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Enthalpy changes and heat production induced by a meal
1Department of Physiology, Odense University, Denmark.
European Journal of Clinical Nutrition
|September 1, 1989
Summary
Re-analysis of 1974 calorimetry data reveals only 20% of ingested glucose and amino acids were combusted within 2.5 hours. The remaining substrate was stored, likely as chemical energy, with 40% of energy lost as heat.
Area of Science:
- Metabolic studies
- Nutritional science
- Thermodynamics
Background:
- Pittet and colleagues' 1974 study measured the thermic effect of glucose and amino acids.
- Direct and indirect calorimetry were employed to assess energy expenditure and substrate utilization.
Purpose of the Study:
- To re-analyze the 1974 calorimetry data.
- To determine substrate combustion and energy storage within 2.5 hours of ingestion.
Main Methods:
- Re-analysis of existing direct and indirect calorimetry data.
- Calculation of substrate combustion percentage.
- Assessment of heat loss and energy storage.
Main Results:
- Only approximately 20% of ingested substrate (glucose and amino acids) was combusted within the 2.5-hour observation period.
- Indirect calorimetry indicated a change in enthalpy due to combustion.
- Direct calorimetry demonstrated that about 40% of the energy was lost as heat or stored in the body.
Conclusions:
- A significant portion of ingested substrate is not immediately combusted.
- The non-combusted substrate is likely stored in chemical form, increasing enthalpy.
- Further investigation is needed to elucidate the exact form of energy storage.