Cut the Waist

Cut the Waist

Illustrative photo for 'Cut the Waist'
A modest reduction in waist circumference can have significant long term health benefits

Vascular screening:
Putting prevention first

Cardiovascular disease is the cause of almost half the deaths in the UK each year. The increasing prevalence of overweight and obesity is now fuelling an increase in cardiovascular disease and reduced life expectancy once again, despite significant advances in healthcare provision and treatment.

"Putting prevention first" is an initiative launched by the Department of Health that offers checks to people aged between 40 and 74 years of age to determine individual vascular risk. The "vascular checks" will identify those people who are at increased risk of cardiovascular disease, and help to support appropriate lifestyle change to reduce risk.

Preventing trouble ahead

The concept of vascular checks is very much in keeping with the ethos of "Cut the Waist", with a focus on "preventing trouble ahead".

Preventing trouble ahead

Over the last few decades, managing the increasing prevalence of obesity-related disease, such as cardiovascular disease and type 2 diabetes, has become a more and more daunting task. It is hoped that the "Putting prevention first" initiative, by offering appropriate interventions to at-risk individuals to reduce risk, will be the start of a focus towards "turning off the tap".

Mopping up the floor - an illustration of abdominal obesity
Adapted from BMJ 2001; 322: 716-720. Reproduced with permission from the BMJ Publishing Group.

This illustration depicts high blood pressure, type 2 diabetes and cholesterol problems, known as "dyslipidaemia", as risk factors for heart disease, driven by central fat accumulation. These risk factors are traditionally managed following diagnosis, with little emphasis on preventing development of these complications by supporting weight management and reduction in waist circumference.

Vascular screening and "putting prevention first" will hopefully highlight the importance of central fat accumulation and increased waist circumference. Interventions supporting at-risk patients to reduce waist circumference will help to manage or prevent obesity complications and help to "turn off the tap".

Why does central fat accumulation drive vascular disease?

Central fat accumulation and dyslipidaemia

The British Regional Heart Survey involved data from almost 5,000 men. Here we see that across large groups of individuals or populations, increasing BMI is associated with increasingly abnormal cholesterol profiles or dyslipidaemia, known to significantly increase the risk of coronary heart disease. As we shall see, it is the amount of visceral fat accumulation rather than BMI per se which drives this high risk cholesterol profile.

The British Regional Heart Survey data reflects the general trend towards an increase in visceral fat accumulation in male populations which starts at relatively low BMI values, just outside the normal BMI range of up to 35kg/m2.

British Regional Heart Survey data demonstrating atherogenic dyslipidaemia developing at BMI values just outside the normal range
British Regional Heart Survey data demonstrating atherogenic dyslipidaemia developing at BMI values just outside the normal range. Dyslipidaemia is associated with progressive accumulation of visceral fat.

Assessment of individual risk: vascular screening

Although with increasing BMI, there is a general tendency for an increase in visceral fat accumulation, there is considerable individual variation in the amount of visceral fat stored at any given BMI, depending upon ages, sex and ethnicity.

Here we can see that the expansion of visceral fat is a root cause of the "atherogenic dyslipidaemia" which leads to vascular disease.

Illustration of visceral fat associated dyslipidaemia”

Waist circumference measurement has advantages over BMI as it is a direct measure of central fat deposition and a more specific marker of visceral fat accumulation. It is therefore considered a more appropriate screening tool than BMI for individual patient assessment of vascular risk.

Measuring waist: measuring risk

Studies involving large numbers of people have confirmed that measurement of abdominal obesity and central fat accumulation is an important tool in assessing risk of heart disease and risk of death.

Abdominal obesity and risk of heart attack (INTERHEART)

The INTERHEART study was published in the Lancet in 20041. This multinational study took place in 52 countries and involved approximately 15,000 patients who had suffered a heart attack, and a similar number of "control patients" who were in hospital for other reasons.

The INTERHEART study gathered data to determine the nine most important risk factors which contributed over 90% of the risk of having a heart attack in the 15,152 patients studied.

This study confirmed that central fat accumulation or abdominal obesity contributed as much risk to developing heart disease as smoking (odds ratio 2.24 for abdominal obesity vs. 2.27 for smoking)

Abdominal obesity and heart disease: Interheart Study

Waist Circumference and all-cause mortality (EPIC)

The European Prospective Investigation into Cancer and Nutrition (EPIC) study has followed up almost 360,000 patients for approximately ten years2. Patients were categorised as being in one of five waist circumference ranges ("quintiles"). Those in the highest quintile for waist circumference were found to have double the risk of death from all causes compared to those within the lower waist circumference quintile over the ten year period of follow-up.

