Obesity is a complex, multifaceted disease that is widespread and growing in the developing world. People who are obese experience health-related quality-of-life impairments. Impairment in an obese individual's capacity to live as fully and actively as he or she desires may be as serious a consequence of obesity as its adverse effects on morbidity and mortality (1). Both physical and psychosocial functioning have been shown to be negatively affected by excess weight; greater impairments have been associated with greater degrees of obesity (2).

In 1947, the World Health Organization defined health as both the absence of disease and infirmity and the presence of physical, mental, and social well-being (3). Health-related quality of life refers to well-being in the physical, psychological, and social domains; well-being in each domain can be assessed by measuring an individual's objective functioning and subjective perceptions of health. Quality-of-life assessments can be used to measure and compare the effectiveness of different treatments and to evaluate the impact of a treatment on how patients feel and function in their everyday lives (4).

Until recently, there has been little standardization of quality-of-life measures among people who are obese; many researchers have simply developed their own set of nonvalidated questions. The field of quality-of-life research has grown, however, and standards for developing and validating quality-of-life instruments have been proposed (4-11). The SF-36 Health Survey (QualityMetric Inc, Lincoln, RI) has been used to study obesity because it is comprehensive, brief, psychometrically sound, and consistent with current guidelines for health-related quality-of-life instruments (4,11-15).

Our aim in this study was to compare the health-related quality of life of obese and normal-weight adults in Turkey. In addition, we sought to describe the conditions contributing to poor health-related quality of life among obese patients. We hypothesized that obesity negatively affects both physical and psychosocial functioning.

All individuals surveyed completed the questionnaire in full. Table 1 shows the mean age and BMI by sex for each participant group.

Table 2 shows the mean scores by sex for obese participants and normal-weight participants in each of the eight SF-36 domains. Differences in scores between obese women and normal-weight women were statistically significant in seven of eight domains; the sole exception was for vitality. Differences in scores between obese men and normal-weight men were statistically significant in six of eight domains; the two exceptions were for role-emotional and vitality.

We found that obese women were significantly more impaired than obese men in four of eight domains: role–emotional (P = .05), vitality (P = .03), bodily pain (P = .04), and general health perception (P = .001).

Among obese women, 45.0% (674/1498) experienced a reduced quality of life, compared with only 13.2% (33/250) of normal-weight women. Similarly, 41.3% (105/254) of obese men experienced a reduced quality of life, compared with 9.3% (14/150) of normal-weight men.

Table 3 shows how each participant group responded to each SF-36 question.

Obesity is a major public health problem associated with increased health risks (1,3,15-18). The results of our study showed that obesity was related to role-emotional limitations and physical problems. People with obesity uniformly perceive their general health as poorer than healthy-weight people perceive their health (3,18,19). Moreover, a continuum has been observed between mildly, moderately, and severely (morbidly) obese individuals and worsening perceived health status. Some studies found obesity to be associated with compromised quality of life and mental well-being (4,9,18,20,21). Obese people have also been shown to have poorer psychological profiles than other chronically ill people (16), and BMI levels have been found to be positively correlated with reports of self-harm and psychiatric illness (17,22). Investigators also found that higher waist-to-hip ratios are associated with lower socioeconomic status, work problems, unemployment, and increased sedentary behavior among men and women (4,23,24).

Fontaine et al administered the SF-36 questionnaire to 334 people seeking outpatient weight-loss treatment and found that they scored significantly worse than population norms in eight domains; they also found that a morbidly obese subgroup scored significantly worse in six of the eight scales (17). On the other hand, some studies found little difference between obese and nonobese groups in their scores on standard psychological tests (23-25).

Obesity is no doubt, however, associated with some loss of quality of life, particularly in physical well-being (22,26-29). In a population sample of 3443 men and women from the Netherlands, Seidell et al found that BMI was positively associated with the number of health complaints (20). Similarly, Richards et al compared the functional status of 345 sibling pairs, one classified as severely obese (BMI ≥35.0) and the other classified as normal weight (24). All SF-36 functional status and emotional well-being scores were significantly lower among the severely obese participants than among their normal-weight siblings. Furthermore, those who were severely obese perceived their general health to be poorer and more likely to get worse than did their normal-weight siblings (24).

Body-image dissatisfaction (19) and binge-eating disorder (18,30) are both more common among obese people than among normal-weight people (22). Although few obese patients have clinically significant problems with body image, binge-eating disorder is associated with high rates of psychopathology, particularly depression (25). Some obese people suffer from clinically significant psychopathology that requires treatment. Research is needed to examine factors that may increase the risk for psychopathology among the heterogeneous obese population. A recent study suggested that gender may modify the psychological risk of obesity. In a general population sample, excess weight among women was associated with an increased risk for major depression, suicidal thoughts, and suicide attempts (11,28), whereas excess weight among men was associated with a decreased risk for depression and suicidal behavior (28). Similarly, Sullivan et al found that the psychosocial consequences of obesity were greater among women with a BMI greater than 34.0 than among men with a BMI greater than 38.0 (29).

Mathias et al reported that obese patients scored worse than normal-weight individuals on ratings of overweight distress, physical appearance, and health-state preferences (31). Doll et al found a strong inverse relationship between BMI and quality of life (32). In our study, we found obesity to be associated with both poorer quality of life and decreased mental well-being, compared with normal weight. For example, we found that 25.9% of obese women and 16.2% of obese men reported difficulty bathing or dressing themselves; only 7.8% of normal-weight women and no normal-weight men found difficulty with this task. This finding shows that obesity affects physical well-being and the ability to perform daily activities.

Evidence of a negative correlation between obesity and psychological quality of life is equivocal, and it is much weaker than evidence of a negative correlation between obesity and physical quality of life. Earlier studies found few or no differences between obese and normal-weight people in psychological functioning (1,2). Similarly, recent population-based studies demonstrated marked differences between obese and nonobese people in their physical quality of life but few differences between them in their psychological or social quality of life. Nevertheless, there is some good evidence that obesity does negatively affect psychological quality of life (4,32,33).

Studies of self-reported health status show that women are more likely than men to report impaired health (28,30,31,33,34). Similarly, women are more likely than men to report impaired body image or body satisfaction, and obese women are more likely than obese men to report impaired health-related quality of life (35). In our study, we found that obese women were significantly more impaired than obese men in four of the eight quality-of-life domains. The results of our study add to the substantial body of evidence that obesity is associated with poor levels of health status, particularly with poor levels of physical and social well-being.