The health risks associated with increased levels of body fat are commonly talked about, but where you store body fat may be of equal importance. This article highlights the numerous ways in which an elevated waist may be an indicator of your health status.
Why is body mass index (BMI) an insufficient indicator of health status?
BMI, a measure of weight over height, may be helpful for highlighting an individual at the more extreme ends of the weight spectrum. However, it does not consider body composition. Muscle mass is an important predictor of longevity and is positively associated with numerous health and performance measures: better health outcomes (Prado et al. 2018), reduced risk of chronic disease (Woolfe et al. 2006), increased bone density (Sutter et al. 2019), increased insulin sensitivity & metabolic health (Srikanthan et al. 2011) and maintaining a healthy weight. Utilising BMI alone does not consider muscle mass and therefore does not distinguish between those who are at a higher BMI due to body fat mass versus those who are at a higher BMI due to muscle mass.
Importantly, BMI does not consider body fat distribution. Fat can be classified according to its distribution: subcutaneous fat is found in the spaces between the skin and the muscles, whereas visceral fat is predominantly found around the organs in the abdominal area, such as the liver, intestines and kidneys. In healthy lean individuals, subcutaneous fat comprises approximately 80% of all fat tissue, providing a necessary and functional role to maintain health. However, excess subcutaneous fat can overspill and visceral fat may be generated. Visceral fat is dysfunctional and secretes harmful substances that contribute to poor metabolic health – from inflammation, to elevated levels of insulin and blood fat levels, to various other factors that may contribute to chronic health conditions such as type 2 diabetes and heart disease – Why what fat you have and where you store it matters may provide you with more information on body fat.
Regardless of being at a ‘healthy’ BMI, research indicates that if you have an increased waist circumference to height ratio (WHtR > 0.5), then you have increased health risks (Ashwell et al. 2016). As much as 25% of the UK population who are deemed to be at a ‘healthy’ weight using the BMI scale, are misclassified and may in fact need to be alerted to action their health (Ashwell et al. 2016). Whilst some research indicates that waist circumference (WC) coupled with BMI predicts health risk better than BMI alone, some findings indicate that WC alone is a stronger marker of health risk than BMI (Zhu et al. 2002).
Why waist circumference (WC) measurements?
WC is a simple method to indicate levels of fat stores around the abdomen which is strongly associated with visceral fat stores. Independent of BMI, WC is strongly associated with risk of death and cardiovascular disease associated death (Ross et al. 2020). Research indicates that when WC and BMI are considered together, for a given WC, the higher the BMI the lower the adverse health risk – this may be due to someone at a higher BMI being able to store subcutaneous fat in alternative places, such as around the hips and in the legs, reducing relative levels of visceral fat. An increased WC measurement may be associated with increased levels of visceral fat, associated with the production of harmful substances that have a deleterious effect on health (Philips et al. 2008).
As part of the body composition assessments, we offer in our clinic in London, we assess waist circumference, BMI and visceral fat amongst general fat mass, water levels, muscle mass and phase angle. This provides a more complete picture of body composition, allowing us to make more appropriate recommendations to our clients.
What waist circumference is considered borderline?
Above 102 cm for men and 88 cm for women is considered the “conventional risk limit”.
In clinic we work with a tighter range for males of <94cm and for females <80cm. This would be the range I would aim for with our clients to considerably lower associated health risk to waist circumference.
Health associations with elevated waist circumference & visceral fat
Life & health span
Waist circumference is an independent predictor of the development of health conditions and life span (Ross et al. 2020).
Inflammation
A chronic state of low-grade inflammation is associated with numerous chronic diseases – from type 2 diabetes to heart disease. Visceral fat stores around the intra-abdominal region is highly active and is associated with secreting lots of free fatty acids and large stores of harmful pro-inflammatory substances – namely cytokines (Alexopoulos et al. 2014). Cytokines may instigate a chronic low-grade inflammatory state where the immune system is impaired. Additionally, surrounding organs such as the liver, muscle and pancreas, become inflamed, as may the whole body. Inflammatory substances impact key metabolic processes, impairing the signalling of a key hormone named insulin, as well as blood sugar regulation (Chait et al. 2020).
Insulin resistance
Insulin is an important chemical messenger that plays a number of roles throughout the body. If insulin signalling is impaired, it may contribute to insulin resistance, impacting the processes involved in the generation of energy (metabolism) and subsequently be associated with health conditions. Visceral fat, associated with an increased WC, releases lots of broken-down fats (free fatty acids, FFAs) which may be associated with impaired insulin signalling and subsequent insulin resistance (Chait et al. 2020). Additionally visceral fat may have lower levels of substances that are negatively associated with insulin resistance (adiponectin and omentin) and increased levels of harmful substances positively associated with insulin resistance (resistin and cytokines) (Chait et al. 2020). The inflammation from visceral fat is likely to elevate levels of an inflammatory marker C-reactive protein (CRP), a prominent marker for insulin resistance and CVD).
