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A person's waist-to-height ratio (WtHR), occasionally written WtHR or called waist-to-stature ratio (WSR), is defined as their waist circumference divided by their height, both measured in the same units. It is used as a predictor of obesity-related cardiovascular disease. The WHtR is a measure of the distribution of body fat. Higher values of WHtR indicate higher risk of obesity-related cardiovascular diseases; it is correlated with abdominal obesity. [1]
More than twenty-five years ago, waist-to-height ratio (WHtR) was first suggested as a simple health risk assessment tool because it is a proxy for harmful central adiposity [2] and a boundary value of 0.5 was proposed to indicate increased risk. [3] [4] A WHtR of over 0.5 is critical and signifies an increased risk; a 2010 systematic review of published studies concluded that "WHtR may be advantageous because it avoids the need for age-, sex- and ethnic-specific boundary values". [5] In April 2022, the UK's National Institute for Health and Care Excellence (a government body) proposed new guidelines which suggested that all adults "ensure their waist size is less than half their height in order to help stave off serious health problems". [6] In September 2022, NICE formally adopted this guideline. [7]
According to World Health Organization guidance, the waist circumference is usually measured midway between the lower rib and the iliac crest. [8]
In April 2022, the UK's National Institute for Health and Care Excellence (a government body) proposed new guidelines which suggested that all adults "ensure their waist size is less than half their height in order to help stave off serious health problems". [9] In September 2022, NICE formally adopted this guideline. [10]
The October 2022 NICE guidelines have suggested boundary values for WHtR (defining the degree of central adiposity) as follows:
NICE say that these classifications can be used for people with a body mass index (BMI) of under 35, for both sexes and all ethnicities, including adults with high muscle mass. The health risks associated with higher levels of central adiposity include type 2 diabetes, hypertension and cardiovascular disease. NICE have proposed the same boundary values for children of 5 years and over. [11]
Boundary values were first suggested for WHtR in 1996 to reflect health implications and were portrayed on a simple chart of waist circumference against height. The boundary value of WHtR = 0.4 was suggested to indicate the start of the 'OK' range. The 0.5 boundary value was suggested to indicate the start of the 'Take Care' range, with the 0.6 boundary value indicated the start of the 'Take Action' range. [12]
The first boundary value for increased risk of WHtR 0.5 translates into the simple message "Keep your waist to less than half your height". [13] [14] The updated NICE guideline says "When talking to a person about their waist-to-height ratio, explain that they should try and keep their waist to half their height (so a waist-to height ratio of under 0.5)". [10]
A 2013 study identified critical threshold values according to age, with consequent significant reduction in life expectancy if exceeded. These are: WHtR greater than 0.5 for people under 40 years of age, 0.5 to 0.6 for people aged 40–50, and greater than 0.6 for people over 50 years of age. [15]
WHtR is a proxy for central (visceral or abdominal) adiposity: values of WHtR are significantly correlated with direct measures of central (visceral or abdominal) adiposity using techniques such as CT, MRI or DEXA. [4] [16] [17] [18]
WHtR is an indicator of 'early health risk': several systematic reviews and meta-analyses of data in adults of all ages, [19] [20] [21] [22] as well as in children and adolescents, [23] [24] have supported the superiority of WHtR over the use of BMI and waist circumference in predicting early health risk.
Cross-sectional studies in many different global populations have supported the premise that WHtR is a simple and effective anthropometric index to identify health risks in adults of all ages [20] [21] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] and in children and adolescents. [37] [38] [39] [40] [41] [42]
In a comprehensive narrative review, Yoo concluded that "additional use of WHtR with BMI or WC may be helpful because WHtR considers both height and central obesity. WHtR may be preferred because of its simplicity and because it does not require sex- and age-dependent cut-offs". [43]
Not only does WHtR have a close relationship with morbidity, it also has a clearer relationship with mortality than BMI. [44] [45] [46]
Many cross- sectional studies have shown that, even within the normal BMI range, many adults have WHtR which is above 0.5. [47] [48] [36] Many children show the same phenomenon. [49] [50] Risk factors for metabolic diseases [48] [51] and mortality are raised in these subjects. [52] [53] [54]
Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms (kg) and height in metres (m).
Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL).
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Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classified as obese when their body mass index (BMI)—a person's weight divided by the square of the person's height—is over 30 kg/m2; the range 25–30 kg/m2 is defined as overweight. Some East Asian countries use lower values to calculate obesity. Obesity is a major cause of disability and is correlated with various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis.
The waist is the part of the abdomen between the rib cage and hips. On people with slim bodies, the waist is the narrowest part of the torso.
The waist–hip ratio or waist-to-hip ratio (WHR) is the dimensionless ratio of the circumference of the waist to that of the hips. This is calculated as waist measurement divided by hip measurement. For example, a person with a 75 cm waist and 95 cm hips has WHR of about 0.79.
Sagittal abdominal diameter (SAD) is a measure of visceral obesity, the amount of fat in the gut region. SAD is the distance from the small of the back to the upper abdomen. SAD may be measured when standing or supine. SAD may be measured at any point from the narrowest point between the last rib and the iliac crests to the midpoint of the iliac crests.
Bariatric surgery is a medical term for surgical procedures used to manage obesity and obesity-related conditions. Long term weight loss with bariatric surgery may be achieved through alteration of gut hormones, physical reduction of stomach size, reduction of nutrient absorption, or a combination of these. Standard of care procedures include Roux en-Y bypass, sleeve gastrectomy, and biliopancreatic diversion with duodenal switch, from which weight loss is largely achieved by altering gut hormone levels responsible for hunger and satiety, leading to a new hormonal weight set point.
The obesity paradox is the finding in some studies of a lower mortality rate for overweight or obese people within certain subpopulations. The paradox has been observed in people with cardiovascular disease and cancer. Explanations for the paradox range from excess weight being protective to the statistical association being caused by methodological flaws such as confounding, detection bias, reverse causality, or selection bias.
Obesity classification is a ranking of obesity, the medical condition in which excess body fat has accumulated to the extent that it has an adverse effect on health. The World Health Organization (WHO) classifies obesity by body mass index (BMI). BMI is further evaluated in terms of fat distribution via the waist–hip ratio and total cardiovascular risk factors. In children, a healthy weight varies with sex and age, and obesity determination is in relation to a historical normal group.
Android fat distribution describes the distribution of human adipose tissue mainly around the trunk and upper body, in areas such as the abdomen, chest, shoulder and nape of the neck. This pattern may lead to an "apple”-shaped body or central obesity, and is more common in males than in females. Thus, the android fat distribution of men is about 48.6%, which is 10.3% higher than that of premenopausal women. In other cases, an ovoid shape forms, which does not differentiate between men and women. Generally, during early adulthood, females tend to have a more peripheral fat distribution such that their fat is evenly distributed over their body. However, it has been found that as females age, bear children and approach menopause, this distribution shifts towards the android pattern of fat distribution, resulting in a 42.1% increase in android body fat distribution in postmenopausal women. This could potentially provide evolutionary advantages such as lowering a woman's center of gravity making her more stable when carrying offspring.
The body adiposity index (BAI) is a method of estimating the amount of body fat in humans. The BAI is calculated without using body weight, unlike the body mass index (BMI). Instead, it uses the size of the hips compared to the person's height.
A number of lifestyle factors are known to be important to the development of type 2 diabetes including: obesity, physical activity, diet, stress, and urbanization. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women. A number of dietary factors such as sugar sweetened drinks and the type of fat in the diet appear to play a role.
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This article provides a global overview of the current trends and distribution of metabolic syndrome. Metabolic syndrome refers to a cluster of related risk factors for cardiovascular disease that includes abdominal obesity, diabetes, hypertension, and elevated cholesterol.
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