Surely we have all wondered at some point how much energy our body needs for everything to function properly. The great machine we call “our body” works well when we manage to meet the vast majority of its needs, and it just so happens that energy is one of the most important requirements for it to function correctly.
Our energy needs are studied under the term Total Energy Expenditure (TEE), which strongly conditions energy balance — a factor that affects processes such as weight gain or weight loss. TEE is highly variable between individuals. This is due to the large number of variables that influence energy expenditure, such as physical exercise, temperature, sleep duration, increased requirements (growth, pregnancy, lactation…), and basal energy expenditure (BEE). All of these are more or less important and sound familiar to us, but BEE alone represents between 60–70% of TEE.
For this reason, I am going to focus on it. What is BEE? Basal energy expenditure is defined as the energy required to carry out vital functions while we are in a state of rest. There are many determinants that can influence this resting energy expenditure, such as fasting, alcohol intake, nicotine use, caffeine intake, vigorous endurance exercise, environmental conditions, collection devices, number of measurements over 24 hours, variation in repeated measurements, and the respiratory quotient, among others.
Today, we have a wide range of techniques that are used to obtain a more or less accurate estimate of basal energy expenditure:
- Predictive equations: these consist of calculations that can provide an approximate estimate of resting energy expenditure. The Harris–Benedict equation is the most widely used technique in clinical practice, although many others exist. This formula is one of those integrated into today’s smart scales (bioelectrical impedance).
- Direct calorimetry: this is a rarely used technique in which airtight rooms with insulated walls are used to measure the heat released. The most well-known example is the Atwater chamber, but due to its complexity it is only used in research.
- Indirect calorimetry: in this type of technique, the aim is to measure residual molecules from our metabolism (the amount of CO₂ released and water) and oxygen consumption. However, this technique only measures the by-products of carbohydrate and fat metabolism, not protein metabolism, leaving a significant fraction of energy unaccounted for. To determine this latter component, a measurement of urinary nitrogen would be required and added to the results of this technique.
All these estimates of basal energy expenditure, together with other variables that influence it, allow professionals to adapt each person’s lifestyle in order to perfectly meet their needs in relation to their goal, such as weight gain or weight loss.
Even so, to improve BEE, professionals have a few other “aces up their sleeve”. There are certain foods capable of slightly stimulating BEE thanks to the presence of specific nutrients in their composition. Spicy foods (specifically the compounds responsible for the sensation — capsaicin and capsinoids) are among the substances with the strongest scientific evidence, having been shown to significantly increase energy expenditure compared to placebo. This is because one of their targets is the activation of metabolic pathways related to thermogenesis (heat production), involving both proteins such as UCP1 and genes associated with the TRP–SNS–UCP1 pathways.
Another food with a solid scientific basis capable of increasing resting energy expenditure is green tea. This is due to its catechin content — molecules capable of regulating energy expenditure. There are hypotheses regarding its mechanism of action, but it is not yet fully understood.
It should be noted that these foods do not have a dramatic effect, but they do exert a measurable impact which, together with exercise and good nutrition, can greatly support weight management. Furthermore, given all the individual factors that influence energy expenditure, along with the involvement of specific genes in these pathways, an individualised assessment is necessary to determine which strategies are most appropriate for each case.
References:
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- Palmer BF, Clegg DJ. Strategies to Counter Weight Loss-Induced Reductions in Metabolic Rate. Curr Sports Med Rep. 2019 Jul;18(7):258–265. doi: 10.1249/JSR.0000000000000610.
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- Blasco Redondo R. Resting energy expenditure: assessment methods and applications. Nutr Hosp. 2015 Feb 26;31 Suppl 3:245–254. doi: 10.3305/nh.2015.31.sup3.8772.
