I came across this study some time ago and it has definitely stuck out in the articles I have read. Over a short time frame it would appear that keeping your protein high will fight off muscle loss (and for one group, increase muscle!) even when you’re restricting calories by %40!
What this has meant for my practice is that I will keep protein a little higher when prescribing a meal plan as well as not be too worried about under shooting the calories for the short term. What this also means is that you could probably restrict food even more between cheat meals and still have great fat loss without chewing through any muscle.
Lastly a little reminder to anyone reading the study and then thinking about dieting. The study was conducted for only 6 weeks, which is a very short amount of time when you talk fitness and exercise. Extreme restriction, like was done in this study, I would not suggest for the long term at all, and could cause metabolic damage if maintained for too long.