Abstract
Introduction
Despite the association of central obesity with adverse outcomes, most patients with CVD are unable to successfully lose weight. We undertook this analysis to evaluate the effect of motivational factors, and clinical factors, including physician diagnosis of overweight, on weight loss in patients with CVD and central obesity in the United States.
Methods and Results
We used data from the National Health and Nutrition Examination Survey (NHANES) 1999 –2004. Waist circumference ≥ 102 cm in men and ≥ 88 cm in women were used to classify central obesity. We examined demographic, motivational and clinical determinants of attempted and successful weight loss using multivariable logistic regression. Successful weight loss was defined as ≥5% weight loss in the preceding year. There were 907 respondents with CVD and central obesity of which 78% were aware of their overweight status and 80% were desirous to weigh less. Despite this awareness and desire, only 49% of centrally obese adults had attempted weight loss in the last year. Only 62% (n=584) reported that they had been informed that they were overweight by a physician. On multivariable analysis, physician diagnosis of overweight was a significant predictor of weight loss attempts (OR 2.42, 95% CI 1.44-4.09, p= 0.006) and successful weight loss (OR 2.70, 95% CI 1.40-5.19, p=0.001).
Conclusion
In a nationally representative sample of adults with CVD and central obesity, physician diagnosis of overweight status emerged as a significant predictor of attempted and successful weight loss.
INTRODUCTION
The prevalence of central obesity in the United States has risen markedly in the last few decades. (1) Central obesity has been linked to increased risk of coronary heart disease (CHD) and stroke, and it also been linked to poor outcomes in patients with different types of cardiovascular disease.(2, 3) The American Heart Association and other professional societies recommend assessment of obesity using indices such as body mass index (BMI), waist circumference and waist to hip ratio. They also recommend weight reduction in all patients with coronary artery disease and BMI ≥ 25 kg/m2.(4, 5)
The relationship between BMI and CHD events and mortality in patients with established cardiovascular disease is complex, with a U-shaped relationship being observed in most cohorts. (6) Several studies have actually shown that abdominal obesity is more strongly associated with CHD risk factors and CHD events, than weight-related measurements such as BMI in people with (7-9) and without CHD (10, 11). In light of existing findings, abdominal adiposity (or central obesity) may be a more important prognostic marker in patients with cardiovascular disease than BMI itself.
Unfortunately obesity in patients in cardiovascular disease is not commonly recognized, diagnosed or identified as a treatment goal, thus limiting the opportunity to establish effective lifestyle modifications and aim at weight reduction.(12) While the benefits of physician counseling for lifestyle change have been well documented (13), whether recognition overweight status by physicians in patients with cardiovascular disease is associated with actual weight loss is not clearly established. Published literature on predictors of weight loss in obese patients with cardiovascular disease is also scant.(14) Moreover, little is known about the role of motivational factors involved in weight loss (like awareness of overweight and desire to weigh less) in patients with cardiovascular disease. (15, 16)
The goal of this analysis was to investigate patterns of weight loss in community-based adults with cardiovascular disease and central obesity. To accomplish this we investigated the effect of sociodemographic, motivational and clinical factors, including physician diagnosis of overweight, on weight loss in respondents in National Health and Nutritional Examination Survey (NHANES).
METHODS
Study Population
NHANES 1999-2004 included nationally representative cross sectional samples of civilian noninstitutionalized adults living in the United States. The procedures involved have been described and published elsewhere and are also available online.(17) Each of these surveys included a stratified multistage probability sample based on selection of counties, blocks, households, and persons within households.
In this analysis adults with history of cardiovascular disease and central obesity were included. We considered participants to have cardiovascular disease if they responded ‘yes’ to whether they had been told by a physician that they had had coronary heart disease, angina pectoris/angina, myocardial infarction, stroke or congestive heart failure. We defined central obesity in accordance with NCEP ATP III guidelines based on waist circumference ≥102cm for men and ≥88 cm for women.(18) Respondents may or may not have been obese by BMI criteria (BMI ≥ 30 kg/m2 ) to be included in this study. Standing height and weight were measured by trained observers in a mobile examination center using standardized techniques and equipment.
