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5 MINUTE GUIDE: DIETS
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The Calorie
Energy is measured in Calories (officially spelt with a capital C), sometimes called kilocalories. The Calorie was first defined in the early 1800s as the energy needed to heat 1kg water by exactly 1°C.Our food provides the energy we need to live and, in the 1880s, scientist Wilbur Atwater used a 'bomb calorimeter', which calculates a change in heat in a closed container, to measure the energy contained in different foods. The theory was, if you ate fewer calories than your body burned up, you would lose weight. And so, our obsession with calorie counting was born.
This theory does work, but it's not as simple as it sounds. The trouble is, if you cut your calorie intake too drastically, your metabolism slows down so you burn up less energy. This is a mechanism to help us survive starvation.
Scientists have known for a long time that restricting calorie intake prolongs life in many creatures. The mechanism for this is not really understood but the latest research seems to show that the stress caused to cells by having too few calories triggers certain genes to rev up and help protect the cells from diseases of ageing. Unfortunately this effect seems to be more dramatic in mice than in humans.
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