Hyperphagia: A Necessary Precondition to Obesity?

Weight-gain is generally attributed to a caloric imbalance resulting from hyperphagia. However, this attribution is often made without observing caloric intakes during the initial accumulation of fat stores. Instead, this conclusion is drawn because many obese organisms overeat, and overconsumption is sufficient to cause weight-gain. The literature is reviewed, specifically those studies on the onset of caloric overconsumption relative to weight-gain and the accumulation of fat during food restriction, which suggests that hyperphagia is not necessary for animals prone to obesity to become fatter and heavier. It is observed that animals with genetically-and surgically-induced obesity often become fat prior to hyperphagia and continue to gain even if food restricted to subnormal levels. Overconsumption does speed this gain.