Life course factors associated with metabolically healthy obesity: a protocol for the systematic review of longitudinal studies

Prevalence of metabolically healthy obesity and healthy overweight and the associated factors in southern Iran: A population-based cross-sectional study

Background and Aims

Obesity is considered a major growing threat to public health which could negatively affect the quality of life. The current cross-sectional study was conducted to investigate the population-based prevalence of metabolically healthy obesity (MHO) and healthy overweight (MHOW) and associated factors in southern Iran.

Methods

Baseline data from the Pars Cohort Study was analyzed. Metabolically healthy participants were identified based on the definition of the American Heart Association for the metabolic syndrome. The prevalence of MHOW and MHO and their 95% confidence intervals were estimated. Poisson regression was applied for the calculation of prevalence ratios (PRs).

Results

Gender- and age-standardized prevalences of MHOW and MHO were 6.3% (6.0%-6.6%) and 2.3% (2.1%-2.5%), respectively. The following factors were associated with being MHOW compared with those with normal weight: Being younger, female gender (1.31, 1.20-1.43), higher socioeconomic status, being noncurrent cigarette smoker (1.27, 1.11-1.45), low level of physical activity (1.14, 1.03-1.25), having normal overweight during adolescence, and overweight (1.35, 1.24-1.48) or obesity (1.68, 1.53-1.86) during young adulthood. We also found strong associations between MHO and younger age groups, female gender (2.87, 2.40-3.42), being married (1.57, 1.08-2.27), Fars ethnicity (1.25, 1.10-1.43), higher socioeconomic status, ever use of tobacco (1.14, 1.00-1.30), never use of opium (1.85, 1.19-2.86), lower physical activity (1.45, 1.20-1.72), being normal weight in 15-year body pictogram and being overweight (1.87, 1.59-2.20) or obese (3.20, 2.74-3.72) in 30-year body pictogram when considering those with normal weight or MHO.

Conclusion

Potentially modifiable factors including physical activity should be more emphasized. Furthermore, our study issued that it would be more reasonable that the prevention of unhealthy obesity be initiated before the development of MHO, where there are more protective factors and they could be more effective.

Association of legumes and nuts consumption with metabolic health status in Iranian overweight and obese adolescents

Limited data are available on the association of legumes and nuts consumption with health status in pediatrics. So, we assessed the relation of legumes and nuts intake with metabolic health status in Iranian adolescents. A random sample of overweight/obese adolescents aged 12 to 18 years was included in this cross-sectional study. Dietary intakes were gathered using a validated 147-item food frequency questionnaire (FFQ). We measured metabolic indices including blood pressure, lipid profile, glycemic and anthropometrics indices. Two strategies were used for classification of adolescents to metabolically healthy obese (MHO) or unhealthy obese (MUO): International Diabetes Federation (IDF) and combination of IDF with Homeostasis Model Assessment Insulin Resistance (HOMA-IR). Information on 203 overweight/obese adolescents (50.2% girls and 49.8% boys) with an average age of 13.98 (± 1.61) years and a mean weight of 73.48 (± 11.60) kg/m² was evaluated. Based on the IDF and IDF/HOMA-IR definition, higher consumption of legumes and nuts consumption was related to a 66% and 61% decreased odds of MUO in crude model (OR = 0.34, 95%CI 0.17-0.69), (OR = 0.39, 95%CI 0.19-0.80); but in fully-adjusted model, these relations disappeared. After adjustment for potential cofounders, an inverse association was found between legumes and nuts consumption and odds of hyperglycemia (OR = 0.35, 95%CI 0.16-0.78). Moreover, although inverse significant associations were found between legumes and nuts consumption and odds of MUO in girls and overweight subjects in crude models, these associations disappeared after adjustment for all confounders. After taking potential confounders into account, no significant association was found between consumption of legumes and nuts and MUO in Iranian adolescents. The findings should be affirmed by further prospective studies.

Contribution of 20-year body mass index and waist circumference history to poor cardiometabolic health in overweight/obese and normal weight adults: A cohort study

BACKGROUND AND AIMS

We investigated the associations of 20-year body mass index (BMI) and waist circumference (WC) histories with risk of being 1) metabolically unhealthy overweight/obese (MUOO) vs metabolically healthy overweight/obese (MHOO) and 2) metabolically unhealthy normal weight (MUNW) vs metabolically healthy normal weight (MHNW).

METHODS AND RESULTS

Participants comprised 3018 adults (2280 males; 738 females) with BMI and WC measured, every ~5 years, in 1991-1994, 1997-1999, 2002-2004, 2007-2009, and 2012-2013. Mean age in 2012-2013 was 69.3 years, with a range of 59.7-82.2 years. Duration was defined as the number of times a person was overweight/obese (or centrally obese) across the 5 visits, severity as each person's mean BMI (or WC), and variability as the within-person standard deviation of BMI (or WC). At the 2013-2013 visit, participants were categorised based on their weight (overweight/obese or normal weight; body mass index (BMI) ≥25 kg/m2) and health status (healthy or unhealthy; two or more of hypertension, low high-density lipoprotein cholesterol, high triglycerides, high glucose, and high homeostatic model assessment of insulin resistance). Logistic regression was used to estimate associations with the risk of being MUNW (reference MHNW) and MUOO (reference MHOO) at the last visit. BMI and WC severity were each related to increased risk of being unhealthy, with estimates being stronger among normal weight than overweight/obese adults. The estimates for variability exposures became null upon adjustment for severity. Individuals who were overweight/obese at all 5 time points had a 1.60 (0.96-2.67) times higher risk of being MUOO than MHOO compared to those who were only overweight/obese at one (i.e., the last) time point. The corresponding estimate for central obesity was 4.20 (2.88-6.12). Greater duration was also related to higher risk of MUNW than MHNW.

