Re caloric intake. It goes without saying that you must run a net caloric deficit in order to lose weight. In order to do this, you have to know how many calories you’re taking in, and how many calories you’re expending.
On the intake front, this means you HAVE to measure/weigh your food (with the exception of cruciferous/leafy veggies, which are always ‘free’). ‘Guesstimating’ won’t cut it–believe me, I’ve tried. (It’s amazing what being hungry can do to one’s perception of what 10 oz of food looks like.) I got a good electronic food scale from Amazon for $25 a few years ago. (Not sure if TN will allow me to link it.)
On the output front, I’m afraid guesstimating is the only practical approach. The rule-of-thumb re caloric expenditure in an adult male with a non-manual-labor job is ‘BW x 15’ on lifting days, and ‘BW x 12’ on rest days. Working off of a BW of 300# for you, this comes to 4500 cals on lifting days vs 3600 on rest days. These are the numbers I suggest you use when setting your caloric intake goals.
It takes a deficit of 3500 cals to lose a pound, so if you wanted to lose a pound/week, you need your weekly deficit to hit 3500. How you get there is up to you. You could run a constant deficit of 500 cal/d, but I personally find that less appealing than having some days higher and some lower; that is, I would rather eat at maintenance one day and a 1000 cal deficit the next than eat at a 500 cal deficit on both days. Further, since I’m going to eschew all carbs on nonlifting days, I like to run a substantial caloric deficit on those days; this allows me to ‘save’ more carbs/calories for lifting days.
I think you mentioned planning to lift 5d/week. Based on that, you could reach a 3500 cal/week deficit thusly:
–2 off days @2600 cals (deficit = 1000 cal/d; total deficit = 2000 cals)
–2 lift days @4500 (no deficit)
–3 lift days @4000 (deficit = 500 cals/d; total deficit 1500 cals)
As for macros, the primary means of moving the cals up and down is via manipulating carb intake (and to a lesser extent, protein):
–Off days: 400 g protein (1600 cals), 100 g fat (~1000 cals), ~20 incidental carbs (~100 cals)
–No deficit days (high-carbs!): 250 g protein (1000 cals), 600 g carbs (2400 cals), ~100 g fat (~1000 cals)
–Deficit lift days: 300 g protein (1200 cals), 300 g carbs (1200 cals), ~160 g fat (~1600 cals)
I’m not gonna lie–the 1000 cal deficits on the off days will SUCK. (As mentioned above, coffee can be a diet-saver on such days). But you get through them by knowing a high-carb day is just around the corner (you might consider scheduling the high-carb days to follow the no-carb days for this reason).
Anyway, these are the basic ideas underlying how I managed to drop weight. Hope it helps.