A kilo up or down in a day is not fat

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Stop 1/5

The scale reads a sum; fat is one term

EVIDENCEMECH 2

READ THE ORIGINAL

When you step on a scale, it does not read your fat. It reads the weight of everything on you at that moment added together: water, glycogen, what is still in your gut waiting to leave, lean tissue and fat. In the energy ledger, Hall 2008 splits a change in weight into just two parts, fat and lean tissue, with glycogen counted as part of lean tissue.

These terms change at very different speeds. Fat is the body's most concentrated energy store: pure fat holds about 39.5 megajoules (MJ) per kilogram, roughly 9400 kcal, while a one-kilogram change in lean tissue corresponds to only about 7.6 MJ, because lean tissue is mostly water. Water can move the number on the scale a lot, yet it carries zero energy.

So a kilogram up or down on the scale within a day is almost never fat that was gained or burned; the terms that change quickly are the ones that hold water.

Educational content, not medical advice. See a clinician about your own case.

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A kilo up or down in a day is not fat

Story

Read full story

Stop 1/5

The scale reads a sum; fat is one term

EVIDENCEMECH 2

READ THE ORIGINAL

When you step on a scale, it does not read your fat. It reads the weight of everything on you at that moment added together: water, glycogen, what is still in your gut waiting to leave, lean tissue and fat. In the energy ledger, Hall 2008 splits a change in weight into just two parts, fat and lean tissue, with glycogen counted as part of lean tissue.

These terms change at very different speeds. Fat is the body's most concentrated energy store: pure fat holds about 39.5 megajoules (MJ) per kilogram, roughly 9400 kcal, while a one-kilogram change in lean tissue corresponds to only about 7.6 MJ, because lean tissue is mostly water. Water can move the number on the scale a lot, yet it carries zero energy.

So a kilogram up or down on the scale within a day is almost never fat that was gained or burned; the terms that change quickly are the ones that hold water.

Educational content, not medical advice. See a clinician about your own case.