Healthy obesity

What is Healthy Obesity?

Although obesity is a major risk factor for cardiovascular disease and type 2 diabetes mellitus, about a third of obese individuals maintain healthy cardiometabolic profiles; this phenotype of healthy obesity may be linked to the location of adipose tissue and the metabolic characteristics of the fat. Some data also suggest that weight loss by healthy obese subjects may have an adverse impact on their favorable cardiometabolic profile.

Why is Healthy Obesity Worthwhile investigating?

Investigating why H.O can't be regarded as simply obesity e.g. treatment problems, some weight losing methods actually detrimental to H.O individual

Waste of money to treat all H.O individuals as simply obese?

The Cause of Healthy Obesity?

Proposed Mechanistic Determinants of the Healthy Obese Phenotype

Adipose tissue is an endocrine organ, releasing several inflammatory cytokines and expressing endocrine hormone receptors. Recent studies have suggested that the location of adipose tissue, the histological characteristics of adipose tissue and its metabolic activity may be more relevant than its total mass with regards to the healthy obese phenotype, and they may play a role in determining the cardiometabolic health of obese individuals (Wildman, 2009).

Adiponectin and Healthy Obesity

Adiponectin is a protein hormone which is secreted into the bloodstream from adipose tissue and modulates several metabolic processes, including fatty acid catabolism and glucose regulation. The level of adiponectin in the bloodstream is inversely correlated to the percentage of body fat in adults. It is associated with the suppression of metabolic processes that can lead to obesity, type 2 diabetes mellitus and NAFLD. Diabetics tend to have reduced levels of the hormone and levels of adiponectin are significantly increased with weight loss. Other metabolic effects of adiponectin action are: decreased gluconeogenesis and increased glucose uptake; lipid catabolism; protection from endothelial dysfunction; insulin sensitivity, and control of energy metabolism. Hypoadiponectinaemia, therefore, is an independent risk factor for metabolic syndrome and type 2 diabetes mellitus– two conditions associated with an unhealthy metabolic profile of obese individuals.

It has been found that there is an inverse relationship between body mass index (BMI) and concentrations of adiponectin in both humans and animals. However, recent studies have shown that in ob/ob mice - mutant mice that eat excessively and become obese - overexpression of the adiponectin gene in its adipose tissue increased plasma adiponectin concentrations, keeping them in a physiological range. This increase in adiponectin concentrations resulted in significant weight gain and reduced hyperglycaemia and amended metabolic abnormalities. These findings suggest a role of variable plasma adiponectin concentrations in the pathophysiology of the healthy obese phenotype. Data from one recent study shows that lack of suppression of adiponectin concentrations is independently associated with the metabolically healthy profile of certain obese individuals (Aguillar-Salinas et al, 2008).

One study with the aim to determine whether plasma adiponectin concentrations, which were similar to those of lean subjects, were associated with the healthy obese phenotype found that 20% of individuals with a BMI greater than 40kg/m2 had adiponectin concentrations on average higher than those of subjects with a normal BMI. Obese women and men with adiponectin concentrations higher than 12.49mg/litre and higher than 8.07mg/litre respectively, had an increased probability of being metabolically healthy. These results were proven to be significant in a logistic regression model after controlling the effect of insulin, age, and waist circumference. It was concluded from this study that there is a subgroup of obese individuals whose plasma adiponectin concentrations are similar to those of normal BMI subjects. It is thought this is a contributing factor to the metabolically healthy obese phenotype (Aguillar-Salinas et al, 2008).

Location of Adipose Tissue

Both central adiposity and ectopic fat (fat found in lean tissue) are thought to be associated with the role of fat location in healthy obesity. Some studies have found that healthy obese individuals have smaller waist circumferences or lower levels of abdominal visceral fat (VAT), compared to metabolically unhealthy individuals. This is not surprising as central visceral fat is drained into the portal circulation and contributes to insulin resistance and dyslipidaemia, two factors associated with cardiovascular risk and metabolic disturbances (Wildman, 2009). However, other studies produced data suggesting otherwise, and found that there were no differences in central obesity between healthy and at-risk obese individuals. High levels of subcutaneous adipose tissue (SAT) have been found in some studies to illicit protective effects against atherosclerosis, independent of levels of VAT. These findings suggest a possible role of SAT in the healthy obese phenotype. However, other studies have found that high levels of SAT and VAT contribute to elevated CVD risk factors, and no differences in SAT levels were found between healthy and at-risk obese individuals. This could be due to the suggested modifying effects of VAT on SAT's effects on metabolic profile; high levels on SAT have been shown to contribute to development of the metbolic syndrome when paired with loe VAT levels, but they seemed to be protective when paired with high levels of VAT (Wildman, 2009).

Victoria Catherine Pickard 19:57, 31 October 2011 (UTC)

Criticism of Current Data - Does the Healthy Obesity Phenotype Actually Exist?

Investigating whether or not H.O is a genuine phenotype or has this subgroup emerged as a result of methodological/ measurement issues? Are these people healthy and truely obese/ are they obese yet truely healthy?

Conflicting findings of meta-analyses from NEJM and American heart journal etc. the impact of adjusting for physical activity and the role of other parameters. eg. lack of any the metabolic syndrome criteria & no insulin resistance counts as healthy. non metabolic morbidity.

or if that overlaps too much with someone else's section I could cover:

the role of ethnicity: A higher proportion of black healthy obese? Possible underlying mechanism?

Losing weight can be harmful for the healthy obese: (Gaesser 1999)Tijmen van Slageren 18:38, 24 October 2011 (UTC)