What is Homeostasis?
Homeostasis is
the body's ability to maintain a stable internal environment. Introduced by Claude
Bernard in 1854, this concept includes:
- Body temperature regulation
- pH balance
- Energy balance
Understanding
Bioenergetics
Bioenergetics is the study of how energy flows in
living organisms. The body maintains energy balance through:
- Energy Intake – Calories from food and the
amount consumed
- Energy Expenditure – Energy used for physical
activity and internal heat production
Internal heat
includes:
- Basal Metabolic Rate (BMR) – Energy required for vital
functions at rest
- Thermic Effect of Food – Energy needed for digestion
and storage
Energy Imbalance and
Weight Changes
When energy
intake and expenditure are not equal, imbalances occur:
- Excess energy intake → Stored as fat → Leads to
weight gain
- Insufficient energy intake → Weight loss due to under-eating,
digestive disorders, or disease
Measuring Energy:
Calories vs. Joules
The International
System of Units (SI), established in 1960, standardized energy measurement:
- Joule (J) / Kilojoule (kJ) – Used in most countries
- Calorie (Cal) / Kilocalorie
(kcal)
– Common in the U.S. and EU food labels
- 1 Cal = 1 kcal = 4.2 kJ
- 1 Calorie raises the temperature of 1
kg of water by 1ºC
The calorie was
first used in nutrition by Nicholas Clément in 1824, though its exact
origins are debated.
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