A theory of activity-based anorexia

Epling, W. Frank; Pierce, W. David; Stefan, Larry

doi:10.1002/1098-108x(198323)3:1<27::aid-eat2260030104>3.0.co;2-t

Cited by 161 publications

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“…In the laboratory, rats on food restriction with the opportunity to (wheel) run show activity anorexiaFa vicious cycle of suppressed food intake, declining body weight and escalating wheel activity leading to starvation and death. 8,9 Compared with lean strains, rats from an obese-prone strain survive longer and show less reactivity to food restriction and wheel running. 10 Food restriction and intense mobility trigger the hypothalamic-pituitary-adrenal (HPA) axis stress response, increasing hypothalamic CRF expression and circulating concentrations of corticosterone.…”

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Evolution and obesity: resistance of obese-prone rats to a challenge of food restriction and wheel running

et al. 2010

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The adaptive hypothesis that an obese-prone genotype confers a fitness advantage when challenged with food restriction and food-related locomotion was tested using a rat model. Juvenile (35-40 days) and adolescent (45-50 days) JCR:LA-cp rats, obese prone (cp/cp) and lean prone ( þ /?), were exposed to 1.5 h daily meals and 22.5 h of voluntary wheel running, a procedure that normally leads to self-starvation. Genotype had a dramatic effect on survival of rats when exposed to the challenge of food restriction and wheel running. Although similar in initial body weight, obese-prone juveniles survived twice as long, and ran three times as far, as their lean-prone counterparts. Biochemical measures indicated that young obese-prone animals maintained blood glucose and fat mass, whereas lean-prone rats depleted these energy reserves. Corticosterone concentration indicated that obese-prone juveniles exhibited a lower stress response to the survival challenge than lean-prone rats, possibly due to lower energy demands and greater energy reserves. Collectively, the findings support the hypothesis that an obese-prone genotype provides a fitness advantage when food supply is inadequate, but is deleterious during periods of food surfeit, such as the energy-rich food environment of prosperous and developing societies worldwide. Keywords: adaptation; food restriction; wheel running; genotype; survival Obesity is portrayed as a weight disorder with negative connotations of susceptibility to diabetes, 1 the metabolic syndrome, 2 heart disease 3 and cancer(s). 4 The modern clinical perspective links obesity to poor health, a shortened life span and to many sociopsychological and lifestyle disorders. An evolutionary perspective, in contrast, views obesity as resulting from variation in genotype and an environment with high-energy-dense food(s). One possibility is that the obese-prone genotype is nonadaptiveFresulting from a coincidence of genetic drift and the high-energy foods of modern humans.5 Alternatively, the obese-prone genotype may be a consequence of adaptation, and obesity is a phenotypic expression of an interaction between genotype (obese-prone vs lean-prone) and environment (high-/lowenergy food supply). The 'thrifty gene' theory of obesity is one form of the adaptive hypothesis. The theory explains how genes favor the efficient use of energy stores in times of feast followed by famine, and result in obesity in the food-rich environment of prosperous societies.6,7Our formulation of the adaptive hypothesis proposes that the obese-prone genotype confers an advantage under conditions of unpredictable changes in food supplyF allowing for storage and conservation of energy and increased foraging during periods of food depletion. In the laboratory, rats on food restriction with the opportunity to (wheel) run show activity anorexiaFa vicious cycle of suppressed food intake, declining body weight and escalating wheel activity leading to starvation and death. 8,9 Compared with lean strains, rats from an obese-prone strain surviv...

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Evolution and obesity: resistance of obese-prone rats to a challenge of food restriction and wheel running

et al. 2010

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“…The phenomenon, labelled activity anorexia (7), is characterized by dramatic increases in activity paradoxically associated with decreased food consumption, and has also been observed in some humans diagnosed with anorexia nervosa (10,15,27) as well as some athletes (14,23,26,28). These observations have led researchers (7,9) to suggest that activity anorexia, induced experimentally in rodents, might serve as a useful model for the understanding of anorexia nervosa and its treatment in humans.…”

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An analysis of excessive running in the development of activity anorexia

