By the way, suddenly looking softer and smoother when you are normally hard and lean is due to excess cortisol and adrenaline (they go together) production.
Chronically elevated cortisol levels will:
a) Increase water retention by increasing aldosterone and vasopressin levels
b) make muscles appear smaller by reducing glycogen storage
Right off the bat this makes you look smaller, feel flatter and look less defined.
On top of that, if you overproduce adrenaline too often you will quickly desensitize the beta-adrenergic receptors. At the muscle level, the sensitivity of the beta-adrenergic receptors have a HUGE impact on muscle tone.
Muscle tone is nothing more than a partial state of muscle activation.
Activating the beta-adrenergic receptors at the muscle level will increase muscle activation, even at rest, increasing muscle tone.
So the more sensitive those receptors are, the more easily they are turned on by adrenaline, the higher is your muscle tone.
But if they become resistant, the opposite occur: your muscles have a very hard time being activated by adrenaline, which leads to a much lower muscle tone.
In fact, with athletes I use muscle tone changes to evaluate if the athlete is overtraining, can do more should do less, etc.
Adrenaline is produced in response to cortisol elevation. Chronically elevated cortisol will lead to chronically elevated adrenaline (that’s why you have a hard time sleeping when you are stressed). And that will lead to beta-adrenergic desensitization.
Now you have 1) water retention 2) flat muscles 3) low muscle tone… rapid changes in physique, for the worse.
Any type of training that leads to excessive cortisol/adrenaline levels over time can lead to those changes. Not just whole-body training. If load and volume is well planned, you should not be at a higher risk from whole-body training. BUT since whole-body normally relies on more multi-joint exercises and heavier weights, it means that other variables need to come down, volume and how hard you push your sets for example… or training density. If you keep a similar overall volume and intensiveness as in a bodybuilding workout, yeah, the whole-body approach will likely lead to more cortisol/adrenaline.