Calorie-restricted mice that gorge show less ability to compensate for reduced energy intake

Caloric restriction in mice can trigger gorging behaviour, which is characterized by periods of excessive food ingestion in a short time. Animals that gorge are thought to have a reduced metabolism compared to those that nibble their food over a longer period and might therefore be more able to compensate for reduced energy intake. We examined whether mice that gorged showed less weigh loss during restriction. We placed female mice (n=60) on a restriction of 75% of their ad libitum food intake (FI) for 22 days. FI and body mass (BM) were measured at 1, 2 and 24 h after food provision. Ten controls remained feeding ad lib and we selected the 10 strongest gorgers and 10 strongest non-gorgers for comparison. Mice had BM, FI, resting metabolic rate (RMR), body composition, body temperature, daily energy expenditure (DEE) and circulating levels of the regulatory hormones leptin and ghrelin measured. Gorgers had a significantly lower BM at the end of restriction than non-gorgers or controls, indicating that they were less able to compensate for the reduced energy. Both groups of restricted mice had reduced RMR, however reduced activity was only used as an energy saving mechanism in non-gorgers. Gorging mice had a significantly lower level of circulating leptin than controls and non-gorgers but no differences in ghrelin levels. Gorging mice were, in fact, less able to compensate for reduced energy intake, as they reduced RMR by a similar extent as non-gorgers, but did not reduce activity compared to non-gorgers on the same restriction level. The reduced leptin levels may drive the gorging behaviour.