Weight loss-related motivational and behavioral variables
Participants were administered interviewer-assisted questionnaire to ascertain their weight-related history and behaviors. In this study data from this questionnaire were used to create five binomial weight loss-related motivational and behavioral variables: awareness of one’s overweight status, desire to weigh less, attempted weight loss in the past year, attempts at maintaining present weight and successful weight loss.
Respondents were asked if they considered themselves to be overweight, at the right weight or underweight. Respondents who considered themselves overweight may actually have been either overweight or obese based on measured BMI, but the term ‘overweight’ has been used for the purposes of this study. We classified centrally obese participants as being aware of their overweight status if considered themselves to be overweight. Participants were also asked if they would like to weigh less, stay the same, or weigh more. We identified centrally obese participants who responded that they wanted to weigh less as desirous of weigh less. Others were classified as not desiring weight loss. Participants who had attempted weight loss in the preceding year or who had experienced intentional weight loss in the preceding year were classified as having attempted weight loss. Participants who had tried to maintain their weight in the prior year were classified as having attempted to maintain their present weight.
Respondents were also asked to report their current weight and height, and their weight one year ago. Percent weight change was determined by taking the difference between the current and one year previous reported weight and dividing that by participant’s weight one year previous. We considered participants who had lost ≥5% of their reported weight in the last year and had intended or attempted weight loss as having experienced successful weight loss. (19-22) Participants who lost ≥5% of their body weight, but had not intended/attempted weight loss were excluded from analysis that examined covariates of successful weight loss. Participants who had lost < 5% of weight or had gained weight in the last year were considered unsuccessful in weight loss. Participants were also asked at what age and weight they had been heaviest. This information was used to classify participants as those who had experienced successful weight loss in the past (≥5% of their maximum body weight prior to the last year) and those who had maintained this weight till the beginning of prior year. We also subtracted the age when respondents had been heaviest from their age one year previous to calculate the time interval that had elapsed since they had been at their maximum weight.
Respondents were also evaluated for whether they had been informed of their overweight status by physicians by asking them, “Has a doctor or other health professional ever told you that you were overweight?”
Sociodemographic and Clinical Variables
Sociodemographic information is routinely collected as a part of NHANES. We used information about participants’ age, gender, ethnicity, household poverty income ratio and education level (more than high school or less). The poverty income ratio is the ratio of family income to the family’s appropriate poverty threshold. We also used information from questions on smoking to classify participants as current, former (no cigarettes in last month) and never smokers (less than 100 lifetime cigarettes).
Respondents who reported that they had been informed by a health care provider that they had high blood pressure, or had systolic blood pressure ≥ 140 mm Hg or diastolic blood pressure ≥ 90 mm Hg or were taking antihypertensive medications were considered as hypertensive. Respondents with total cholesterol ≥ 240 mg/dl or low HDL cholesterol (< 40 mg/dl in men and < 50 mg/dl in women), or those who reported that they had been informed by a physician that they had high cholesterol were classified as having hyperlipidemia. Respondents who reported that they had been told by a health care provider that they had diabetes, were taking medications for diabetes or had fasting blood glucose ≥126 mg/dl were classified as having diabetes.
Statistical Analysis
We analyzed demographic, socioeconomic, clinical and motivational predictors of attempted weight loss, attempts at maintaining weight loss and successful weight loss using multivariate logistic regression. In the first step estimates were adjusted for age and sex. In the next step, demographic, socioeconomic, clinical and motivational variables were adjusted for. These variables included age, sex, ethnicity, poverty income ratio, medical insurance status, education level, smoking status, BMI, history of significant weight loss in the past, physician diagnosis of overweight, diabetes, hypertension, hyperlipidemia, awareness of overweight and desire to weigh less. We used SAS version 9.1 (SAS Institute, Inc, Cary, NC) and SUDAAN version 10.0 (Research Triangle Park, NC) for this analysis. (23) Because of complex sampling design of NHANES appropriate sampling weights, adjusted for multiple cycles of NHANES, were used. No extramural funding was used to support this work. The authors are solely responsible for the design and conduct of this study, all study analyses, the drafting and editing of the paper and its final contents.
