1FAS Center for Systems Biology, Harvard University, 2Department of Human Evolutionary Biology, Harvard University, 3Department of Biological Sciences, University of Alabama
Friday 10:15-10:30, Ballroom B
Research into the energetic consequences of food processing has focused largely on its role in increasing the proportion of food nutrients absorbed within the gastrointestinal tract. However, by disrupting the structural integrity of food, processing by thermal and non-thermal methods can also be expected to reduce diet-induced thermogenesis (DIT), the cumulative energy expended on food ingestion, digestion, absorption and assimilation. DIT responses to unprocessed versus processed diets have not previously been assessed in humans or relevant animal models. Here we use open-flow respirometry to quantify DIT in adult rats fed standardized meals of lean meat or starch-rich tubers that were unprocessed, pounded, cooked, or pounded plus cooked. In meat, DIT in relation to meal energy was reduced by ~40% due to pounding or cooking and 57% due to pounding plus cooking, with the savings occurring primarily through decreases in the duration of the DIT response. In tubers, DIT was reduced by 35% due to pounding, 40% due to cooking, and 51% due to pounding plus cooking, with the savings driven by decreases in duration and the activity associated with food ingestion. Assuming that meat and tubers were major caloric resources for ancestral hominins, energetic savings of this magnitude imply that habitual food processing could have increased dietary net energy gain by up to 8% due to DIT-related mechanisms alone. Our results support the conclusion that reductions in DIT contribute meaningfully to energy gains associated with processed diets, providing new insights into the evolution and maintenance of human energy budgets.
This research was generously funded by fellowships and grants from the National Science Foundation (GRFP and DDIG BCS-0962038), L.S.B. Leakey Foundation, and Department of Human Evolutionary Biology at Harvard University.