Food, cells and energy

Everything you do is powered by food, but the journey from a meal to usable energy is a small marvel of chemistry.

We eat to live, but the phrase hides a remarkable process: the conversion of a plate of food into the energy that powers every cell, every movement, every thought.

Where energy comes from

Essentially all the energy in food comes from three macronutrients, carbohydrates, fats, and proteins (with alcohol a minor fourth).¹ Each has distinct roles, but all can ultimately be broken down to release energy.

The cost of eating

Not all of that energy is free. Digesting, absorbing, and processing food itself requires energy, a phenomenon called the thermic effect of food, or diet-induced thermogenesis.¹ Eating, in other words, is not quite free; the body spends some energy to unlock the rest.

A meal is not energy. It is the raw material the body spends energy to unlock.

From macronutrient to fuel

Once broken down, glucose from carbohydrates, fatty acids from fats, and even amino acids from protein can be oxidised to produce ATP, the cell's universal energy currency, with muscle a major site of this fuel-burning.² Different macronutrients also affect fullness differently, with protein generally the most satiating.²

Why it matters

Understanding food as fuel, and the body as an efficient but not frictionless engine, grounds nutrition in something concrete. It is the chemistry beneath every choice about what, and how much, to eat.