Differential effects of heat in the phases of the light-dark cycle in the activity-based anorexia model.

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This research builds on the studies on ambient temperature as a key influence in the recovery of rodents exposed to the activity-based anorexia (ABA) model. The ABA model is an experimental paradigm in which rodents under a restricted feeding schedule and with free access to an activity wheel show signs that parallel those of anorexia nervosa in humans. The present study focuses on the effects of applying heat during the different phases of the dark-light cycle in the activity levels, body weight, food intake, body temperature, and recovery rates of 30 male rats submitted to ABA. After reaching a 20% weight loss criterion, animals were randomly assigned to three experimental conditions: (a) continuous warming, (b) warming exclusively during the light phase, or (c) warming exclusively during the dark phase. Differential effects were found depending on the modalities of warming: in comparison with either light or dark warming, continuous warming significatively decreased activity, facilitated weight gain, and maintained body temperature. Transient effects of warming were found both in the groups warmed either during light or dark periods exclusively. The results suggest that both light and dark warming did not promote recovery in animals exposed to ABA. Evidence about the beneficial effects of continuous warming are in line with previous research and reinforces adding external heat as a useful tool in the treatment of anorexia nervosa.