Through this study, it was shown that an 8 week 20% CR diet reduced body weight significantly. Likewise other studies have shown the significant decreasing effect which CR causes on body mass (Selman et al., 2005). This can be explained by the loss in LM and FM.

Body composition

Previous studies also found CR induced a significant reduction in both LM and FM. Redman et al. (2008) reported that visceral and subcutaneous fat mass deposits, as well as lean mass, are decreased during episodes of CR. A factor to consider is that the DXA may have missed changes to specific fat masses, as the location of the fat mass was not used in the analysis.

 

RMR

The RMR was significantly alleviated from BL to week 8 measurements. These findings correspond with previous data ( Ferguson et al., 2007). The problem lies with discerning whether the RMR of the mice was reduced by the CR, or if it was simply an effect of the decline in BM. This study found there to be a significant effect of BM on RMR. Work by Hempenstall et al. (2010) disagreed with this data, finding that BM had no effect on RMR. Varying conclusions among other studies could be explained by the experimental procedures followed. The length and percentage of CR diet must also be taken into account. It is the fact that many studies use different protocol, which leads to a noticeable lack of census on how CR affects metabolic rate (Speakman et al., 2002; Masoro, 2005).

Body Temperature

The reduction in Tb during CR is usually associated with a decline in RMR. Body temperature had no effect on the RMR, whereas Redman et al. (2008) reported that a reduction of Tb often coincides with a decrease in RMR. When looking at Tb, it is perhaps important to consider the strain of mouse used in this study.Other work found strain variation in the Tb of 28 types of mice (Rikke, et al., 2002).

Activity

Looking at the total daily activity did not show any change from BL to week 8 measurements. This was probably due to the fact that mice exhibit different levels of activity depending on the time of day (Mendoza, 2007), so it could be that measuring total daily activity is too general. Total dark activity during BL was a lot higher than the levels of activity recorded in the light phase. Previous published data has reported that prior to CR, high activity is shown primarily in dark phases (Holmes and Mistlberger, 2000). This is explained by the nocturnal lifestyle of mice. The change in BM had an effect on total dark activity. These results work in accordance with studies by Challet et al (1997). Nocturnal components of activity rhythms are markedly increased during CR, and with a lower BM (Challet et al., 1997).

The total light activity showed that there was a significant increase during 20% CR diet. One reason for this could be the influence of food anticipatory activity (FAA) occurring 3 hours prior to feeding, which would coincide with the light phase during the CR diet.

This study found the food anticipatory activity (FAA) increased over the course of the experiment. This is backed up by other studies which came to the same conclusion (Gutman et al., 2007; Mendoza, 2007). It appears that as the mice in this study underwent CR, the diet caused a shift in meal time behaviour.The changes imposed by circadium rhythms should be incorporated into further studies, as to provide a clearer perspective on activity changes.