I've recently dropped from 85kg 16.5% body fat to 79kg and 14.5% body fat.

Does that mean that I had:

14kg of body fat (16.5% of 85)

And now I have:

11.5kg of body fat (14.5% of 79)

Meaning that I've lost 2.5kg body fat?

If so does that mean I've lost 3.5kg of muscle?

Is that a bad ratio of kg to % loss if I was hoping to retain muscle just gain more definition?

Would it have been possible to drop 6kg and 5-6kg of it been body fat?

2 Answers 2


Very few of the common methods of assessing body composition are so accurate. That is, they can be under ideal conditions—a highly skilled tester, excellent equipment, euhydrated state, and/or typical body electrolyte levels—but very rarely do these factors come together. So unless you are having your body composition assessed professionally, you should assume a high degree of uncertainty in the measurements.

However, if were are to assume, hypothetically, that the measurement is perfectly accurate, it does indeed mean that you will have lost 2.5 kilograms of body fat, in accordance with your calculation. But it would be highly unusual (read: entirely improbable, if not impossible) that muscle would account for the remaining mass.

Significant fat loss is always associated with some muscle loss, but never in such proportions. The bulk of the difference is almost always fluid loss, which is the consequence of muscle and liver glycogen depletion. Even under normal conditions, our mass can fluctuate by 1-2 kilograms. Under a restrictive diet and/or intensive exercise regime, the difference can be considerably greater.

Thus, what you are witnessing is most likely a combination of measurement uncertainty and glycogen-associated fluid loss.

I hope that helps.


Would it have been possible to drop 6kg and 5-6kg of it been body fat?

No, with body fat you always lose some water and muscles, but it doesn't have to be muscles when you lose it slowly and eat enough protein.

I don't know how fast you lose it, your caloric deficit and the ratio of macronutrients in your diet, so you could lose 2.5 Kg of body fat and 3.5 Kg of water at best with great calculated diet or 2.5 Kg of body fat + muscles and water.

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