If your resolutions for the New Year are typical, they include a pledge to lose weight. But if you are like most Americans, any success you have shedding pounds will be short-lived, and you'll end the year weighing more than you do right now.

So why are Americans obsessed with weight loss? Many people say they want to lose weight to improve their health, but this may not actually be their primary motivation. In one instance, more than three-fourths of 231 dieters surveyed said that they would take a pill that would guarantee they would achieve or maintain their desired weight even if it would lower their life expectancy. On average, they were willing to give up 5.7 years. Moreover, 91 percent said that they would not take a pill that would lengthen their life by five years if it guaranteed that they would also remain overweight.

This was a small sample, but it is consistent with other research. A book published just last year showed that the desire to fit in or be "normal" - rather than improving health - is the primary motivation for many who undergo weight-loss surgery.

These findings are not surprising when you consider weight-loss attempts for what they really are: efforts to protect against weight-based discrimination. The fact is, fear and loathing of fat are real, and attitudes about fat may be more dangerous to public health than obesity itself.

Yale researchers have shown that weight discrimination in the United States has increased dramatically in the last decade and is now comparable in prevalence to rates of reported racial discrimination, especially among women. Multiple studies have documented weight bias in employment, health care, education and public spaces - unequal treatment based on stereotyping fat people as lazy, unmotivated, sloppy and lacking in self-discipline and competence.

When I was doing research for a book on the social understanding of fat, several heavy women told me they were often reproached for eating in public. Some tearfully shared stories of having had people actually throw food at them. Heavy women are routinely ridiculed in advertisements, television and film. Even children express negative attitudes about their heavier peers, a tendency that has gotten worse in the past 40 years.

Of course, there are genuine health risks associated with higher body mass. The clearest case is that of Type 2 diabetes. Yet as many medical researchers have pointed out, it's not clear whether obesity per se causes diabetes, whether diabetes causes obesity or whether both conditions are caused by a third factor, such as poor nutrition, stress or genetic factors.

The link between weight and health is complicated. In some cases, higher body mass seems to protect against mortality. There is growing evidence documenting an "obesity paradox," in which elevated body mass is associated with lower mortality among people with heart disease and among those with Type 2 diabetes. A recent report in the Journal of the American Medical Association concluded, after analyzing almost 100 studies, that people with body mass indexes in the overweight category were at less risk of dying in a given year. In fact, they found that even those in the moderately obese category - in which the greatest number of Americans classified as obese fall - were at no greater risk of dying than those in the normal weight category.

We have much to learn about what these observations mean. But it is clear that anti-fat bias in and of itself takes a toll on public health in many ways. Fear of ridicule leads many heavier women to avoid exercising in public or even to avoid leaving their homes, depriving themselves of social interaction. Because many heavier women experience the doctor's office as a hostile environment, they are less likely to get Pap smears, which leads to higher rates of cervical cancer. And fear of becoming fat can lead women of all sizes to develop eating disorders and body image problems dangerous to their health.

What should be done about weight-based discrimination?

The answer is to call for increasing tolerance and appreciation of diverse body types. This year, before embarking on yet another diet, ask yourself why you want to lose weight. If it is to improve your health, perhaps you should focus on behaviors that are more directly linked to health: Pledge, for example, to get more sleep, eat more fruits and vegetables, get regular physical activity, or spend more time with friends.

But if you are trying to change your body to shield against discrimination and stigma, consider making a different kind of New Year's resolution: to stand up to intolerance and bigotry in all its various forms, whether racism, sexism or fatphobia.

Abigail Saguy is an associate professor and vice chair of sociology at UCLA and the author of "What's Wrong With Fat?" She wrote this for the Los Angeles Times.