>>76365558CICO (Calories In, Calories Out) is real and does align with the laws of thermodynamics, even though the human body is not a perfectly closed system.
Here’s a breakdown:
What’s true:
The human body is not a closed system. It’s an open system that exchanges energy and matter with the environment (through food, heat, work, waste, etc.).
The laws of thermodynamics were originally formulated for idealized systems, but they still apply to open systems like the human body. In fact, thermodynamics has specific equations and principles for open systems, which are widely used in biology and physiology.
What’s false:
Saying "CICO isn't real" misunderstands both the concept of CICO and how thermodynamics works.
CICO is simply a practical expression of energy balance: if you take in more energy than you expend, you store it (usually as fat); if you expend more than you take in, you lose weight. This has been demonstrated repeatedly in metabolic studies.
Important nuance:
CICO is real, but it’s not always simple. Many factors affect both sides of the equation:
Calories In: affected by digestion, absorption efficiency, food quality, gut microbiome, etc.
Calories Out: affected by basal metabolic rate (BMR), physical activity, NEAT (non-exercise activity thermogenesis), thermic effect of food, hormonal status, etc.
In summary:
CICO is a valid, thermodynamically sound principle. The complexity of human metabolism doesn't invalidate it — it just means real-world application requires nuance and context.