Ok, you have been fed some bullshit. Anyone who just gives you a “eat X calories” advice without knowing your age, height, gender, etc… is full of shit. Makes me no end of mad when you see “Contains 25% of your daily…” on food packaging. Because a 19yo male rugby playing bricklayer and a 46yo female accountant have vastly different requirements.
At the core of it, its CICO (Calories in, Calories out)
www.calculator.net/macro-calculator.html Tap your details into that, select a REASONABLE weight loss goal a week, underestimate your exercise, and select the high protein option since you are weight training and want to avoid muscle loss.
A few eggs on a couple of pieces of wholemeal or multigrain toast, pot of greek yoghurt and a coffee is a perfectly good breakfast and Protein shakes are a great way to get protein in and keep calories reasonable, my lunch at work is 2 scoops of Casein protein and a protein bar. I eat boring and super low cal during the day because I train in the afternoon and want to enjoy my dinner.
When it comes to adding back in workout calories… both sides are right. “Diet fatigue” is a real thing, and if you want to keep your calorie defecit around a certain number to avoid getting burnt out then yes, you add them back in. Personally I calculated my macros and calories to “mild” weight loss and estimated my exercise as “none” so my training was where I found the larger part of my deficit.
I could write a very short book on this stuff so if tou have any questions feel free to PM me.