What do we spend energy on?

What we spend our energy on is a vital question that has significant implications for our health and well-being. Energy expenditure is a complex phenomenon that involves three main factors: basal metabolism, the thermic effect of food, and physical activity. Basal metabolism refers to the energy required to maintain vital bodily functions at rest. The thermic effect of food is the energy expended in digesting, absorbing, and metabolizing food. Physical activity includes any movement that causes energy expenditure and can be divided into exercise activity thermogenesis (EAT) and non-exercise activity thermogenesis (NEAT). 

Research has shown that basal metabolism accounts for the majority of daily energy expenditure, approximately 60-70%, while the thermic effect of food accounts for only about 8-15% (Aragon et al. 2017). Physical activity makes up the remainder contributing to energy expenditure.

The amount of energy expended on physical activity varies significantly between individuals. While exercise activity thermogenesis accounts for approximately 15-30% of total energy expenditure, non-exercise activity thermogenesis can vary by as much as 15-50% (Aragon et al. 2017). Individual differences in physical activity and especially in non-exercise activity thermogenesis may explain why some people are overweight, and others are not. Those who are more active in their daily lives tend to be leaner.

The importance of physical activity for maintaining a healthy weight cannot be overstated. While a single exercise session does not consume significant energy, regular physical activity has positively impacted daily energy expenditure. Strength training, for example, can increase daily energy expenditure by 60-360 kcal, while endurance exercise can consume 150-700 kcal.

In conclusion, energy expenditure is a complex phenomenon that involves multiple factors, including basal metabolism, the thermic effect of food, and physical activity. Although basal metabolism and the thermic effect of food make up the majority of daily energy expenditure, physical activity is essential and, in some individuals, can have a major impact on maintaining a healthy weight and overall health. Incorporating regular physical activity into our daily lives can increase our energy expenditure and improve our health and well-being.

References

Aragon, A. A., Schoenfeld, B. J., Wildman, R., Kleiner, S., VanDusseldorp, T., Taylor, L., ... & Stout, J. R. (2017). International society of sports nutrition position stand: diets and body composition. Journal of the International Society of Sports Nutrition, 14(1), 16.

Caspersen, C. J., Powell, K. E., & Christenson, G. M. (1985). Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public health reports, 100(2), 126-131.

Hall, K. D., Heymsfield, S. B., Kemnitz, J. W., Klein, S., Schoeller, D. A., & Speakman, J. R. (2012). Energy balance and its components: implications for body weight regulation. The American journal of clinical nutrition, 95(4), 989-994.

Levine, J. A. (2007). Nonexercise activity thermogenesis–liberating the life-force. Journal of Internal Medicine, 262(3), 273-287.

Ravussin, E., Lillioja, S., Anderson, T. E., Christin, L., & Bogardus, C. 1986. Determinants of 24-hour energy expenditure in man. J Clin Invest, 78(6), 1568-78.