CONCLUSION

Being overweight/obese yet healthy seems to be partially attributable to lower exposure to adiposity across 20 years of adulthood. The results highlight the importance of maintaining optimum and stable BMI and WC, both in adults who become and do not become overweight/obese.

Metabolically Healthy Obesity-Heterogeneity in Definitions and Unconventional Factors

The concept of heterogeneity among obese individuals in their risk for developing metabolic dysfunction and associated complications has been recognized for decades. At the origin of the heterogeneity idea is the acknowledgement that individuals with central obesity are more prone to developing type 2 diabetes and cardiovascular disease than those with peripheral obesity. There have been attempts to categorize subjects according to their metabolic health and degree of obesity giving rise to different obese and non-obese phenotypes that include metabolically unhealthy normal-weight (MUHNW), metabolically healthy obese (MHO), and metabolically unhealthy obese (MUO). Individuals belonging to the MHO phenotype are obese according to their body mass index although exhibiting fewer or none metabolic anomalies such as type 2 diabetes, dyslipidemia, hypertension, and/or unfavorable inflammatory and fribinolytic profiles. However, some authors claim that MHO is only transient in nature. Additionally, the phenotype categorization is controversial as it lacks standardized definitions possibly blurring the distinction between obesity phenotypes and confounding the associations with health outcomes. To add to the discussion, the factors underlying the origin or protection from metabolic deterioration and cardiometabolic risk for these subclasses are being intensely investigated and several hypotheses have been put forward. In the present review, we compare the different definitions of obesity phenotypes and present several possible factors underlying them (adipose tissue distribution and cellularity, contaminant accumulation on the adipose tissue, dysbiosis and metabolic endotoxemia imposing on to the endocannabinoid tone and inflammasome, and nutrient intake and dietary patterns) having inflammatory activation at the center.

Physical Activity and Risk of Metabolic Phenotypes of Obesity: A Prospective Taiwanese Cohort Study in More Than 200,000 Adults

OBJECTIVE

To examine the association between physical activity (PA) and the risk for metabolically unhealthy obesity (MUO) or metabolically healthy obesity (MHO) in Asian adults.

PATIENTS AND METHODS

Data were obtained from 205,745 healthy individuals 18 years or older. Individuals were classified as inactive, lower or upper insufficiently active, active, and high active. Metabolically unhealthy was defined as having 1 or more of the metabolic syndrome criteria, excluding the abdominal obesity criterion.

RESULTS

The percentages of metabolically healthy normal-weight (MHNW), metabolically healthy overweight (MHOW), MHO, and MUO in our cohort were 30.8% (63,408 of 205,745), 5.8% (12,002 of 205,745), 4.1% (8329 of 205,745), and 20.7% (42,564 of 205,745), respectively. During a mean follow-up of 6 (range, 0.5-19) years, among 63,408 MHNW participants, 1890 (3.0%) and 1174 (1.9%) developed MUO and MHO, respectively. Among 12,002 MHOW participants, 3404 (28.4%) developed MUO and 2734 (22.8%) developed MHO. A total of 5506 of 8329 (66.1%) participants moved from MHO to MUO, and 5675 of 42,564 (13.3%) moved from MUO to MHO. Compared with being inactive, MHNW individuals who were active or high active showed lower risk for MUO. Among those with MHOW, being high active was associated with reduced risk for MUO and MHO. Although among MHO participants, PA was not associated with incident MUO, being active or high active was linked to a greater likelihood of moving from MUO to MHO.

CONCLUSION

PA may prevent the development of both MHO and MUO. PA also helps increase the transition from MUO to MHO, which may contribute to reduce the subsequent development of type 2 diabetes mellitus and major cardiovascular disease complications.

Body size trajectories and cardio-metabolic resilience to obesity

Individuals with obesity do not represent a single homogenous group in terms of cardio‐metabolic health prospects. The concept of metabolically healthy obesity is a crude way of capturing this heterogeneity and has resulted in a plethora of research linking to future outcomes to show that it is not a benign condition. By contrast, very few studies have looked back in time and modelled the life course processes and exposures that explain the heterogeneity in cardio‐metabolic health and morbidity and mortality risk among people with the same body mass index (BMI) (or waist circumference or percentage body fat). The aim of the Medical Research Council New Investigator Research Grant (MR/P023347/1) ‘Body size trajectories and cardio‐metabolic resilience to obesity in three United Kingdom birth cohorts’ is to reveal the body size trajectories, pubertal development patterns and other factors (e.g. early‐life adversity) that might attenuate the positive associations of adulthood obesity makers (e.g. BMI) with cardio‐metabolic disease risk factors and other outcomes, thereby providing some degree of protection against the adverse effects of obesity. This work builds on the Principle Investigator's previous research as part of the Cohort and Longitudinal Studies Enhancement Resources initiative and focuses on secondary data analysis in the nationally representative UK birth cohort studies (initiated in 1946, 1958 and 1970), which have life course body size and exposure data and a biomedical sweep in adulthood. The grant will provide novel evidence on the life course processes and exposures that lead to some people developing a cardio‐metabolic complication or disease or dying while other people with the same BMI do not. This paper details the grant's scientific rationale, research objectives and potential impact.