According to research presented at a recent conference of the American Heart Association (AHA), many obese and overweight women and children rate themselves as being lighter than they actually are. Normal weight people are much less likely to do this. Since being overweight or obese is linked to a laundry list of health complications, this shift in perception of body image is not a healthy change.

Children who were overweight or obese underestimated their body weight 86% of the time, vs. only 15% of the time for normal weight children. Just over half of the mothers who had overweight or obese children actually thought their children were overweight or obese.

In the new study, researchers followed a sample of urban, largely Hispanic, mothers and their children. They measured the participants’ body weight and height, and from these numbers, each person’s body mass index (BMI) was calculated. The participants were also asked to estimate their own body weight: looking at silhouettes of varying sizes, each participant was asked to choose the one that best represented his or her own body.

The government’s current convention is that BMIs of 18.5-24.9 are considered normal; overweight is defined by the 25-29.9 range, and anything over 30 is considered obese.

The researchers found that about two-thirds of the mothers and 39% of the children were either obese or overweight. A whopping 82% of the mothers who were obese underestimated their own body weights, and 43% of the mothers who were overweight underestimated theirs. Mothers who were in the normal weight range only underestimated their body weight 13% of the time.

A similar trend was found in the kids. Children who were overweight or obese underestimated their body weight 86% of the time, vs. only 15% of the time for normal weight children.

Just over half of the mothers who had overweight or obese children actually thought their children were overweight or obese. Similarly, children tended to pick larger silhouettes than their mothers did to represent an "ideal" or "healthy" body weight for a woman.

Lead author on the study, Nicole E. Dumas, said in the AHA news release that her team’s "findings imply that not only is obesity prevalent in urban America, but that those most affected by it are either unaware or underestimate their true weight." She added that the American standard seems to have changed: "obesity has become an acceptable norm in some families. Strategies to overcome the obesity epidemic will need to address this barrier to weight loss."

While numerous public health campaigns have tried to promote weight loss and healthy living, obesity has become more common for Americans than being of normal weight. Some research has shown that weight loss campaigns may be ineffective since they can often offend rather than encourage their target audience. More research will be needed to figure out just what Americans need to become healthier, and to "reset" the current norm to a healthier body image.

Dumas is a resident at the Columbia University Medical College. The research was presented at this year’s Nutrition, Physical Activity and Metabolism/Cardiovascular Disease Epidemiology and Prevention 2011 Scientific Sessions of the American Heart Association.