Hi
@Misja, I had some experience of doing this a couple of years ago and managed to go from overweight and 25% body fat to 12% body fat in 12 weeks, whilst increasing muscle mass.
The key was principally two things. Firstly a number of phases of training and diet were applied, and bear in mind that the numbers in here are all what were applied to me.
The first phase was a low carb diet, eating 2000 calories a day with a macro split of 45% Fat; 45% Protein; 10% carbs. This was done for four weeks whilst also undertaking a conditioning training programme, based on
German Body Composition training three times per week. Each training session was accompanied by BCAAs and a sugar free protein shake. You may or may not find them useful, but the BCAAs really reduced the muscle soreness I experienced. The important thing about this phase was to get the body burning fat and not lose muscle mass, which I found very successful.
Following this, for the next 8 weeks, we undertook fortnightly programmes doing low rep, heavy strength work for two weeks and then higher rep, lighter composition work for the next two. In this period, the diet added back complex carbs up to 20% of macro values but for the final two weeks reduced the calories to 1750 per day during a composition phase. Throughout the entire period, no alcohol was drunk.
I found it to be a very successful approach and I lost weight, gained insulin sensitivity and gained muscle. I could even see my six pack and no use of insulin as a growth factor was required.