A 6 pack to a love handle (say, 10% body fat changing to 20%) is noticeable, but fat to very fat (say 30% body fat to 40%) gives less visual clues to work with.
For further insight, lets go to Mr Large Person and Mr Serious,
Part of the problem is that in a society getting larger and larger, the norm is overweight, which means many will not see this as an issue. Few over weight people saw themselves as overweight (58% said normal weight), even fewer obese people (10%) knew they were obese. This is compared to 80% normal weight people who knew they were normal weight. This lack of knowledge will likely reduce motivation to change, and mean simple, but important, decisions about a lifestyle may not occur.
So what do you take from this? For yourself, BMI, calliper measurements, tape measurements, and body fat analysers are not perfect, but you don’t really need to be accurate to 0.1%, or half a pound (BMI is especially bad if you are a trained individual or older). They will give you a vague idea of where you are and where you need to be. For the people you know, be honest, because they may be unable to be honest with themselves.