With the notable exception of the current prevalence of obesity in Western societies, there is little reason to believe that fattening up the constitutionally lean is any easier than inducing leanness in the obese. For successful fattening, the excess calories consumed have to be stored as fat, rather than expended in metabolism or physical activity or stored as muscle. This isn’t a given, considering these alternative uses for the calories. Continuing to consume excess calories is necessary, too—the person being fattened has to continue eating long after becoming sated—and these calories also have to be stored as fat.

In the early 1970s, the British physician John Garrow attempted to add twelve hundred calories a day to his daily diet, hoping to sustain it for a hundred days. After failing with several methods, he found that he could accomplish his goal by keeping chocolate biscuits on hand and, “whenever the prospect didn’t seem too revolting, eating however many of these biscuits that I could.” He managed to gain fifteen pounds in sixty days and then gave up the experiment and lost the weight in fifty days. “I learned that for me it is difficult to move my weight at all rapidly in any direction,” he said, “and I saw absolutely no reason to suppose that obese people would find it easier than I did.”

Various foods have been used to induce extensive fattening. The tribes that Speke visited relied on milk to fatten their women. In the mid-1970s, the French ethnologist Igor de Garine documented two male fattening sessions of the Massa tribe of northern Cameroon. In an individual ritual, the man ingests both milk and a porridge made from sorghum, a cornlike grain that provides, like sugarcane, a sweet syrup from the stalk. In 1976, Garine reported, one Massa tribesman gained seventy-five pounds on this ceremonial binge, apparently averaging ten thousand calories a day throughout. In a group fattening ritual, the men consume thirty-five hundred calories a day, rather than their usual twenty-five hundred, the excess consiting of milk and porridge. The weight gain tends to be fifteen to twenty pounds. The Massa are cattle herders, and their staple diet is primarily milk. This fattening, therefore, is accomplished by the addition of carbohydrates almost exclusively—one thousand to seventy-five hundred calories a day of sorghum.