If you eat enough protein you don't lose the muscle (just the strength which can come back later). But building muscle needs calories and if you start from an initial high bodyfat level, it will go up not down while gaining strength/mass. Now you end up in a worse situation even if you do gain some muscle your overall bf% is higher and you're relatively weaker. No win.
The better formula is diet down to 10% (say). Maintain it a while (hard for me). Then mass gain patiently up to goal weight (80-85kg for me) while maintaining or not straying far from goal bodyfat (10%). Not sure I can get up to lean 85 or 90kg without drugs tho but I'm sure gna try get to a lean 80kg without them.
Most ppl don't understand that someone who is 10% at 70kg and someone else who is 10% at 90kg have only 2kg of fat separating them. Diff between 10% at 70 and 100, yup only 3kg If you can afford to lose 5kg of fat, you're too heavy. I can afford to lose more than 5kg
. For what it's worth to justify carrying an extra 5kg bodyfat, I would need to weigh 120kg at the same bf. That's basically what you guys are suggesting to be ok with having the same amount of bodyfat as someone who weighs 120kg. And yes I test my bodyfat ALL the time, i habitually pinch my skinfolds around my waist all the time and can tell when im getting fatter or leaner. That's the best bodyfat test I know of.