Studies of Food Intake: Lessons from Nontraditionally Studied Species

Conclusions

The examples given above across a wide range of species indicate that “experiments of nature” afford scientists of ingestive behavior opportunities to obtain a different, and frequently telling insight into the diversity of this behavior. We selected examples of species that naturally exhibit features of ingestive behavior that are often studied in the laboratory through significant and often highly invasive physiological manipulations performed on more traditional species (rats and mice) or via genetic engineering or selective breeding of these species. We hope that the reader of this trek through the control of food intake across diverse regions of the animal kingdom might more fully appreciate the wide range of feeding strategies and physiological responses of these nontraditionally studied species. Although it is often the view that the ingestive behavior responses of laboratory rats and mice are the “gold standard” by which all others should be compared, it could be just as easily argued that these domesticated and inbred animals are the oddities because of the lack of evolutionary pressures shaping their ingestive and other behaviors/physiology during the last ∼100 years of captive breeding. As always, perspective is in the eye of the beholder.

In summary, several points can be drawn from the food intake responses of the species reviewed here in terms of the use of these various species for research on ingestive behaviors: (1) there are naturally occurring fasts of prolonged duration or more modest reductions in food intake that could offer insight into satiety mechanisms, (2) glucoprivation and lipoprivation are not uniformly stimulators of food intake, (3) there are naturally occurring instances of resistance and susceptibility to HFD-induced obesity that seem to make sense given the animals’behavioral ecology, and (4) perhaps a reason for the ever-expanding list of peptides that stimulate or inhibit food intake is that some may function to draw animals to or away from food (appetitive) (i.e., by affecting foraging and other food-seeking behaviors), rather than affecting ingestive (consummatory) behavior directly. Thus, by studying the differences in physiological responses to the same experimental treatment across a wide range of species, we are able to gain valuable perspective on the organization of energy balance systems, the relative importance of specific sensory input signals, as well as other environmental factors that may modify food ingestion in real-world situations.