Animals

61 C57/BL6 male mice were used during this study. The mice were maintained on a 12:12h light/dark cycle, with lights on at 0500 hr. For a 2 week period, known as baseline (BL), body mass (BM) and food intake (FI) were recorded on a daily basis. Following on from this the mice were placed on a diet 20% of their average food intake. Over the next 8 weeks their weight was recorded, and several measurements taken:

Resting metabolic Rate

Resting metabolic rate (RMR) was measured during week 1 of BL and following 8 weeks of 20% CR using open-flow respirometry. Temperature controlled incubators were set up containing airtight Plexiglas chambers. Mice were weighed (±0.01g) before being placed in individual chambers. Readings of the O² consumption were measured over the space of 3 hours.

Dual Energy X-ray Absorptiometry (DXA)

During the BL period and week 8 of 20% CR, body composition of the mice was determined by the use dual-energy X-ray absorptiometry. Total lean mass and total fat mass were calculated with this method.

Transmitter Data

Body temperature (Tb) and activity were monitored with the use of internal transmitters (transponders) running off the system VitalView™(Harkin, 2002). The animals’ cages were placed on a pad which contained receivers. Data collection was stopped and analysed on a weekly basis.

Statistical Analysis

Statistical analyses were performed using SPSS ( SPSS Inc., USA, version 18) and Minitab Inc., PA, USA, version 15) statistical software.