Role of Fitness in the Metabolically Healthy but Obese Phenotype: A Review and Update

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Abstract

Despite the strong and consistent evidence supporting that a high physical fitness (PF) level at any age is a major predictor of a healthier metabolic profile, major studies focused on the metabolically healthy but obese (MHO) phenotype have ignored the role of PF when examining this phenotype and its prognosis. Particularly, the role of its main health-related components such as higher cardiorespiratory fitness (CRF) and muscular fitness in the MHO phenotype needs to be reviewed in depth. The present review aimed to: 1) contribute to the characterization of the MHO phenotype by examining whether MHO individuals are fitter than metabolically abnormal obese (MAO) individuals in terms of CRF and other PF components; 2) review the role of CRF and other PF components in the prognosis of MHO. The studies reviewed suggest that a higher CRF level should be considered a characteristic of the MHO phenotype. Likewise, CRF seems to play a key role in the prognosis of the MHO individuals, yet this statement is based on a single study and future studies need to confirm or contrast these findings. Comparability of studies is difficult due to the different definitions used for MHO; consequently, the present review makes a proposal for harmonizing this definition in adults and in youth. Obesity is still related to an important number of comorbidities; therefore, the public health message remains to fight against both obesity and low CRF in both adult and pediatric populations.

Section snippets

Overall description of the studies reviewed

We found 12 studies in which any of the components of PF were compared between MHO and MAO. The most relevant information from each of these studies is presented in Table 1. In addition, a summary of the characteristics of these studies is shown in Table 2. Surprisingly, 75% of the studies focused exclusively on women20., 21., 22., 24., 26., 27., 28., 29., 30. and only 25% focused on both women and men (no study was focused only in men).31., 33., 34. Likewise, all studies20., 21., 22., 24., 26.

Does PF influence the prognosis of MHO? Current evidence from prospective longitudinal data

From a public health and clinical point of view, the most relevant question is related to the prognosis of MHO individuals when compared with MAO individuals and also when compared with normal-weight individuals. The present review identified only one study, conducted by our group, that explored the role of CRF (no study examining other PF components) in relation with the prognosis of MHO.34 In that study, we observed that when models were not adjusted for CRF, the results suggested that

Proposal of a harmonized definition of the MHO and MAO phenotypes

While reviewing the existing literature on MHO individuals, it became clear that a harmonized definition of the MHO was highly needed. A standardized definition of MHO would increase the comparability of the data, allowing accurate meta-analyses in the future. Based on several facts, we hereby propose a harmonized definition of the MHO and MAO phenotypes (Table 3).

Future directions

In addition to the need of a harmonized MHO definition, several future directions for research have been identified in this review: 1) more investigation is needed for a better understanding of the interrelationship between MHO and cardiorespiratory fit obese phenotypes50; 2) whether the differences in PF between MHO and MAO differ by gender and whether the role of PF in the prognosis of MHO differ by gender are unknown and need to be addressed; 3) there is a need for further study on the role

Conclusions

The studies reviewed suggest that a higher CRF level should be considered a characteristic of the MHO phenotype. Likewise, CRF seems to play a key role in the prognosis of the MHO individuals, yet this statement is based on a single study and future studies are needed to confirm or contrast these findings. In a perfect world, all individuals would be fit and metabolically healthy at any weight.

Acknowledgments

FBO was supported by a grant from the Spanish Ministry of Science and Innovation – MINECO (RYC-2011-09011). CCS is supported by a grant from the Spanish Ministry of Economy and Competitiveness (BES-2014-068829).

References (50)

  • P.A. McAuley et al.

    The obesity paradox, cardiorespiratory fitness, and coronary heart disease

    Mayo Clin Proc

    (2012)
  • C.J. Lavie et al.

    Impact of cardiorespiratory fitness on the obesity paradox in patients with heart failure

    Mayo Clin Proc

    (2013)
  • C.J. Lavie et al.

    Obesity and cardiovascular diseases: implications regarding fitness, fatness, and severity in the obesity paradox

    J Am Coll Cardiol

    (2014)
  • A. De Schutter et al.

    The impact of obesity on risk factors and prevalence and prognosis of coronary heart disease-the obesity paradox

    Prog Cardiovasc Dis

    (2014)
  • V.W. Barry et al.

    Fitness vs. fatness on all-cause mortality: a meta-analysis

    Prog Cardiovasc Dis

    (2014)
  • A.S. Babu et al.

    Metabolically healthy obese versus cardiorespiratory fit obese: is it time to bring them together?

    J Am Coll Cardiol

    (2014)
  • G. Högström et al.

    High aerobic fitness in late adolescence is associated with a reduced risk of myocardial infarction later in life: a nationwide cohort study in men

    Eur Heart J

    (2014)
  • M. Sato et al.

    Physical fitness during adolescence and adult mortality

    Epidemiology

    (2009)
  • S. Kodama et al.

    Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis

    JAMA

    (2009)
  • J.V. Van Vliet-Ostaptchouk et al.

    The prevalence of metabolic syndrome and metabolically healthy obesity in Europe: a collaborative analysis of ten large cohort studies

    BMC Endocr Disord

    (2014)
  • S. Bokor et al.

    Prevalence of metabolic syndrome in European obese children

    Int J Pediatr Obes

    (2008)
  • V. Primeau et al.

    Characterizing the profile of obese patients who are metabolically healthy

    Int J Obes

    (2011)
  • C.K. Kramer et al.

    Are metabolically healthy overweight and obesity benign conditions?: a systematic review and meta-analysis

    Ann Intern Med

    (2013)
  • C.J. Lavie et al.

    Metabolically healthy obesity, fitness, and prognosis

    Ochsner J

    (2015)
  • M. Blüher

    Are metabolically healthy obese individuals really healthy?

    Eur J Endocrinol

    (2014)
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    Competing interests: The authors have declared that no competing interests exist.

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