Did you know that a higher core body temperature burns additional calories? For over 100 years scientists have noted the relationship between core temp and resting metabolic rate (the number of calories burned while at rest). While at rest, approximately half of the calories the body burns is for the purpose of maintaining core temperature. This is one of the many processes that the body uses to maintain stable physiological functions.
Core temp set point
Each person has a core temperature “set point” – a temperature at which their body will try to maintain. The average set point is the well-known 37° C/98.6° F. However, this can be higher or lower for each individual, and even within a day that resting temperature varies by 0.5°C/1.0°F due to the circadian cycle. For menstruating women, this daily temperature varies by the phase of their menstrual cycle.
The core temp set point is controlled by the brain’s hypothalamus. When the core temp varies from this set point, a complex chemical process starts, signaling the body to either preserve heat and increase heat production (when core temp is too low), or to release heat and slow heat production (when core temp is too high).
Higher and lower metabolic rates
The core temp set point gives a simple explanation for why people who live in cooler environmental temperatures have higher resting metabolic rates – their body needs to generate more heat to maintain core temp, and does so by burning calories. This effect, can, of course, be counteracted by behavioural changes, such as wearing warmer clothes (which eliminates the need to generate more heat).
Conversely, core temperature drops when too few calories are consumed. The body reacts to this energy deprivation by reducing energy output. This helps explains the well-known phenomenon of resting metabolic rate decreasing under extreme dieting conditions.
Tracking average core temp
The CORE app displays your core temp metrics – daily average, minimum and maximum. The daily average and maximum temperatures are obviously highly influenced by the amount and intensity of sports activity in a day. But the historical temperature data chart can help you identify your core temp while at rest.
When you wear your CORE sensor continuously and closely observe this data, you may note there is a range of core temps that accompany the general term “rest”. You may note different core temps while sleeping, lying down watching television, sitting reading a book, sitting and typing, and standing in place. These temperature changes all correspond to the slightly different energy requirements of each activity, even though they may all be considered “rest”.
For those trying to actively manage their weight, paying attention to this daily and weekly core temp data may provide valuable insights. In general, a higher core temperature will result in a higher metabolic rate, meaning more calories are being burned.
The interplay amongst core temperature, metabolic rate, and energy balance is complex. A good starting point for further reading is the paper Body temperature: Its regulation in framework of energy balance.
András Garami & Miklós Székely (2014) Body temperature, Temperature, 1:1, 28-29, DOI: 10.4161/temp.29060