People underestimate their food intake, and fatter people underestimate it more. Sometimes by astonishing amounts. I saw an episode of the BBC series Secret Eaters which featured a pair of sisters who both estimated their calorie intake - by food diaries - at 1200 calories/day. Actually, one of them was eating 3700 calories/day! This is pretty extreme, and I don't know how someone forgets about entire trips to a fast food place, buying candy bars in the grocery store, etc. More commonly obese people underestimate their calorie intake by 30-40% or so, but that's still plenty to cause a major weight problem. It's easy to eat fast food and snacks mindlessly, so this is part of the problem - the high-calorie snacks that are available everywhere.
People eating and managing to forget about it might be the main cause of the obesity problem.
So if you are someone who is overweight but believes they eat very little - how can you become conscious of what you eat and actually eat in a way that promotes weight loss?
If you did become aware of what you were actually eating and that you had been deceiving yourself - how did this happen?
You can't get away from salt. I thought I was low salt, but forgot to count my low carb ketchup. Even plain meat and fish is often surreptitiously puffed up with infused salt water.
I get an average of 370 mg sodium/day from my regular food. I use the USDA nutrients database to estimate such things. I'm getting some additional sodium from cultured fruits and veggies though.