<b><i>Introduction:</i></b> Humans are known to adapt to external temperature variations by altering energy intake, expenditure, and body fat storage for insulation [<xref ref-type="bibr" rid="ref1">1</xref>, <xref ref-type="bibr" rid="ref2">2</xref>]. However, it is not clear whether the temperature of ingested water would induce such effects. Similarly, the involvement of the temperature of the ingested beverage has not been addressed in terms of body weight changes [<xref ref-type="bibr" rid="ref3">3</xref>]. <b><i>Objectives:</i></b> This study was to investigate the effect of the ingestion of plain or sweetened water with varied temperatures on growth measures of rats. <b><i>Methods:</i></b> Approval was obtained from the Institutional Animal Care and Use Committee of the American University of Beirut. After a 1-week adaptation period, 5- to 6-week-old male Sprague-Dawley rats were randomly divided into their respective experimental groups, housed individually (22 ± 1°C, reverse light cycle 12:12 h dark/light, light off at 10:00 a.m.) with free access to food and beverage for 8 weeks. <b><i>Experiment 1 (Plain Water):</i></b> Two groups of rats (<i>n</i> = 9) consumed room-temperature [∼22°C] (NW) or cold [∼5°C] (CW) water. <b><i>Experiment 2 (Sweetened Water):</i></b> Four groups of rats were offered sweetened water for 12 h, followed by plain water; (1) 10% sucrose + cold temperature (CS, <i>n</i> = 7), (2) 10% sucrose + room temperature (NS, <i>n</i> = 8), (3) 0.05% acesulfame K + cold temperature (CA, <i>n</i> = 7), and 4) 0.05% acesulfame K + room temperature (NA, <i>n</i> = 8). Food and beverage intake, body weight, and body composition were monitored using NMR minispec (LF110 Body Composition Analyzer, Bruker, USA) and energy expenditure was calculated based on the equation developed by Ravussin et al. [<xref ref-type="bibr" rid="ref4">4</xref>]. Significance was set at a <i>p</i> value <0.05. <b><i>Results:</i></b> Experiment 1: Body weight changes were similar between groups (Fig. <xref ref-type="fig" rid="f01">1</xref>-Exp 1a). In the CW group, lean body mass (%) was significantly higher, while body fat (%) was lower than the NW (Fig. <xref ref-type="fig" rid="f01">1</xref>-Exp 1b, c). These changes may relate to the calculated total energy expenditure [NW: 66.73 ± 4.49 kcal/day and CW: 73.75 ± 3.92 kcal/day) (<i>p</i> value = 0.003) since energy intake (NW: 89.97 ± 7.63 kcal/day vs. CW: 93.29 ± 6.26 kcal/day, <i>p</i> value = 0.329) was similar between groups. Experiment 2: Body weight of the CA group was higher than that of the other groups (Fig. <xref ref-type="fig" rid="f01">1</xref>-Exp 2a). Lean body mass (%) of the sucrose-sweetened water groups (Fig. <xref ref-type="fig" rid="f01">1</xref>-Exp 2b, c) was significantly higher, while body fat (%) was lower than that of the non-caloric sweetened water groups; these were not affected by the temperature of the beverage. Those variations are mostly explained by the differences in energy expenditure (<i>p</i> value temperature × sweetener = 0.015), as energy intake was not significantly different between groups. <b><i>Conclusion:</i></b> Cold plain water decreased body fat and increased lean body mass with no effect on total body weight. Sucrose-sweetened water had a better impact on body composition irrespective of the temperature of the beverage. The beneficial effects are mainly due to increased energy expenditure rather than variations in energy intake. Thus, the energy cost of warming the water seems to have been derived from an increase in fat oxidation.
Mice long-term selected for high body mass are more susceptible to body fat deposition in response to a high fat diet due to insufficient increase in heat production
