Is a large caloric deficit necessary or does the Zone ratio (40-30-30) itself promote enough fat loss that one should be only concerned with getting enough calories to ensure optimal effort and recovery? Also, I've seen some strange formulas on caloric needs. In your personal opinion, how do you figure proper caloric reccomendations based on on protein requirements?
If you hit the 40-30-30 ratio and follow the sub-500 calories per meal intake recommendation (discussed in various Zone-related books) you will probably be eating fewer calories than you are now. It's tough to follow the weight-loss rules associated with the Zone and eat over about 2500 calories per day. However, if you bump fat intake as the way to increase calories you can top 3000 easily. So, yes, managing insulin is the key to tuning for fat metabolism, and caloric restriction will naturally happen by following the sub-500 calories per meal rule. However, if you want to get radical to strip fat off quickly then follow the Zone ratios and further restrict calories. This cannot be maintained for long, and your recovery speed will tell you when to start eating more. Based on our discussion of your situation I suspect that you can follow the ratio, and follow the 500 calorie rule, eat 5-6x per day and simply increase fat to keep the hunger at bay as needed. If you don't feel hungry about four hours after the meal the ratio was probably right. If you get hungry sooner there were likely too many carbs in the previous meal.
To determine the quantity of protein needed depends on whose theory
you want to follow:
Sears said something like if 5x1 hour of training per week then 1.8g/kg and if 5x2 hours of training per week then 2g/kg but I don't recall any changes recommended based on intensity or type of training so the prescription is vague at best.
In his book titled Advanced Sports Nutrition Dan Benardot suggests 1.2 - 1.7g/kg. The figure comes from a paper by Martin J. Gibala, Ph.D., which you can find on the web. Benardot states that most athletes consume more than they require, which I agree with since most protein recommendations have been polluted by the influence of bodybuilding and its emphasis on mass for the sake of mass without regard for health or athletic/sport performance.
The International Olympic Committee Consensus on Sports Nutrition recommends 1.2-1.4g/kg for endurance athletes and 1.2-1.7g/kg for strength/speed athletes. Some studies show that training increases the efficiency of protein utilization so taking more to account for exercise may not be necessary. However, weightlifters fed 2.1g/kg gained more mass on the same training program as lifters eating 1.2g/kg so the objective will also determine the ratio. Tracking back to Sears' recommendation, which appears high, it may be so to account for the fact that the Zone is a calorie-restricted diet and there is some science and anecdotal support for increasing protein intake when calories are reduced.
I suggest you start somewhere in the 1.5g/kg range, which is plenty to maintain muscle and recovery. Then start with an equal number of calories from fat as from protein (if 1.5g/kg protein then roughly .7g/kg of fat) and adjust the fat calories up from there as needed to ensure you get enough calories and to control the hunger issue. Carb recommendations vary wildly depending on how evil one thinks they are. Personally, I can't get extreme about it though I have done so in the past. One could start with the 40% recommended by Sears and adjust as needed throughout the day according to duration and intensity of one's training. If engaged in endurance exercise adjust carbs upward in the post-exercise recovery window to replenish muscle glycogen then eat a normal Zone or Paleo type diet the rest of the day. It is dangerous to fall for the idea of the fixed ratio: if activity were fixed then maybe fixed ratio and intake would be viable, otherwise I don't think so, at all.