out by the Institute of Medicine (on whose research the USDA bases its recommendations).
In fact, the Institute of Medicine says, “It is nearly impossible to determine what an individual’s exact requirement for a nutrient is.” Even when it comes to those numbers on the side of your cereal box, “It is important to keep in mind that ... there is considerable uncertainty about these values.”
Rhinehart insists on his blog that Soylent has made him healthier in astonishing ways: “My physique has noticeably improved, my skin is clearer, my teeth whiter, my hair thicker and my dandruff gone.” He says the extra energy from Soylent lets him run miles and miles at the gym that he never could before—though he doesn’t address the possibility that he’s got it backward, that the added exercise accounts for his better health and energy (not to mention “physique”).
“My mental performance is also higher,” Rhinehart claims, adding that he can now navigate better without using GPS (he has not moved to a new city) and that he enjoys music more. Rhinehart is hardly an objective observer of his own behavior as a research subject. Expectations matter, even when it comes to cherry gelatin cubes. So does the more than $635,000 that Soylent’s crowdfunding campaign has raised as of June 17—more than six times the original goal. The campaign ends later this week.
When those thousands of backers get their first shipments of Soylent, they might provide new data about how well the substance meets people’s nutritional needs. But we will probably never find out how effective the food of the future is because people may not be able to stick with it.
“One of the best diets ever is the eat-all-you-want-of-one-food diet,” Mattes says. “It will work! For a short time. But due to the lack of sensory stimulation, the monotony of the single food, nobody can really follow it.” Soylent’s predecessors, the classic meal-replacement drinks like Slim-Fast, may help some people regulate their calorie intake—but they aren’t meant to be eaten full-time.
I asked Mattes whether people following any all-liquid regimen can expect to always feel a little hungry and unsatisfied. There’s not enough data to answer the question for sure, but as he said: “That would be my expectation.”
Even Rhinehart has left behind the strict Soylent diet that kicked off his experiment. “I still enjoy food,” he told me. “I just don’t crave it more often than the weekends.” My friend, despite the travel mug, doesn’t plan on drinking Soylent for more than three meals in a row.
Soylent backers may enjoy their beige shakes for a while, but they won’t become the fantasy diesel-engine bodies of the future. They’ll still be messy, expectation-ridden, variety-craving human machines.