My natural limit for muscle mass

Having read that BMI isn't a great indicator of healthy weight range for those that doing weight training (those with lots of muscle can be 'obese' according to BMI, even though they have quite loss amounts of body fat!), I was reading up about the natural (ie. not taking steroids etc.) limits for how much muscle mass can be achieved. One measure is the so-called "fat free mass index" (FFMI) that calculates muscle mass for body builders and fitness enthusiasts, based on weight, body fat and height.

Plugging my current numbers into an online FFMI calculator, I get:
weight: 86 kg
body fat: 17%
height: 176 cm
FFMI = 23.1 (lean mass of 71.4 kg) and 'adjusted FFMI' of 23.3

For comparison, average male FFMI is around 18-19, 22 is 'excellent' and 23-25 'superior'.

The usual limit for FFMI is around 25, with a FFMI of 26-27 considered suspicious, as it is rare for this to be attainable naturally. An FFMI of 28-30 is highly unlikely without steroid use.

Anyhow, my goal is to continue weight reduction while on high protein ketogenic caloric restriction (to maintain as much lean mass as possible) until I reach my 'ideal' weight of around 76-80 kg and a body fat of around 10%-12%.

Out of interest, I plugged in my 'target' weight into the FFMI calculator to see what body fat percentage I would need to be if my FFMI remained unchanged:
target weight: 80 kg
target body fat: 10.5%
height: 176 cm
target FFMI = 23.1

This indicates that if I reduced my weight below 80 kg I'd either have to lose muscle mass, or else my body fat would be extremely low. For example, to be 78 kg and 23.1 FFMI, my body fat would need to be around 8.5%.

Conversely, if I keep my weight around 80kg (once I get there) while continuing to do weight training to add some more lean mass while reducing body fat further, the natural limit (FFMI 25) would mean being 'ripped' with a body fat percentage as low as 4%. I won't even get down to that sort of body fat percentage, so I think a realistic goal will be to aim for a weight of around 78-80 kg and a body fat percentage of between 8%-10%. We'll see how things progress during 2020...

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