Self-Starvation in the Rat: Running versus Eating

Abstract

Rats given the combination of unrestricted access to an activity wheel and restricted access to food can lose weight to the extent that they will die unless removed from these conditions. Although this has been known for forty years, why this happens has remained unclear. The phenomenon is paradoxical in that one might expect such rats to eat more as their weight decreases, but in fact they eat less than resting controls. This lecture first examines some of the factors than influence whether self-starvation will occur, such as age, time of food access, type of food and ambient temperature. It then compares competing explanations such as circadian adaptation, thermo-regulation and food aversion learning. As so often in psychology, it turns out that selfstarvation results from a combination of many separate factors. The general implications of this research are examined, including whether it provides a useful animal model for human anorexia nervosa. Keywords: self-starvation, rats, anorexia nervosaLas ratas sometidas simultáneamente a restricción de comida y acceso a una rueda de actividad pierden peso hasta el extremo de morir si no son retiradas a tiempo de estas condiciones. Aunque este hecho es conocido desde hace cuarenta años, la razón por la cual esto sucede permanece sin resolver. Lo paradójico de este fenómeno reside en que, aunque sería esperable que las ratas comiesen más a medida que su peso disminuye, en realidad estos animales comen menos que sus controles sedentarios. En esta conferencia se examina, en primer lugar, algunos factores que influyen en el desarrollo de la auto-inanición como son la edad, el tiempo de acceso a la comida, el tipo de comida y la temperatura ambiental. A continuación se comparan algunas explicaciones tales como la adaptación del ritmo circadiano, la termorregulación y la aversión adquirida a la comida. Tal como ocurre con frecuencia en psicología, la auto-inanición es el resultado de diferentes factores. Finalmente, se examinarán algunas implicaciones más generales de esta investigación, incluida su posible utilidad como modelo animal para el estudio de la anorexia nerviosa en humanos. Palabras clave: auto-inanición, ratas, anorexia nerviosa

Physical activity: benefit or weakness in metabolic adaptations in a mouse model of chronic food restriction?

“…Finally, the low EE described in both FR and FRW mice, especially during the light period when only FRW showed FAA, led us to conclude that EE not only was related to exercise but reflected an adaptive way to save energy to maintain physiological functions. The impact of food restriction on energy metabolism confirmed data obtained with 30% of food restriction (8). However, the strategy used by FR and FRW mice were different.…”

“…Regarding self-starvation as part of a cognitive/emotional aspect of the disease proved difficult, even impossible, to mimic in mice. Indeed, in the ABA model, the self-starvation, which is not always observed (36), might be related to physiological adaptations to maintain thermogenesis and to compensate for the dryness of the pellets since the presentation of humidified pellets during the 2-h time-restricted feeding or an increasing of the room temperature led to the disappearance of the voluntary food restriction (7,8). These data support more adaptations to physiological changes than a cognitive drive to reduce feeding.…”

An evolutionary model of low mood states

“…Food restriction in animals, for example, leads to an increase, not a decrease, in energy expenditure (Boakes, 2007;Routtenberg and Kusnezov, 1967), and increased rather than decreased risktaking in terms of coming out of cover in the presence of predators (Krause et al, 1998). Food-restricted animals of many different species also switch from preferring less variable to more variable food sources (Caraco et al, 1980;Kacelnik and Bateson, 1996), in line with the predictions of risk-sensitive foraging theory (Stephens, 1981).…”

Ghrelin: Central and Peripheral Implications in Anorexia Nervosa

“…However, as specified by Klenotich and Dulawa (2012), the ABA paradigm is strongly dependent upon factors that amplify or reduce some parts of the phenotype, i.e., the choice of rodent strain (more or less resistant to ABA, Gelegen et al, 2007), the sex of animal (female are more vulnerable to ABA), the age (younger animals are more susceptible to ABA), the temperature (increasing the temperature to 32°C strongly reduces the ABA behavior, Cerrato et al, 2012), the time of the day the animals receive food, and the hydration/dryness of the food. In fact, Boakes and Juraskova, 2001; Boakes, 2007) demonstrated that the “self-starvation” observed in ABA rats might reflect both the reduced palatability of the dry chow for a dehydrated animal and satiety signals from a stomach full of water. Thus, giving hydrated food during the 1 h-feeding schedule completely abolishes the ABA phenotype (rapid weight loss, hyperactivity, etc.).…”