RESULTS
Of the 16,731 non pregnant adult participants with available data on clinical and motivational factors of interest, 1,648 reported that they had been told by a physician that they had one or more of qualifying cardiovascular conditions (CHD, heart attack, heart failure and stroke).Of these 923 had body measurements done which permitted calculation of BMI and assessment of central obesity. Of these 923 participants, 907 had data that allowed calculation of weight loss over the preceding year. The 907 participants formed our final sample. The mean age of this sample was 64 years ± 0.82 (standard error). Distribution of demographic, socioeconomic, clinical and weight loss-related variables stratified by BMI (< and ≥ 30 kg/m2) are shown in Table 1.
table 1.
Demographic, socioeconomic, clinical and motivational characteristics in centrally obese adults with cardiovascular disease by BMI group *
| BMI < 30 N=389 |
BMI ≥ 30 N=518 |
|
|---|---|---|
| N (%) | N (%) | |
| Age categories, in years | ||
| Less than 50 | 25 (12) | 70 (20) |
| 50-65 | 81 (28) | 166 (35) |
| More than 65 | 283 (60) | 282 (45) |
| Gender | ||
| Male | 173 (42) | 252 (47) |
| female | 216 (58) | 266 (53) |
| Ethnicity | ||
| Caucasian | 261 (85) | 287 (77) |
| Hispanic | 76 (7) | 94 (6) |
| African American | 45 (6) | 124 (14) |
| Others | 7 (2) | 13 (3) |
| Poverty income ratio | ||
| Less than 1 | 58 (11) | 112 (20) |
| 1-2 | 119 (30) | 144 (28) |
| 2-3 | 59 (16) | 81 (18) |
| 3-4 | 44 (14) | 44 (13) |
| More than 4 | 77 (29) | 93 (21) |
| Education | ||
| Less than high school | 261 (61) | 354 (63) |
| High school or more | 128 (39) | 164 (37) |
| Smoker | ||
| Current smoker | 60 (23) | 69 (16) |
| Former smoker | 164 (38) | 233 (44) |
| Never smoker | 165 (40) | 216 (40) |
| Medically Insured | ||
| No | 29 (8) | 47 (9) |
| yes | 358 (92) | 463 (91) |
| Diabetes | ||
| No | 305 (82) | 336 (68) |
| yes | 82 (18) | 182 (32) |
| Hypertension | ||
| No | 99 (29) | 102 (23) |
| Yes | 290 (71) | 416 (77) |
| Hyperlipidemia | ||
| No | 151 (38) | 197 (39) |
| Yes | 238 (62) | 321 (61) |
| Aware of overweight status | ||
| No | 187 (39) | 54 (9) |
| Yes | 201 (61) | 464 (91) |
| Desirous of weighing less | ||
| No | 167 (34) | 48 (9) |
| Yes | 221 (66) | 470 (91) |
| Attempted weight loss | ||
| No | 267 (63) | 218 (41) |
| Yes | 122 (37) | 300 (59) |
| Tried to Maintain Weight | ||
| No | 259 (59) | 254 (46) |
| Yes | 130 (41) | 263 (54) |
| Lost ≥ 5% weight | ||
| No | 294 (85) | 411 (87) |
| Yes | 47 (15) | 78 (13) |
Seventy eight percent of the 907 centrally obese participants (n=665) were aware of their overweight status. Of the respondents who were aware of their overweight status, about 97% (n=643/665) wanted to weigh less, as opposed to only 23% (n=48/241) of respondents who did not consider themselves to be overweight (p <0.0001). Fifty seven percent (n=389/691) of individuals who wanted to weigh less, had actually attempted weight loss in the last year, as compared to 17% (n=32/215) of those who did not desire to weigh less (p <0.0001). Desire to weigh less was also associated with respondents trying to maintain their body weight in the preceding year. Fifty-five percent (n=358/690) of people desiring weight loss had tried to maintain their weight in the last year, compared to only 20% (n=36/215) of people who did not desire weight loss (p <0.0001). Among those who were aware of their overweight status, 13.3% had lost ≥5% weight in the last year (n= 101/639), unlike 14.7% respondents who did not consider themselves overweight (n=24/197) (p=0.70). Of those who were desirous of weighing less, 13.3% (104/661) had lost ≥5% weight in the last year, as opposed to 15.2% ( 21/175) of those who were not desirous of weighing less ( p=0.62).
