@CemokW@dwightnyamouth@Devsthetix additional contractile proteins (i.e. muscle fibres) will form via mechanical tension from training. Nothing in this process is dependent on calories.
Large calorie deficits may be considered as a stressor (equivalent to poor sleep) but thats a different conversation
@vertile1913@dwightnyamouth@Devsthetix yes if your body classes the deficit as a stressor you will atrophy quicker (will mainly happen with an aggressive deficit). but the only difference between a slight calorie deficit and a surplus will be you might feel a bit more tired during sessions.
You still build muscle