Ultra-Processed People references numerous studies that aim to prove the value of experiments and their centrality in understanding diet and health. A case in point is the 2017 experiment conducted by Kevin Hall with 20 volunteers comparing the impact of UPF and non-UPF diets. As van Tulleken highlights, this “provided tantalizing evidence that Monteiro’s theory may indeed explain the rise in obesity across populations” (58). The study, showing a rise in weight among volunteers on a UPF diet over a two-week period, gave legitimacy to the NOVA scale and prompted further research into its impacts. Indeed, Hall’s study was one of the things that led van Tulleken to look more closely at the phenomenon of UPF. Likewise, a similar study by Hall in 2012 helped show that sugar does not cause weight gain. Comparing two groups on high- and low-carbohydrate diets, with equal caloric intake, the study found that “there was no difference between the groups in terms of the effect of fat or sugar on metabolism” (113).

This disproved the hypothesis that insulin from sugar intake is the main culprit for rising obesity levels, as well as the thesis that lack of exercise is responsible.