I generally start people on 1g of lean protein (from lean meats) and 1g of carbohydrate (from vegetables, and a select few starches -potatoes, rice) per pound of lean body mass, with dietary fat as by-product of your protein sources (assuming you are eating things like chicken, fish, and lean beef). No added fats. The science and reasoning behind this is complex (amino’s support a positive nitrogen balance and protein synthesis, carbohydrates fuel the anaerobic energy production pathway, the ratios control blood sugar and insulin/glucagon axis etc.), but the practical application is simple. Eating starchy carbohydrates is blasphemous to low carb proponents, but again, we are talking about a physique goal beyond just “normal”. And we are talking about an anaerobic athlete vs. a sedentary slug.
2. Your body fat percentage is a ratio of fat:lean muscle mass. There are 2 ways to improve this: dropping body fat AND gaining muscle. Too many people focus on the first and not the second. And especially if you are a naturally “leaner” type, you need to focus just as much on building muscle as you do dropping fat. I would do a 4-day traditional bodybuilding-style split, 3 sets of 10, higher volume, etc, which has been researched and proven to be the best plan for muscular hypertrophy.
Cardio sucks for fat loss and circuit training is a myth. Its not about how many calories you burn while exercising, its about how many calories you burn the other 23 hours of the day in the recovery process, and the metabolic and hormonal effects of your training program. Traditional strength training/bodybuilding training is far superior in these aspects. Your training should not be geared towards burning calories, it should always be about building muscle (even if you just want to burn fat, because lean muscle contributes to a higher resting metabolic rate). Let your body burn fat in the recovery process, combine that with a targeted nutrition plan, and you’re on the road to Rippedville.