Beneke

Schulte

Tuig

1995

Physiology & Behavior

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analysis of excessive running in the development of activity anorexia. PHYSIOL BEHAV 58(3) 451-457, 1995.--Food restriction combined with activity wheel access produces activity anorexia: a combination of excessive running, reduced food intake and rapid weight loss. Temporal distributions of running in activity anorexia were examined in a reversal design with one of 2 × 2 × 2 factorial combinations (pelleted-vs-powdered food × deprivation × wheel access) as the treatment condition. Wheel revolutions were recorded in 30 min intervals; body weights, food and water intakes were measured daily. Only wheel access combined with food deprivation reliably produced activity anorexia. Excessive running occurred in the absence of schedule-induced polydipsia, was unaffected by food form, and showed distributional characteristics of facultative behavior. These results are inconsistent with schedule-induced behavior explanations. Running distributions appeared consistent with chronobiological models with light/dark onset and feeding serving as zeitgebers. Activity anorexia Activity Temporal running distribution Food deprivationSchedule-induced behavior Rats RATS (8,13,20,21), mice (8), and golden hamsters (4,5) allowed access to running wheels combined with food deprivation schedules (60-90 min daily food access), ran excessively, ate little and eventually starved. The phenomenon, labelled activity anorexia (7), is characterized by dramatic increases in activity paradoxically associated with decreased food consumption, and has also been observed in some humans diagnosed with anorexia nervosa (10,15,27) as well as some athletes (14,23,26,28). These observations have led researchers (7,9) to suggest that activity anorexia, induced experimentally in rodents, might serve as a useful model for the understanding of anorexia nervosa and its treatment in humans. Consistent with this notion, Epling and Pierce (7) also observed dramatic increases in running immediately before and after scheduled feeding. They suggested that the running might be a schedule-induced behavior. If water is continuously available during a variable interval schedule of food reinforcement, rats become polydipsic, drinking several times their normal daily water intake (11). The behavior typically manifests itself as an interim schedule-induced behavior, as described by Staddon (24), and has also been obtained with fixed time schedules of reinforcement [e.g., (25)]. If one were to postulate water availability as somewhat analogous to availability of a running wheel, then one could also postulate the excessive wheel running as scheduleinduced under the same conditions that produce schedule-induced polydipsia (17,25). Although studies of schedule-induced behavior have utilized small food portions as reinforcers and brief (commonly 1 min) periodic schedules, at least by analogy, activity anorexia might be a special case of schedule-induced behavior, or the behaviors might share common underlying mechanisms. If true, variables influencing schedule-induced behavior...

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“…For example, wheel running in rats increases when eating is restricted to a single daily meal (Epling et al, 1983), Such body weight. Yet as body weight decreases, the animal becomes increasingly active on the wheel; that activity, surprisingly, produces a further decline in food intake.…”

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Deprivation and Satiation: The Interrelations Between Food and Wheel Running

Pierce

Epling

Boer

1986

J Exper Analysis Behavior

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Two experiments were designed to assess whether depriving rats of food would increase the reinforcement effectiveness of wheel running (Experiment 1) and whether satiation for wheel running would decrease the reinforcement effectiveness of food (Experiment 2). In Experiment 1, a progressive-ratio schedule was used to measure the reinforcement effectiveness of wheel running when rats were deprived or not deprived of food. Completion of a fixed number of lever presses released a brake on a running wheel for 60 s, and the response requirement was systematically increased until the rat stopped pressing or until 8 hr had elapsed. The ratio value reached (and the total number of lever presses) was an inverted-U function of food deprivation (percentage body weight). In Experiment 2, when wheel running preceded test sessions, fewer food-reinforced lever presses were maintained by the progressive-ratio schedule, and responding occurred at a lower rate on a variable-interval schedule. An interpretation of these results is that deprivation or satiation with respect to one event (such as food) alters the reinforcement effectiveness of a different event (such as access to wheel running).

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A theory of activity-based anorexia

Cited by 161 publications

References 65 publications

Evolution and obesity: resistance of obese-prone rats to a challenge of food restriction and wheel running

Evolution and obesity: resistance of obese-prone rats to a challenge of food restriction and wheel running

An analysis of excessive running in the development of activity anorexia

Deprivation and Satiation: The Interrelations Between Food and Wheel Running

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