4.1 Primary Energy Substrate

Primary Energy Substrate defines which substrate class carries long-term energy operation. It is the first control variable in Feline FBM energy regulation.

This is not calories alone and not an ingredient name. Substrate dominance determines downstream regulation.

If Exogenous Carbohydrate Load dominates entry, the system biases toward glucose scheduling. When exogenous carbohydrate is structurally low and the fatty acid pathway is supported, fatty acids fit long-term primary energy duty.

All backtrace returns to upstream food structure.

Higher load increases glucose scheduling pressure; fatty acids are harder to hold as primary substrate.

Fatty acids must complete digestion, absorption, transport, and utilization—not merely appear on a label.

Insulin Regulation State affects whether oxidation pathway can stay active.

When fat contribution is insufficient, protein is pushed into energy duty and raises Solute Load per Unit Energy.

Fatty acid supply changes intake volume, gastric residence, and solute handling per unit energy.

upstream food structure

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exogenous carbohydrate input level

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insulin regulation state

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fatty acid oxidation pathway open or suppressed

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primary energy substrate class established

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long-term observable outputs

Loose stool, urinary concentration, greasy coat, and coat changes are outputs that backtrace to substrate dominance—not proof of a single isolated nutrient.