Annals of African Medicine

: 2012  |  Volume : 11  |  Issue : 4  |  Page : 212--216

The "Obesity Paradox" in Nigerians with heart failure

Adebayo T Oyedeji, Michael O Balogun, Anthony O Akintomide, TA Sunmonu, Rasaaq A Adebayo, Olufemi E Ajayi 
 Department of Medicine, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Osun, Nigeria

Correspondence Address:
Adebayo T Oyedeji
Department of Medicine, Osun State University, Osogbo


Background: Previous studies have suggested that a high body mass index (BMI) was associated with improved outcome in congestive heart failure (CHF). The aim of this study was to examine the relationship between BMI and echocardiographic variables of cardiac function in stable outpatients with heart failure. Methods and Materials: This is a cross-sectional study in which the cardiology clinic out-patients of Obafemi Awolowo University Teaching Hospital with heart failure were recruited. Patients were categorized using baseline BMI as normal weight BMI = 18.5-24.9 kg/m 2 and overweight/obese (BMI > 25.0 kg/m 2 ). Risks associated with BMI groups were evaluated and the data were analyzed with the aid of SPSS 15.0 software. Results: Patients with higher BMI have higher left ventricular ejection fraction and fractional shortening and lesser tendency to have an abnormal left ventricular geometry and better functional (New York Heart Association) class of heart failure at presentation. Conclusion: Overweight and obese patients had less severe degree of heart failure than normal weight patients and efforts should be made to prevent excessive weight loss in patients with heart failure.

How to cite this article:
Oyedeji AT, Balogun MO, Akintomide AO, Sunmonu T A, Adebayo RA, Ajayi OE. The "Obesity Paradox" in Nigerians with heart failure.Ann Afr Med 2012;11:212-216

How to cite this URL:
Oyedeji AT, Balogun MO, Akintomide AO, Sunmonu T A, Adebayo RA, Ajayi OE. The "Obesity Paradox" in Nigerians with heart failure. Ann Afr Med [serial online] 2012 [cited 2022 Oct 5 ];11:212-216
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Full Text


Obesity is a major risk factor for cardiovascular disease such as hypertension, coronary artery disease, and chronic kidney diseases. [1] Epidemiological studies have shown a strong relationship between obesity and increased risk of cardiovascular disease and mortality in the general population. [2],[3] Obesity has numerous adverse effects on cardiac function such as expanded intravascular volume which result in increased cardiopulmonary volume or increased preload. These changes lead to increased propensity to eccentric left ventricular hypertrophy and complex ventricular dysrrhythmias overtime.

Recent epidemiological studies showed that obesity is a potent predictor of subsequent abnormalities in diastolic and systolic function and predisposes to heart failure (HF); however obese patients with HF paradoxically tend to have a more favorable clinical prognosis. [2],[3],[4],[5],[6],[7],[8],[9],[10] There is paucity of studies on the relationship between the body mass index (BMI) and HF in Nigerians with heart failure and hence the need for this study.

 Materials and Methods

Patients were categorized using baseline body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meter) as normal/healthy weight (BMI, 18.5-24.9 kg/ m 2 ) and overweight/obese (BMI ≥25.0 kg/m 2 ). Each participant underwent a transthoracic echocardiographic examination with Siemens Sonoline G 60S equipment according to standard protocols between January and December 2006. Two-dimensional apical four- and two-chamber views were used for all participants, supplemented by parasternal long- and short-axis views. Systolic function was evaluated by an experienced cardiologist and two senior registrars. Left ventricular ejection fraction was expressed as the average values between observers. EF was estimated by the Teichholz method while left atrial and left ventricular dimensions were determined by M-mode echocardiography in the parasternal long-axis view.

Statistical analysis

Continuous variables were expressed as mean ± 1SD and categorical variables as percentages. The associations of the two categories of weight with cardiac function were assessed in univariate analysis using the Chi-square and Student's t-tests, respectively. A P value<0.05 was considered significant with multivariate regression analysis.


Ninety-one patients with heart failure participated in the study. The patients were divided into two groups: Overweight/obese patients and patient with normal BMI. The mean age of the obese patients was 56.30+12.17 years while that of patients with normal BMI was 62.42+ 10.52 years. The other aspects of the demographic details and clinical laboratory parameters of the subjects are summarized in [Table 1].{Table 1}

The etiology of heart failure is summarized in [Table 2]. Systemic hypertension accounted for majority (76.9%) of the cases of HF. This was followed by dilated cardiomyopathy (12.1%) and valvular heart disease (9.9%). Ischemic heart disease was responsible for one case (1.1%).{Table 2}

The echocardiographic findings of the overweight obese patients were compared with normal weight patients and the results are summarized in [Table 3].{Table 3}

The pattern of left ventricular geometry in the study participants are highlighted in [Table 4].{Table 4}

Abnormal left ventricular geometry (concentric and eccentric hypertrophy) occurred more frequently in the healthy weight patients compared with overweight/obese patients; 85% versus 65%.


