How helpful are BCAA/HMB/Creatine supplements for preserving muscle mass if you are running a caloric deficit?
BCAAs (particularly L-Leucine supplemented with Vitamin B6) and HMB become more efficacious (i.e. useful, practical and important) as anti-catabolic agents when in a situation of calorie deficit, a conclusion that has been supported in a number of relatively solid scientific investigations. My own opinion during 40 years of experience as a trainer and gym owner, as well as a competitive bodybuilder, also supports this claim.
The further addition of creatine, especially in conjunction with a good resistance training scheme and not-too-much-cardiovascular and endurance training, will guard against the inevitable and real threat of catabolism and subsequent muscle loss that most people succumb to when dieting.