Mean weight change in the whole sample during the preceding year was +0.87% ± 0.59 % (0.53 kg ± 1.14 kg), although 31% (n=279) of the sample had lost weight in the preceding year. Mean weight loss among those who had lost any weight was 8.43% ± 0.51% (8.20 kg ± 0.60 kg).
Age and sex-adjusted and multivariate predictors of attempted weight loss, attempts at weight maintenance and successful weight loss are shown in Tables 2 and 3. In age and sex-adjusted models Hispanic ethnicity, increasing income, diabetes, hypertension, increasing BMI, not having experienced significant weight loss prior to preceding year and desiring weight loss were significantly associated with successful weight loss. In multivariate models, Hispanic ethnicity, physician diagnosis of overweight, hypertension and not having experienced significant weight loss prior to preceding year were significant predictors of a weight loss ≥5%.
table 2.
Age and sex-adjusted odds ratios for attempted weight loss, attempts at not gaining weight and successful weight loss.
| Attempted weight loss OR ( 95% CI) |
Tried to maintain weight OR ( 95% CI) |
Successful weight loss OR ( 95% CI) |
|
|---|---|---|---|
| Age categories | |||
| Less than 50 | 1.49 (0.85-2.62) | 1.29 (0.71-2.34) | 0.81 (0.35-1.86) |
| 50-65 | 1.95 (1.34-2.82) | 1.48 (1.00-2.19) | 1.57 (0.93-2.66) |
| More than 65 (reference) | - | - | - |
| Gender | |||
| Male (reference) | - | - | - |
| Female | 1.20 (0.86-1.68) | 0.77(0.60-0.98) | 1.23 (0.75-2.03) |
| Ethnicity | |||
| Caucasian (reference) | - | - | - |
| Hispanic American | 0.99 ( 0.50-1.94) | 0.66 (0.36-1.18) | 3.29 (1.91-5.66) |
| African American | 1.18 (0.76-1.83) | 0.85 (0.57-1.28) | 1.85 (0.87- 3.93) |
| Others | 2.24 (0.58-8.66) | 1.10 (0.42-2.86) | 2.61 (0.99-6.85) |
| Poverty income ratio | |||
| Less than 1 (reference) | - | - | - |
| 1-2 | 1.11 (0.68-1.79) | 1.06 (0.66-1.69) | 0.77 (0.34-1.73) |
| 2-3 | 1.41 (0.87-2.28) | 2.08 (1.33-3.25) | 0.42 (0.19-0.96) |
| 3-4 | 1.05 (0.53-2.06) | 1.97 (1.02-3.79) | 0.11 (0.03-0.39) |
| More than 4 | 1.55 ( 0.90-2.69) | 2.42 (1.47-3.99) | 0.69 (0.29-1.61) |
| Medically Insured | |||
| No (reference) | - | - | - |
| Yes | 1.76 (0.91-3.42) | 2.10 (1.08-4.06) | 0.80 ( 0.31-2.11) |
| Education | |||
| Less than high school(reference) | - | - | - |
| More than high school | 1.42 (1.00-2.03) | 1.82 (1.28-2.59) | 1.09 (0.58-2.04) |
| Smoking status | |||
| Never smoker(reference) | - | - | - |
| Former smoker | 1.70 (1.08-2.67) | 1.15 (0.77-1.95) | 0.59 (0.36-0.97) |
| Current smoker | 0.96 (0.55-1.68) | 0.88 (0.51-1.51) | 0.92 (0.44-1.91) |
| BMI | |||
| Less than 30 (reference) | - | - | - |
| 30-40 | 1.66 (1.07-2.56) | 1.40 (0.90-2.17) | 4.30 (1.98-9.32) |
| More than 40 | 5.50 (1.78-17.00) | 1.72 (0.88-3.36) | 19.19 (6.38 - 57.67) |
