A few years ago I saw a survey in USA Today which indicated Americans are too optimistic when it comes to their health. The survey stated that 30% of overweight Americans actually think they are in the healthy weight range. Here is the link to the story. I have to admit that in the past when I was in the overweight category I felt normal and healthy, so I can see how this could happen to other people.
One reason why people may have a skewed perception of their body weight is probably ignorance. Most of us don't have height and weight charts memorized and are not familiar with the healthy ranges. I think these can be beneficial for the masses, but using BMI tables doesn't work for everyone. A body builder with 6% body fat, could be categorized as being obese since these charts only look at weight and height and don't factor in body composition. For that reason, I try not to put too much stock in BMI numbers when I'm working with my clients.
Weight gain creeps up on us as individuals, but it has also done so to us as a society. Some time ago I was trying to explain what hippies were to my kids, so I Googled some images to show them. I was surprised when I couldn't find any overweight people in all the group pictures from the 60's that I looked up. These days we eat larger portions and more calories than we used to. Our activity level has also decreased due to technological advances and our sedentary lifestyles only compound the problem.
Another factor contributing to the confusion is the fact that many clothing manufacturers have fudged a little when it comes to clothing sizes. Their sizes today are more generous and often have more elastic or stretch to the material. Maybe they'd rather have someone happy thinking they still fit into size 34 waist pants rather than make the consumer uncomfortable. I guess 34 is the new 36.
If you suspect you are one of those people who might be in denial, then it may be helpful to do regular fitness assessments to keep things in check. Weighing yourself and taking your measurements on a regular basis is one good way to catch the creeping weight before it sneaks up on you.