5.0: Introduction

When Calories Become Clues: What Thermochemistry Teaches Us About Healing and Nutrition

                                    

Figure \(\PageIndex{1}\): A graphic with basic facts about Carla Prado, Brazilian-born nutritionist who uses whole body calorimetry to study how different health conditions affect how the human body uses and expends energy. Dr. Prado then uses this information to suggest nutritional tactics to aid recovery. Image from University of Alberta; copyright 2025 University of Alberta.

Thermochemistry explores the energy changes that accompany chemical and physical processes. Every transformation, from the synthesis of a molecule to digestion of your lunch, involves the exchange of heat. In many cases, the energy produced by a reaction is more important than the products formed.  For example, in fuel combustion, our goal is often to extract as much usable energy as possible to power other systems. Thermochemical principles help us understand how energy is transferred, what it tells us about a system, and how we can harness it.

Later in this chapter, we will discuss calorimetry, a technique used to measure heat flow. While it is often applied to chemical reactions or heat transfer between objects of different temperatures, calorimetry also has applications in human health. Dr. Carla Prado, a Brazilian-born nutritional scientist and expert in body composition and metabolism, uses a technique called whole-body calorimetry to investigate how people with different health conditions expend energy.

Whole-body calorimetry chambers measure the heat exchanged by the body to determine someone’s metabolic rate. These chambers precisely monitor oxygen consumption, carbon dioxide production, and thermal output, converting these physical data into an energy profile of the person inside. Prado and her research group then use this information to study the effect of different conditions on the body and guide the design of nutritional interventions to improve patient recovery. Her research group has applied this process to patients with cancer, chronic illness, obesity, and, most recently, postpartum women. Prado’s work has shown that postpartum women, especially those who have undergone C-sections, often face significant nutritional and energy challenges that traditional guidelines overlook.

Figure \(\PageIndex{2}\): Photo of one of the whole body calorimeter rooms at the University of Alberta's Human Nutrition Research Unit. While it looks mostly like a regular room, it is sealed and connected to an air flow system that flushes "fresh air" through for precise monitoring of oxygen consumption and carbon dioxide production by the person inside. The room also possesses specialized ports for blood draws or food passage that minimize the loss of air from the room. Participants can be monitored precisely for longer periods of time, both at rest and while conducting physical activity. Image from University of Alberta; copyright 2025 University of Alberta.

By applying the laws of thermochemistry to human metabolism, Dr. Prado’s research has helped shape personalized nutrition plans that reduce complications, support healing, and improve long-term health outcomes. Her work is a striking example of how enthalpy, energy balance, and calorimetry are more than abstract concepts—they are tools that can transform healthcare and quality of life. In this chapter, we will explore the same core principles that underpin Prado’s research: energy, enthalpy, and calorimetry, with a focus on their role in chemical transformations.

Sources:

1. Carla Prado, PhD, RD, FCAHS - [e-mail]. https://apps.ualberta.ca/directory/person/cprado.
2. Da Silva, B. R.; Pagano, A. P.; Kirkham, A. A.; Gonzalez, M. C.; Haykowsky, M. J.; Joy, A. A.; King, K.; Singer, P.; Cereda, E.; Paterson, I.; Pituskin, E.; Thompson, R.; Prado, C. M. Evaluating Predictive Equations for Energy Requirements throughout Breast Cancer Trajectory: A Comparative Study. Clinical Nutrition 2024, 43 (9), 2073–2082. https://doi.org/10.1016/j.clnu.2024.07.032.
3. Ford, K. L.; Quintanilha, M.; Trottier, C. F.; Wismer, W.; Sawyer, M. B.; Siervo, M.; Deutz, N. E. P.; Vallianatos, H.; Prado, C. M. Exploring Relationships with Food after Dietary Intervention in Patients with Colorectal Cancer: A Qualitative Analysis from the Protein Recommendations to Increase Muscle (PRIMe) Trial. Support Care Cancer 2024, 32 (7), 418. https://doi.org/10.1007/s00520-024-08620-1.
4. Pereira, L. C. R.; Elliott, S. A.; McCargar, L. J.; Bell, R. C.; Vu, K.; Bell, G.; Robson, P. J.; Prado, C. M. The Influence of Energy Metabolism on Postpartum Weight Retention. The American Journal of Clinical Nutrition 2019, 109 (6), 1588–1599. https://doi.org/10.1093/ajcn/nqy389.
5. PradoLab. https://www.drcarlaprado.com/.