I don't follow any specific diet. When I want to lose weight I follow the simple manifesto rule Michael Pollan advanced in his book, In Defense of Food. "Eat food. Not too much. Mostly plants." Then I count calories with an iPhone app that I have with me most all the time called, Lose It! It is pretty easy to track because you can search maybe a half million foods, scan barcodes with the app of the foods you buy or create custom foods you eat. Once you have a weeks worth of food entered by various ways you pretty much have what you habitually eat and entering foods is very quick from your own personal foods library. Entering as you go is a constant reminder.
To track calories you set up a personal profile of yourself (current weight, height, age, activity level), how much weight you want to lose and how fast. That will tell you how many calories you can eat in a day. By tracking you start to see how meaningful Michael Pollan's manifesto is. Processed foods and empty calories add up fast. You start seeing that eating food and mostly plants means real food not processed food. You quickly learn how to get the most bang for your buck so to speak. Then if you are doing that you end up eating more sensible. You can eat sensibly or you can track and just simply stop eating for the day when you reach your maximum. You quickly learn if you eat at a restaurant you pretty much blow your budget no matter what and most likely will not see a weight loss but a weight gain the next day because restaurants use way too much salt to where you retain water (and weight of course). It is temporary but frustrating.
Now for the serious matter - Pizza. I broke down my recipe for a simple personal 11" Margherita pizza as follows:
Flour, 2/3rds cup rounded off = 293 calories
Sugar, 1 teaspoon = 17 Calories
Salt, 1 teaspoon = 0 calories
Yeast, 1 teaspoon = 13 calories
Extra virgin olive oil, 1 tablespoon = 120 calories
Mozzarella cheese, 4 oz. = 361 calories
Red tomato sauce, 1/4 cup = 30 calories
Garlic, Oregano, Basil = 5 calories
Total Pizza = 839 calories. That is almost half my daily calorie allowance.
From there you can add other condiments like pepperoni at 10 calories per piece, more cheese (adds up fast), black olives, Italian sausage, etc. A loaded pie of that size is going to hit 1200 calories plus or minus.
Bottle of beer? An American Lager is about 153 calories. A light beer about 103. But if you drink high alcohol content craft beers they will surprise you. a bottle of IPA could be over 180 calories and a pint glass well over 200.
Here is the real kicker and why people say they hit a wall in weight loss. The more you weigh the more you can eat in calories and still lose say a pound a week. But as you lose weight you have to eat less to lose that pound. It is the same with exercise. The more you weigh the more calories you burn. We went snowshoeing today. Since I weigh 50 pounds more than my wife I burned 600 calories on our trip and my wife only got credit for a little less than 400 calories burned.
My one last rule. It doesn't do you any good to lie to yourself. For instance you can say a beer is a beer and is 150 calories and then go and drink IPAs but it only affects you in the bottom line. Also, if you have to round off calories or guess the food value, just round up.