| Successful weight loss in past | |||
| No (reference) | - | - | - |
| yes | 1.03 (0.73-1.46) | 1.15 (0.81-1.63) | 2.79 (1.66-4.70) |
| Time since maximum weight ( years) | 0.98 (0.97-0.99) | 0.99 (0.98-1.0) | 1.01 (0.99-1.02) |
| Physician diagnosis of overweight | |||
| No (reference) | - | - | - |
| yes | 3.18 (2.32-4.37) | 2.31 (1.55-3.45) | 2.23 (1.30-3.81) |
| Diabetes | |||
| No (reference) | - | - | - |
| Yes | 1.53(1.00-2.34) | 1.18(0.81-1.72) | 1.90 (1.14-3.17) |
| Hypertension | |||
| No (reference) | - | - | - |
| Yes | 1.43 (0.88-2.33) | 0.94 (0.59-1.47) | 2.80 (1.16-6.75) |
| Dyslipidemia | |||
| No(reference) | - | - | - |
| Yes | 1.06 (0.67-1.67) | 0.83 (0.52-1.33) | 0.63 (0.34-1.14) |
| Awareness of overweight | |||
| No (reference) | - | - | - |
| Yes | 4.57 (2.71-7.70) | 2.98 (1.97-4.51) | 0.82 (0.42-1.59) |
| Desirous of weighing less | |||
| No (reference) | - | - | - |
| Yes | 5.47 (3.14-9.54) | 4.71 (2.97-7.46) | 0.71 (0.35-1.41) |
table 3.
Multivariable logistic regression for attempts at losing weight, attempts at maintaining weight and successful weight loss.
| covariate | Attempted weight loss N=802 OR ( 95% CI) |
Tried to maintain weight N=803 OR ( 95% CI) |
Successful weight loss N=740 OR ( 95% CI) |
|---|---|---|---|
| Age categories | |||
| Less than 50 | 1.47 (0.66- 3.25) | 1.19 (0.56-2.53) | 0.97 (0.32-2.94) |
| 50-65 | 1.69 (1.11-2.56) | 1.30 (0.80-2.11) | 1.99 (0.96-4.13) |
| More than 65 (reference) | - | - | - |
| Gender | |||
| Male (reference) | - | - | - |
| Female | 1.31 (0.93-1.86) | 0.84 (0.58-1.20) | 1.04 (0.51-2.13) |
| Ethnicity | |||
| Caucasian (reference) | - | - | - |
| Hispanic American | 1.21 (0.55-2.66) | 0.73 (0.39-1.36) | 2.57 (1.27-5.19) |
| African American | 1.58 (0.95-2.62) | 1.13 (0.66-1.93) | 1.54(0.64-3.71) |
| Others | 2.40 (0.77-7.50) | 0.71 (0.36-1.39) | 2.03 (0.84-4.90) |
| Poverty income ratio | |||
| Less than 1 (reference) | - | - | - |
| 1-2 | 1.09 (0.63-1.89) | 0.76 (0.46-1.25) | 1.08 (0.50-2.34) |
| 2-3 | 1.10(0.55-2.20) | 1.37 (0.84- 2.22) | 0.59 (0.24-1.44) |
| 3-4 | 1.06 (0.49-2.29) | 1.35 (0.66-2.75) | 0.12 (0.03-0.50) |
| More than 4 | 1.31 (0.60-2.90) | 1.38 (0.73-2.62) | 0.72 (0.28-1.85) |
| Education | |||
| Less than high school (reference) | - | - | - |
| More than high school | 1.33 (0.87- 2.04) | 1.56 (1.07-2.27) | 1.36 (0.65- 2.84) |
| Smoking status | |||
| Never smoker (reference) | - | - | - |
| Former smoker | 1.63 (0.97-2.73) | 0.98 (0.61-1.57) | 0.58 (0.34-0.98) |
| Current smoker | 1.28 (0.67-2.48) | 1.08 (0.62-1.89) | 0.89 (0.41-1.96) |
| Medically Insured | |||
| No (reference) | - | - | - |
| Yes | 1.40(0.63-3.08) | 1.96(0.90-4.28) | 1.02 (0.37-2.82) |
| BMI category | |||
| 25-30 (reference) | - | - | - |
