1Kg of human fat is around 8000kcals give or take.
50lbs is 22Kg. 176000kcal. It's 586x "extra slices of pizza", almost two years of overeating every day.
That's exactly what I said. 300 cals indefinitely. I obviously didn't mean you eat one slice of pizza and gain 50lbs.
It's easy to say "put down the pizza," but pizza is just an example.
300 calories is also 1/4 a cup of rice (50 cals), 1/3 service of chicken (100 cals) an egg (78 cals), a teaspoon of olive oil (40 cals), and a toast (75 cals).
There are lot of reasons its hard to cut weight. Measuring calorie intake to 300 calories is hard enough. But also, its easy to eat a bit more at each meal if you are hungry (and it adds up).
That is why weight loss is hard to achieve. If you are hungry, it's hard to--over an entire day--avoid eating 300 extra calories.