Type 2 diabetes (T2DM)
Research indicates a strong association between increased WC and risk of developing T2DM (Borel et al. 2018, Feller et al. 2010). There is an even stronger association between waist circumference and T2DM risk at a lower BMI (Feller et al. 2010). Visceral fat is associated with lower levels of substances that may be helpful for blood sugar regulation (adiponectin and omentin) and increased levels of harmful substances associated with insulin resistance and the development of T2DM (resistin and cytokines) (Chait et al. 2020). The development of T2DM is strongly associated with a state of low-grade chronic inflammation that is associated with visceral fat.
Research indicates that individuals with a low or normal weight BMI (<25) with a large WC (men: >94 cm, women > 78.5 cm) have at least the same risk of developing T2DM as overweight individuals with a small WC (Feller et al. 2010). Additionally, WC may be especially helpful for indicating T2DM risk with particular ethnicities.
High blood pressure
Research indicates that individuals with an increased WC are at risk of experiencing high blood pressure (Jalal et al. 2009, Oviyanti et al. 2010, Sari et al. 2016, Borel et al. 2018). One contributing factor may be that visceral fat is associated with reduced levels of a substance which may be beneficial for blood pressure (adiponectin) (Wang et al. 2007) and an increase in harmful substances (leptin and pro inflammatory substances) which may negatively impact blood pressure (Simonds et al. 2014). Additionally, visceral fat, around the middle of the abdomen, may impact the release of FFA onto the liver, subsequently increasing blood pressure (Brookes et al. 2007).
High cholesterol levels
Research indicates that a larger WC is significantly associated with lower levels of beneficial cholesterol (high density lipoprotein) and higher levels of unhealthy cholesterol levels (low density lipoprotein) (Seidell et al. 2001) and blood fat levels (triglycerides) (Brenner et al. 2010). WC has been indicated to be a better predictor of blood fat and cholesterol levels than BMI, dependent upon ethnicity (Brenner et al. 2010). Increased levels of visceral fat are thought to increase the release of these substances into the bloodstream.
Non-alcoholic fatty liver disease (NAFLD)
NAFLD occurs when fat accumulates in the liver, causing inflammation, progressively leading to scarring and potentially impairing liver function. Visceral fat secretes a high number of harmful substances that can directly impact the liver, along with the proinflammatory substances (Chait et al. 2020). NAFLD is prevalent in approximately 16% of “normal” weight individuals (Milic et al. 2014). Research indicates that individuals who are lean and have NAFLD may in fact be at a much greater health risk (metabolic syndrome: T2DM, high blood pressure, CVD) than individuals who are classified as obese (Ren-Nan Fang et al. 2014). The research was used to highlight the need for WC measurements to be utilised in addition to BMI to help indicate metabolic complications caused by NAFLD.
Cardiovascular (CVD) risk
Numerous studies show a strong association between increased WC and increased CVD risk (Hong et al. 2012, Khera et al. 2018): regional distribution of body fat may be of more importance than excess fat in driving CVD risk (Despres et al. 1990, Bjorntop 1990). Intra-abdominal or visceral fat is associated with the release of harmful substances (proinflammatory) and an increase in cardiometabolic risk factors (inflammation, insulin resistance, increased risk of blood clotting, blood sugar dysregulation) contributing to an increase in CVD risk (Despres et al. 2012).
The International Atherosclerosis Society (IAS) and International Chair on Cardiometabolic Risk (ICCR) recommend that WC is adopted alongside BMI to assess, evaluate and manage cardiometabolic risk (Ross et al. 2020). When WC and BMI are considered together, for a given waist circumference, the higher the BMI the lower the CVD risk, which may be explained by increased accumulation of subcutaneous fat tissue in the lower body, protective against fat being stored around the heart, liver and muscle as visceral fat.
Obstructive sleep apnea syndrome
Otherwise known as the reduced airflow to the nose/mouth despite breathing efforts during sleep – the severity of which depends upon the degree of airway blocked (partial or fully). Research indicates that increased WC is associated with incidence of obstructive sleep apnea syndrome (Borel et al. 2018).
Join pain and lower back pain
An increased WC may be associated with increased vulnerability to lower back pain (Hussain et al. 2017, Brooks et al. 2016).
Can I improve this?