| 30-40 | 1.11 (0.64-1.93) | 0.91 (0.56-1.48) | 0.56 (0.30-1.05) |
| More than 40 | 1.43 (0.53-3.85) | 0.99 (0.48-2.01) | 0.46 (0.14-1.49) |
|
History of significant weight
loss in past (>5 percent) |
|||
| Yes (reference) | - | - | - |
| No | 1.04 (0.66-1.64) | 1.21 (0.80-1.83) | 4.69 (2.45-8.96) |
| Time that has elapsed since maximum weight ( years) |
1.0 ( 0.98-1.01) | 1.0 (0.99-1.01) | 1.02 (1.0-1.4) |
|
Physician diagnosis of
overweight |
|||
| No (reference) | - | - | - |
| yes | 2.31 (1.33-4.00) | 2.49 (1.72-3.62) | 2.78 (1.37-5.63) |
| Diabetes | |||
| No (reference) | - | - | - |
| Yes | 1.19(0.71-1.98) | 1.12 (0.69-1.82) | 1.45 (0.83-2.53) |
| Hypertension | |||
| No (reference) | - | - | - |
| Yes | 1.10(0.67-1.82) | 0.72 ( 0.45-1.15) | 2.39 (1.00-5.72) |
| Hyperlipidemia | |||
| No (reference) | - | - | - |
| Yes | 1.18 (0.80-1.75) | 0.88 (0.58-1.32) | 0.93 (0.49-1.74) |
| Awareness of overweight | |||
| No (reference) | - | - | - |
| yes | 1.38 (0.58-3.28) | 0.64 (0.26-1.54) | 0.92(0.27-3.12) |
| Desirous of weighing less | |||
| No (reference) | - | - | - |
| Yes | 3.37(1.51-7.52) | 5.11 (2.25-11.61) | 0.89 (0.26-3.05) |
All models are adjusted for age, gender, ethnicity, poverty income ratio, education, smoking, Insurance status, BMI, diabetes, hypertension, hyperlipidemia, history of cardiovascular disease, weight loss history, awareness of overweight and desire to weigh less
BMI calculated by using self reported weight one year prior was associated with weight change. Mean percent weight change in those with BMI < 30 kg/m2 was +2.8 %, 30-40 kg/m2 −0.26% and for BMI > 40 kg/m2 −5.24% (p for trend < 0.0001). In age and sex-adjusted models, BMI one year prior was significantly predictive of successful weight loss as well (results not shown). Mean weight change among those who had been told by physicians that they were overweight was −1.06 kg ± 1.58 kg, as compared to −0.20 kg ± 1.33 kg in those who had not been informed by physicians about their overweight status ( p= <0.001). Respondents who reported that they had been informed by physicians of their overweight status were almost three times as likely to be successful in having lost ≥5% of their body weight over the preceding year (2.78, 95% CI 1.37-5.63, p=0.006).
Given that respondents reporting that a physician or health care provider had informed them of their overweight status emerged as an important predictor of successful weight loss, we also examined which demographic and clinical factors were associated with respondent-reported physician diagnosis of overweight. Results are shown in Table 4. Respondents with diabetes and a higher BMI were significantly more likely to report that they had been told by physician that they were overweight.
table 4.
