Your brain makes up about 2 % of your body weight, yet it accounts for about 20 % of the energy your body uses at rest . It holds almost no fuel reserves of its own and depends on a constant supply of glucose – around 120 g a day. That figure is the reason official guidelines set the minimum carbohydrate intake for adults at 130 g per day .

Inside every neuron, mitochondria turn this fuel into ATP – the currency that pays for every thought, every signal and every bit of emotional regulation. Researchers increasingly study faulty mitochondrial energy production as one piece of the depression puzzle . A promising hypothesis, not a settled cause – but a useful lens: a brain that runs low on energy has less capacity to stay calm.

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