Metabolism sustains life by generating energy. As energy is generated, variance in temperatures inside a human will occur. As a result, as temperature increases, metabolic rates increase (Clarke 2004). Moreover, the size of an organism (or human), along with temperature, affects the metabolic rate of by different mechanisms. The temperature of an organism, or in the surrounding environment, affects the metabolic rate by increasing the molecular reactions of molecules that have a role in generating energy in the metabolic pathway (Gillooly 2001).
Specifically, animals and humans have varying metabolic rates. Thus, it has been postulated that there have been three different developmental pathways for the development of metabolic processes. For instance, research has shown that perciform fish have not developed a mechanism that allows them to adapt to the cold environment. (Clarke 1999) and human nutrient digestion can vary from person to person. Some individuals can digest calories at a much faster rate than others. Therefore, they are able to generate more energy and heat as a result. It has been postulated that the ability to digest a lot of calories and not put on extra weight can help an athlete perform at a high level because they are able to generate more energy than athletes with slower metabolic rate.
Since metabolism involves generating energy and releasing energy, the measurement of respiration can be used to measure a metabolic rate. The rate of respiration can be used to measure the rate of metabolism because metabolic reactions involve the interactions with water and need ATP to generate energy. ATP is important because it is a product of glycolysis and the TCA cycle. As such, metabolic rates can be measured by the rate of oxygen consumption (Clarke 2004).
There are three explanations for the relationship between the resting metabolic rate and temperature: 1) deterministic-metabolic rate is affected by temperature, 2) indirect-temperature affects metabolic rate and adaptability, 3) no effect-temperature has no influence on resting metabolic rate (Clarke 2004).
This type of research shows that the surrounding temperatures can impact the metabolic rate of organisms and humans.
American College of Sports Medicine: Nutrition and Athletic Performance. Canadian Journal of Dietetic Practice and Research 2000 Winter 61(4):176-192
Clark A. 2004. Is there a Universal Temperature Dependence of metabolism. Journal of Animal Ecology 18; 2:252-256
Clarke Andrew, Nadine Johnston. 1999. Scaling of metabolic rate with body mass and temperature in teleost fish. Journal of Animal Ecology. 68; 5:893-905