The biotin is for hair and nail health, as some people have hair loss when they are in calorie deficit.
I have seen a lot of people say that disturbed sleeping patterns are a side effect of MJ, and magnesium is supposed to help the production of hormones that regulate sleep, in fact it helps with the production of all hormones in the body. It can also help with bone and teeth health and the maintenance of muscle mass.
Its found in a range of foods like green leafy vegetables but also nuts and cheese (which are things I generally don’t eat while watching my calorie intake)
I have seen lots a positive posts about using magnesium as a supplement generally but particularly when taking MJ.
I have also bought one of those led face masks to try and reduce wrinkles on my face as I hope to loose some of the fats from my face, and use moisturiser on my thighs and upper arms at night.
I too worry about excess skin, but on the balance of loosing weight and having a healthy BMI it’s something that hasn’t put me off taking MJ, it often happens to a certain degree of loosing weight using any means or after pregnancy. My tummy already has an apron from two C- Sections which is easy to hide in a swimming costume if it has some added secret support.
I hope that’s helpful, and good luck on your weight loss