For every 5cm of waist circumference the study demonstrated a 17% increased relative risk of death for men and 13% for women that was independent of BMI category.

Cut the Waist and the Vascular Screening Programme

Universal vascular screening in the UK is anticipated to cost £250 million per year and likely to have a significant impact on NHS resources. It is clear that healthcare professionals need to understand the assessment of obesity and central fat accumulation if the programme is to have the greatest impact. Intuitively it would appear advantageous if the measurement used to screen vascular and diabetes risk lent itself to being incorporated into a public health message aimed at targeting at-risk individuals. In this respect, measurement of waist circumference has advantages over BMI as a tool for vascular screening.

Vascular screening: An opportunity to assess metabolic obesity

Presently the vascular screening programme does not involve a fasting blood test. Ideally waist circumference together with a fasting lipid profile to include triglycerides as well as the ratio of total cholesterol to HDL cholesterol (TC: HDL ratio), would appear to be an optimal way of screening those most at risk of dyslipidaemia associated with visceral fat accumulation and the "hypertriglyceridaemic waist phenotype". A random or fasting blood glucose, and an ALT would indicate propensity to glucose dysregulation and possible non-alcoholic steatohepatitis (NSAH), respectively and provide useful additional information regarding the impact of weight on health.

Once the degree of metabolic obesity is established, appropriate lifestyle change advice and support may be targeted to help those who are "screen positive" - those individuals identified by vascular screening as being most at risk of developing diabetes and vascular complications, through high-risk patterns of body fat distribution.

PDAY - Prevention begins at 40?

Should we consider screening people before 40 years of age?

Photograph showing 'fatty streaks' lining the right coronary artery in adolescent menThe Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study involved post-mortem results of almost 3,000 young people who died between 15 and 34 years of age in road traffic accidents. Even at this young age, abdominal obesity was associated with the earliest signs of coronary artery disease known as "fatty streaks", lining the right coronary artery in adolescent men. This study showed little evidence of early coronary artery disease in women, except those who were abdominally obese3.

The results of the PDAY study suggest that central fat accumulation is associated with very early signs of coronary heart disease, well before the age in which vascular checks are presently taking place. There may therefore be a case for prevention and performing vascular checks at an earlier age, particularly for young adults who demonstrate a tendency towards central fat accumulation. The propensity for early development of coronary heart disease in some people underscores the importance of early intervention via education and social marketing strategies such Change4Life.

Waist circumference cut off values

Waist circumference for adults above which risk increases are shown below. The exact level of risk depends upon ethnicity. Waist circumference cut off values can be applied to indicate broad risk categories in any population.

Studies on groups of people living in South Asia and people from South Asia living in the UK indicate that risk increases at a lower waist circumference cut off value than that observed in Caucasian populations.

Therefore the waist circumference cut off values to indicate increased risk is for values above 90cm in South Asian men and 80cm in South Asian women. These values correspond to lower BMI "action points" of 23kg/m2 and 27.5kg/m2 as suggested by the WHO to increased risk and high risk respectively in South Asian populations4.

Country/Ethnic Group Male Female
European (Europoid) 94cm 80cm
South Asians 90cm 80cm
Chinese 90cm 80cm
Japanese 90cm 80cm
Ethnic South & Central American Use South Asian recommendations Use South Asian recommendations
Sub-Saharan Africans Use European data Use European data
Eastern Mediterranean & Middle East (Arab) populations Use European data Use European data

References

1. Yusuf PS, Hawken S, Ounpuu S, Dans T et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study):Case-control study. Lancet 2004; 364:937-952

2. Pischon T, Boeing H, Hoffman K et al. General and abdominal adipocity and risk of death in Europe. New England Journal of Medicine 2008; 359:2105-20

3. McGill HC, Jr., McMahon CA, Herderick EE et al. Obesity accelerates the progression of coronary atherosclerosis in young men. Circulation 2002; 105: 2712-8

4. WHO expert consultation: Appropriate body mass index for Asian populations and its implications for policy and intervention strategies. Lancet 2004; 363: 157-63