Are Metabolically Healthy Overweight and Obesity Benign Conditions?: A Systematic Review and Meta-Analysis

Ann Intern Med. 2013 Dec 3;159(11):758-69. doi: 10.7326/0003-4819-159-11-201312030-00008.

Abstract

Background: Recent interest has focused on a unique subgroup of overweight and obese individuals who have normal metabolic features despite increased adiposity. Normal-weight individuals with adverse metabolic status have also been described. However, it remains unclear whether metabolic phenotype modifies the morbidity and mortality associated with higher body mass index (BMI).

Purpose: To determine the effect of metabolic status on all-cause mortality and cardiovascular events in normal-weight, overweight, and obese persons.

Data sources: Studies were identified from electronic databases.

Study selection: Included studies evaluated all-cause mortality or cardiovascular events (or both) and clinical characteristics of 6 patient groups defined by BMI category (normal weight/overweight/obesity) and metabolic status (healthy/unhealthy), as defined by the presence or absence of components of the metabolic syndrome by Adult Treatment Panel III or International Diabetes Federation criteria.

Data extraction: Two independent reviewers extracted the data. Metabolically healthy people of normal weight made up the reference group.

Data synthesis: Eight studies (n = 61 386; 3988 events) evaluated participants for all-cause mortality and/or cardiovascular events. Metabolically healthy obese individuals (relative risk [RR], 1.24; 95% CI, 1.02 to 1.55) had increased risk for events compared with metabolically healthy normal-weight individuals when only studies with 10 or more years of follow-up were considered. All metabolically unhealthy groups had a similarly elevated risk: normal weight (RR, 3.14; CI, 2.36 to 3.93), overweight (RR, 2.70; CI, 2.08 to 3.30), and obese (RR, 2.65; CI, 2.18 to 3.12).

Limitation: Duration of exposure to the metabolic-BMI phenotypes was not described in the studies and could partially affect the estimates.

Conclusion: Compared with metabolically healthy normal-weight individuals, obese persons are at increased risk for adverse long-term outcomes even in the absence of metabolic abnormalities, suggesting that there is no healthy pattern of increased weight.

Primary funding source: Intramural funds from the Leadership Sinai Centre for Diabetes.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Adult
  • Body Mass Index
  • Body Weight / physiology
  • Cardiovascular Diseases / complications*
  • Cardiovascular Diseases / mortality
  • Cause of Death*
  • Female
  • Humans
  • Male
  • Metabolic Syndrome / complications
  • Obesity / complications*
  • Obesity / metabolism
  • Obesity / mortality
  • Overweight / complications*
  • Overweight / metabolism
  • Overweight / mortality
  • Risk Factors