Yes! It is possible to reduce WC measurements through making changes within nutrition, physical activity and lifestyle. Research indicates that levels of inflammation can be significantly reduced through healthy weight loss, as can a reduction in many chronic diseases! Remember that you are not alone in this and gaining support along the journey can be helpful and empowering to meet your health goals enjoyably and effectively.
Key takeaways:
Weight and BMI may be insufficient indicators of health status: since they do not take into account body size, body composition and body fat distribution.
Waist circumference measurements may be strongly associated with levels of visceral fat: which secretes numerous harmful substances associated with increased health risks.
Elevated waist circumference measurements may be associated with a host of health implications: lower back pain, sleep apnea, inflammation, insulin resistance, dysregulated blood sugar management, type 2 diabetes, high blood pressure, high cholesterol, cardiovascular disease and non-alcohol fatty liver disease.
If you are interested in either preventing or treating an elevated WC, why not reach out to one of our qualified nutritionists or health coaches to find out more about how they may be able to support you on your journey?
You can also contact us if you are interested in performing a body composition assessment.
References
- Ross et al. (2020). Waist circumference as a vital sign in clinical practice: a consensus statement from the IAS and ICCR working group on visceral obesity.
- https://www.nature.com/articles/s41574-019-0310-7
- Ashwell et al (2016). Waist-to-height ratio as an indicator of ‘early health risk’: simpler and more predictive than using a ‘matrix’ based on BMI and waist circumference.
- Zhu et al. (2002). Waist circumference and obesity-associated risk factors among whites in the third National Health and Nutrition Examination Survey: clinical actions thresholds.
- Janssen et al. (2004). Waist circumference and not body mass index explains obesity-related health risks.
- https://academic.oup.com/ajcn/article/79/3/379/4690122?login=true
- Jalal et al. (2009).
- Oviyanti et al. 2010, Sari et al. 2016, Borel et al. 2018
- Wang et al. (2007). Adiponectin, cardiovascular function, and hypertension.
- https://www.ahajournals.org/doi/10.1161/HYPERTENSIONAHA.107.099424
- Simonds et al. (2014). Leptin mediates the increase in blood pressure associated with obesity.
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4259491/
- Brookes et al. (2007). Hypertension and fatty liver: guilty by association?
- https://www.nature.com/articles/1002148
- Feller et al. (2010). Body mass index, waist circumference and the risk of type 2 diabetes.
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2905837/
- Bran et al. (2008). Beneficial effects of subcutaneous fat transplantation on metabolism.
- Philips et al. (2008). The link between abdominal obesity and the metabolic syndrome.
- Hardy et al. (2012). What causes the insulin resistance underlying obesity?
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4038351/
- Hong et al. (2007). Metabolic syndrome, its preeminent clusters, incident coronary heart disease and all-cause mortality: results of a prospective analysis for the atherosclerosis risk in communities study.
- Khera et al. Accuracy of the pooled cohort equation to estimate atherosclerotic cardiovascular disease risk events by obesity class: a pooled assessment of five longitudinal cohort studies.
- Neeland et al. (2019). Visceral and ectopic fat, atherosclerosis, and cardiometabolic disease: a position statement.
- Despres et al. (1990). Regional distribution of body fat, plasma lipoproteins, and cardiovascular disease.
- Bjorntop (1990). “Portal” adipose tissue as a generator of risk factors for cardiovascular disease and diabetes.
- Despres et al. (2012). Body fat distribution and risk of cardiovascular disease.
- Alexopoulos et al. (2014). Visceral adipose tissue as a source of inflammation and promoter of atherosclerosis.
- Chait et al. (2020). Adipose tissue distribution, inflammation and its metabolic consequences, including diabetes and cardiovascular disease.
https://www.frontiersin.org/articles/10.3389/fcvm.2020.00022/full#h3 - Brenner et al. (2010). Comparison of body mass index and waist circumference as predictors of cardiometabolic health in a population of young Canadian adults.
- https://dmsjournal.biomedcentral.com/articles/10.1186/1758-5996-2-28
- Milic et al. (2014). Non-alcoholic fatty liver disease and obesity: biochemical, metabolic and clinical presentations.
- Ren-Nan Feng et al. (2014). Lean-non-alcoholic fatty liver disease increases risk for metabolic disorders in a normal weight Chinese population.
- Seidell et al. (2001). Waist and hip circumferences have independent and opposite effects on cardiovascular risk factors.
- https://academic.oup.com/ajcn/article/74/3/315/4739581
- Hussain et al. (2017). Fat mass and fat distribution are associated with low back pain intensity and disability: results from a cohort study.
- Brooks et al. (2016). Relative abdominal adiposity is associated with chronic low back pain: a preliminary explorative study.
