After few years of training and being lead by a personal trainer and a dietician I'd add one thing: It's crucial to have a high BMR - basal metabolic rate, whe

After few years of training and being lead by a personal trainer and a dietician I'd add one thing: It's crucial to have a high BMR - basal metabolic rate, when going into a deficit. Any deficit will cause body to lower the BMR and, if it's going into < 1800kcal/day (for man) it will generally result in problems. Body is very adaptable and will just shut down any energy hungry "facilities": lower body temperature ("I'm cold all the time", "I always have cold last two fingers"), increase sleep duration, decrease immune responses ("Why I get flu all the time in season, while others don't?") and so on. It will loose fat, but if BMR is low, then it's also in the shock mode, where it will want to get that back as fast as possible, with some extra. That's how the yoyo effect work on physiological level. So, start cutting on BMR of 2500-3000. It won't drop into dangerous levels and will be lower impact on the body