Mayer worked with the dietician and chief medical officer of the company that owned the Bengali mill and an accompanying bazaar, and it was these Indian colleagues who assessed the physical activity and diet of the resident workers. These men, as Mayer reported, ranged from “extraordinarily inert” stall holders “who sat at their shop all day long,” to those engaged in intense physical activity who “shoveled ashes and coal in tending furnaces all day long.”

The evidence reported in Mayer’s paper could have been used to demonstrate any point. The more active workers in the mill, for example, both weighed more and ate more. As for the sedentary workers, the more sedentary they were, the more they ate and the less they weighed. The twenty-two clerks who lived on the premises and sat all day long weighed ten to fifteen pounds less and were reported to have eaten four hundred calories more on average than the twenty-three clerks who had to walk three to six miles to work, or even than those five clerks who walked to work and played soccer every day.

Nonetheless, Mayer claimed that the study confirmed the findings of his rat experiment. He based his conclusion exclusively on the relative girth of thirteen stallholders and eight supervisors. These men weighed, respectively, fifty to sixty pounds and thirty to forty pounds more than the clerks who worked for them, and yet, according to Mayer’s data, consumed the same amount of calories. Mayer implied that they added this extra weight because they were somehow even less active than those employees whose jobs entailed sitting all day, but he had no evidence for it. It’s also possible that their relative wealth introduced other dietary factors that could have explained the dramatic differences in weight. Either way, as John Garrow noted, these findings would never be replicated, which is why such authorities as the Institute of Medicine of the National Academies of Science still cite Mayer’s study today as the only evidence for the proposition that “too little” exercise can disrupt the mechanisms that normally regulate food intake.

Mayer’s advocacy of exercise for weight control did not go unchallenged. After his 1965 New York Times Magazine article, entitled “The Best Diet Is Exercise,” physicians working with obese patients wrote to the newspaper saying that Mayer’s faith in exercise was unreasonable and flouted common sense. “As much as Dr. Mayer minimizes the thirst and appetite increases after exercise, my patients all seem to be thirstier after tennis and find it difficult to stick to plain water,” wrote Morton Glenn of New York University College of Medicine; “and who hasn’t heard someone say: ‘This walk all the way home sure gave me an appetite!’ Exercise can and does increase thirst and appetite, in most persons, in most situations, and most people respond to these sensations accordingly!”