Obesity is a major medical problem in western society and is becoming an emerging problem in developing countries of the world recently. Recent epidemiological studies had shown increased prevalence of obesity and congestive heart failure (CHF) in the western world and indeed, 29-62% of CHF patients were overweight [6],[9],[11],[12] and 15-37% were obese. [6],[10],[13] In the general population, obesity is associated with increased mortality [14],[15] but paradoxically, a positive correlation between BMI and survival in CHF has been documented. [2],[6],[9]

This study showed that the obese patients had better systolic function when compared to normal controls corroborating the findings from the study by Kenchaiah et al.[5] where increased BMI was associated with significantly high left ventricular ejection fraction and fractional shortening. In the study by Gustafsson et al.[1] where 4700 patients with heart failure and varying BMI were studied, significant LV systolic dysfunction was less common in the obese patients which is in keeping with this present findings. However in this study the diastolic function parameters (such as isovolumic relaxation time and deceleration time) were similar across the various BMI groups in the patients and this is in sharp contrast to the findings of some authors where diastolic dysfunction is more prevalent in obese patients even in those without history of prior heart disease. [16],[17] Alpert et al. [18],[19],[20] have confirmed the deleterious effect of significant of obesity on both systolic and diastolic functions.

Excessive weight has been associated with dyslipidemia (as in this study), hypertension, and diabetes. [21] In addition obesity is associated with left ventricular hypertrophy, increased left ventricular systolic and diastolic dimensions, and increased cardiac output. [22] Though population-based studies have found elevated BMI to independently increase cardiovascular risk for heart failure [5],[23] but other studies stated that obesity might actually be associated with better outcomes (obesity paradox). [7],[9],[10],[11] In thisstudy the obese patients presented with significantly lower rate of severe heart failure when compared to the patients with heart failure with normal weight and this is in keeping with the above studies. [9],[10],[11] Also, dangerous arrhythmias such as ventricular premature complexes and atrial fibrillation were less common in the obese patients when compared to patients with normal weight and HF in this study. A review of six studies by Kalantar-Zadeh et al. [3] demonstrated that among patients with HF, obesity appeared to be associated with a better overall prognosis and patients with more severe HF tend to have lower BMI than do age- and gender- matched obese patients with HF. Horwich et al. [6] studied 1203 individuals with mostly NYHA Class IV HF and found that a higher BMI was associated with better survival rate and in multivariate analysis there was an inverse relationship between BMI and mortality. A study of 209 patients with mostly class II and III HF and a mean ejection fraction of only 23% showed that higher BMI and higher percentage body fat were associated with better event-free survival during a 2-year follow-up. [7] In advanced HF, cachexia, and wasting appears to be an independent predictor of increased mortality. [24],[25],[26] Some other studies, however, showed that obesity may be protective in heart failure only in the patients with more preserved systolic function and that patients with more systolic dysfunction may not have a better clinical prognosis [1] though many of the patients in these studies were much older, have more renal dysfunction, atrial fibrillation, smoking, obstructive lung diseases, and lower use of angiotensin converting enzyme inhibitors. In a study by Davos et al. [11] better outcomes were observed with increasing BMI and there was a nonsignificant trend to worsened outcomes in the heaviest quartile (BMI 34.1+2.8) but in a more recent study by Kapoor et al. [27] which evaluated 1236 patients with prior heart failure and preserved ejection fraction (≥50%) it was found out that there was increased mortality in obese patients with BMI >45 kg/m 2 with heart failure and that the highest mortality were in the lowest and highest weight individuals raising the possibility of a U-shaped relationship between BMI and clinical prognosis in heart failure. Other arguments against the obesity paradox in heart failure was the fact that purposeful weight loss in HF with morbid obesity has been associated with improvement in systolic and diastolic function and HF classification [5] but no large studies have determined the impact of purposeful weight reduction on HF prognosis and mortality in either patients with preserved or abnormal systolic function.

The relationship between HF and obesity is unlikely to be causal. Some authors have suggested that many mechanisms could be involved in the protective effect of obesity on the severity of HF. Some authors have demonstrated that lean adjusted exercise indices (including peak oxygen consumption, anaerobic threshold, and oxygen pulse) are higher in the obese HF patients. [28] Some serum biomarkers have also been demonstrated to play active role in the protective effect of obesity on HF. Soluble tumor necrosis factor and receptors which are elevated in heart failure are produced by adipose tissue and may neutralize the untoward effects of tumor necrosis factor. [28],[29] Elevated levels of catecholamines, transforming growth factor ß, interferon Y, tumor necrosis factor alpha, and interleukins 1 and 6 have been associated with the wasting syndrome of cardiac cachexia observed in advanced heart failure that is typified by weight loss and adverse outcomes. [24],[26],[27],[28],[29],[30] Other potential reasons for the protective effect of obesity on HF is the reduced renin-angiotensin activity that are lower with obesity. [30],[31] Several studies suggested that the natriuretic peptide system and adiposity are closely linked and a reduced natriuretic peptide level was demonstrated in obese patients with heart failure. [4]

A protective effect of higher BMI has also been reported in other medical conditions such as ischemic heart disease, [30],[32] advanced age [33] chronic obstructive pulmonary disease [34] and end-stage renal disease, and cancers. [3]

Understanding the mechanisms and impact of the "obesity paradox" in patients with HF is necessary before recommendations are made concerning weight and weight control in this population.

In conclusion this study has shown that obese patients with heart failure have better systolic function than normal weight patients with heart failure. In addition, HF patients with normal BMI have higher rate of development of abnormal left ventricular geometry.


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