As someone who just lost 35 pounds through clean dieting:

All calorie/portion numbers on packaged food are off by 10-20%. I set MyFitnessTracker to 1.5k calories (deficit for my build) and for weeks nothing would budge - even with strict portion control and weighing everything, plus 800 extra cals spent through exercise.

Once I went to "1250" calories, I started losing weight. Went from to 205 to 175 pounds.

With packaged food I mean anything like cream cheese, various sides, etc. - not pre-built meals (I assume those would be off by 50%).

What weighing your food really does, is reveal how shockingly little you actually should be eating. I switched to small plates for all meals, as using the normal large ones was pointless and slightly de-motivating.

But yeah, it's just calories. No matter what you eat.