Predictors of physician diagnosis of overweight in centrally obese patients with CVD
| Physician informed participants they were overweight (n=560) n ( %) |
Physician did not inform them that they were overweight (n=347) n (%) |
P | |
|---|---|---|---|
| Age categories | |||
| Less than 50 | 66 (18) | 29 (15) | 0.40 |
| 50 to 65 | 172 (33) | 75 (30) | |
| More than 65 | 322 (49) | 243 (55) | |
| Gender | |||
| Male | 270 (47) | 155 (43) | 0.29 |
| Female | 290 (53) | 192 (57) | |
| Ethnicity | |||
| Caucasian | 318 (79) | 230 (83) | 0.40 |
| Hispanic | 115 (7) | 55 (5) | |
| African American | 113 (12) | 56 (9) | |
| Others | 14 (2) | 6 (3) | |
| Poverty income ratio | |||
| Less than 1 | 109 (16) | 61 (15) | |
| 1-2 | 158 (30) | 105 (27) | 0.49 |
| 2-3 | 88 (17) | 52 (17) | |
| 3-4 | 50 (11) | 38 (16) | |
| More than 4 | 105 (25) | 65 (25) | |
| Education | |||
| Less than high school | 375 (34) | 240 (64) | 0.80 |
| High school or more | 185 (38) | 107 (36) | |
| Medically Insured | |||
| Yes | 498 (91) | 323 (92) | 0.68 |
| No | 52 (9) | 24 (8) | |
| Smoker | |||
| Current smoker | 72 (16) | 57 (23) | 0.06 |
| Former smoker | 256 (44) | 141 (38) | |
| Never smoker | 232 (40) | 149 (39) | |
| Self reported BMI kg/m2 | |||
| Less than 30 | 186 (34) | 263 (75) | <0.0001 |
| 30 -40 | 327 (55) | 78(24) | |
| More than 40 | 46 (11) | 4 (1) | |
| Actual BMI kg/m2 | |||
| Less than 30 | 24 (141) | 72 (248) | <0.0001 |
| 30 -40 | 65 (354) | 27 (94) | |
| More than 40 | 12 (65) | 2 (5) | |
| Diabetes | |||
| No | 68 ( 359) | 83 ( 282) | 0.0001 |
| Yes | 32 ( 200) | 17 ( 64) | |
| Hypertension | |||
| No | 22(110) | 32(91) | 0.01 |
| Yes | 78(450) | 68(256) | |
| Dyslipidemia | 0.09 | ||
| No | 35(199) | 198 (57) | |
| Yes | 65(361) | 149 (43) |
DISCUSSION
Our results suggest that weight loss in centrally obese cardiovascular patients entails complex clinical and cognitive determinants. Despite the impact of central obesity on cardiovascular health, only 59% of respondents in this nationally representative sample had attempted weight loss in the preceding year. Furthermore, of these only 26% of participants had been successful in losing ≥5% of their body weight. New tailored effective interventions need to be developed for this prevalent and refractory problem of abdominal obesity.
About two-thirds of respondents reported that they had been informed of their overweight status by physicians. Our results are keeping with existing literature that suggests poor documentation of obesity as a diagnosis, and also poor documentation of an obesity management plan in overweight patients with cardiovascular disease, especially after MI.(12) In this analysis younger, more obese and diabetic participants were more likely to report that they had been diagnosed with overweight by physicians. This becomes more important in light of our finding that adults who reported that they had been told by their physician that they were overweight, were more likely to attempt weight loss and successfully lose weight. Data from Behavioral Risk Factor Surveillance Survey (BRFSS) have shown that physician advice about weight loss is associated with increased attempts at losing weight.(24-26) Our analysis extends findings from prior population-based studies by showing that physicians diagnosis of overweight was associated with significant (≥5%) weight loss in the preceding year. (27)
Interestingly, Hispanic Americans in the sample had higher odds of being successful at having significant weight loss. Often research has shown that under-represented groups will have more negative health behaviors that will result in worse health outcomes.(28) More investigation to explore ethnic differences in successful weight loss in CVD patients is needed.
