The thermoneutral zone- Can we use ambient temperature to aid health

Our energy expenditure has three major components; the thermic effect of physical activity, the thermic effect of feeding, and the resting metabolic rate (RMR). This RMR is a basal use of energy for the body to maintain basic functions, such as homeostatic mechanisms. There is a long-established relationship between ambient temperature and energy expenditure. The range of temperatures where the body naturally maintains its optimum temperature is the thermo-neutral zone (TNZ). This is said to be around 22 °C when light clothing is taken into consideration, and within the individual is determined by insulation, body composition, genetics, and long-term residential environment. Thermo-regulation - an active homeostatic mechanism by which optimum body temperature is maintained - must be employed outside of the TNZ. Previously, mild cold exposure (19 °C) has been shown to induce a ~6% increase in energy expenditure compared to the thermo-neutral (24 °C) control[1]. This corresponded to ~120 kcal/day increase; similar prolonged changes in energy balance have been shown to effect gradual weight change[2]. Modern lifestyle, often revolving around office environments and related environmental control, limit exposures to temperature ‘extremes’ outside of the TNZ. This could limit energy expenditure, complicating weight management in already low-ambulatory jobs. Similarly, increased energy expenditure hypothesized to occur in cold or poorly insulated housing could drive compensatory increases in appetite and subsequent weight management issues. This study aims to define the TNZ of New Zealand based individuals (protocol one). The TNZ will be used to establish the effect and feasibility of minor decreases or fluctuations in ambient temperature as an intervention to increase energy expenditure and aid in weight management (protocol two). This is pertinent as the only alternative, safe way of increasing energy expenditure is increased physical activity, which is not always an option. Along with continuous physiological measures and body composition information, we may also be able to establish models to determine individual TNZ ranges and energy expenditure under known conditions. This study will provide potential interventions regarding the obesity epidemic and weight management with New Zealand specific parameters, and suggest a method for its application elsewhere. It may also advise the public health sector as to a further effect of cold housing on physical health. [1] Celi FS, Brychta RJ, Linderman JD, Butler PW, Alberobello AT, Smith S, Courville AB, Lai EW, Costello R, Skarulis MC, Csako G. Minimal changes in environmental temperature result in a significant increase in energy expenditure and changes in the hormonal homeostasis in healthy adults. European journal of endocrinology. 2010 Dec 1;163(6):863-72. [2] Hill JO, Wyatt HR, Reed GW, Peters JC. Obesity and the environment: where do we go from here?. Science. 2003 Feb 7;299(5608):853-5.