Mean weight loss in our sample is small and consistent with the study published by Fadl and colleagues who reported only slight weight loss (0.2 %) in post-MI patients after one year. They also found that degree of weight loss in MI survivors was dependent on participants’ initial grade of obesity. In our analysis as well, participants who had a BMI ≥30 kg/m2 one year before they were surveyed lost more weight than participants with BMI <30 kg/m2. This could be due to greater social pressures to lose weight, or even greater differential recall of one’s weight a year ago by more overweight respondents. It is important also to look at motivational status of these respondents. The majority, almost 90% of centrally obese participants with a BMI >30 kg/m2 were aware of their overweight status and wanted to weigh less; but only about half of these obese adults attempted to lose weight. Thus it appears that obese adults with cardiac disease and central obesity know that losing weight would be beneficial, but for unknown reasons most do not start a weight loss program. In a survey of adults in the community we found that while many overweight and obese adults wanted to lose weight, only a very small proportion combined caloric restriction and physical activity into their weight loss attempts.(29)
Motivational factors (awareness of overweight and desire to weigh less) emerged as important determinants of attempts at losing weight and not gaining weight in both age and sex-adjusted and multivariate models. However, no significant association of motivational factors with successful weight loss was found in this analysis. Intuitively, lack of an association of successful weight loss in the preceding year with self-perception of overweight and desire to weigh less, which was assessed at the time of interview, might be expected. The motivational variables reported here are analogous to the stages of change (precontemplation, contemplation, preparation, action and maintenance) as described in the Transtheoretical Model, which is well supported in smoking literature.(30, 31) However, few studies have shown that the Transtheoretical Model might lack predictive utility for weight loss. To the best of our knowledge, this is the first analysis that explores the association of motivational factors with successful weight loss in patients with cardiovascular disease. Previously Kant and colleagues have reported association between motivational factors (except successful weight loss) in overweight adolescents using data from NHANES.(32)
Respondents who achieved ≥5 % weight losses ever were less likely to experience significant weight loss over the past year. Moreover, successful weight loss in the preceding year had a direct relationship with elapsed time since participants had reached their maximum weight. This supports existing literature from NHANES and National Weight Control Registry which suggests that weight regain is more common in those who had lost a greater percentage of their body weight.(33)
Our study is not without limitations. The question used to assess participants’ self perception about overweight status is subject to self-interpretation, and information about what the word ‘overweight’ meant to respondents was not collected. We used self-reported body weights for calculating weight loss, and these are subject to errors and reporting biases which could vary by age, gender, ethnicity and overweight status.(34) Temporal or causal relationship of physician diagnosis with weight loss attempts cannot be assumed, even though the association may be strong. Our study and the available data lack information on mechanisms by which physician diagnosis could have led to increased weight loss attempts and successful weight loss. The survey question only asked whether the respondents had been informed of their overweight status by a physician. Information about the physician encounter where respondents were informed about their overweight status is not available in NHANES. Hence it cannot be concluded if making a diagnosis of overweight was accompanied with a discussion of behaviors to promote weight loss.
Motivational factors were assessed at the time of interviewing and not a year prior to the interview before initiation of weight loss attempts. Hence, temporal transition between stages of change, per the Transtheroretical Model proposed by Prochaska and colleagues cannot be verified. Moreover, standardized instruments to measure each stage of change were not employed in NHANES. An important limitation of our analysis is that motivation of respondents to weigh less may have influenced their recall about physician diagnosis of overweight. In a cross-sectional study of outpatients, Flocke et al have shown that only 43-44% of patients actually were able to recall that a physician had given them advice about diet and exercise(35). Although demographic factors were not associated with recall, the time physician spent counseling was predictive of recall. Details on motivational characteristics were not evaluated in this study.
Our study also does not examine association of motivational factors and weight loss with depression and dysthymia in the community.(36) Unfortunately, depressive symptoms were evaluated in respondents aged 20-39 years in NHANES, and data on most cardiovascular patients was not available. Self-efficacy, an important factor that facilitates behavioral change, measures people’s beliefs about their capabilities to produce designated levels of performance and a powerful predictor of successful weight loss and weight maintenance, (33) was not measured in NHANES.
Inspite of these limitations, our results underscore the important role that physicians may play in promoting weight loss in patients with cardiovascular disease. Increased recognition of obesity in cardiovascular patients and counseling by physicians may promote weight loss. Only randomized clinical trials may confirm a causal relationship and dose response between office-based physician counseling and weight loss in patients with CHD. Ideally, those studies should also identify the mechanisms through which a relatively brief office-based recommendation may induce behavioral change, and compare different ways to deliver the advice.
CONCLUSION
Our study adds to the growing literature about diagnosis and treatment of obesity in a broad spectrum of patients with cardiovascular disease. Physician diagnosis of overweight was associated not only with participants recognizing themselves as overweight; it was also predictive of participants desiring and attempting weight loss, participants trying to not gain weight and actually succeeding in losing their weight in a 12-month period. More research using prospective design is needed to confirm these associations.
ABBREVIATIONS
- NHANES
National Health and Nutritional Examination Survey
- NCHS
National Center for Health Statistics
- BMI
Body mass index
- ATP
Adult Treatment Panel
- CHD
Coronary Heart Disease
Footnotes
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