MedicalResearch.com Interview with:
Dr Margaret Ashwell OBE, FAfN, RNutr (Public Health)
Ashwell, Hertfordshire, United Kingdom.
Visiting Research Fellow, Oxford Brookes University
MedicalResearch: What are the main findings from this study?
Dr. Ashwell: In this study, the authors explore the differences in CVD risk factors between overweight and non-overweight people (by BMI) according to their shape (waist-to-height ratio -WHtR) Data for their analysis was taken from the Health Survey for England 2009 (HSE). They found significant differences in levels of total cholesterol (TC) and glycated haemoglobin (HbA1c—a measure of blood sugar control used to diagnose diabetes).
Out of 2917 people aged 16 years and over, 346 classified as ‘normal’ by BMI, have WHtR exceeding 0.5 (12% of the total,sample, or 34% of normal weight people). These could be called non-overweight ‘apples’, who have a lot of fat around the waist but not a high BMI.
The researchers classified the HSE population into four groups (2×2) using standard boundary values of BMI (above or below 25kg/m2) and WHtR (above or below 0.5). The group with ‘low/normal BMI but high WHtR (non-overweight ‘apples’) had significantly higher mean TC than the group with high BMI but low WHtR (overweight ‘pears’—people with a higher than normal BMI but less fat around the waist): 5.73mmol/L vs. 4.98mmol/L. Similarly, HbA1c levels were higher among non-overweight ‘apples’ than among overweight ‘pears’ (5.62% vs. 5.33%). These differences were similar and also significant in both sexes.
MedicalResearch: Why do you say that piece so string can be used for primary screening?
Dr. Ashwell: Since a good boundary value for waist-to-height ratio is 0.5, you don’t even need a tape measure to screen those at risk. It can be done with a piece of string. Measure the height of child with string, fold it in half and see if it fits around his/her waist. If it doesn’t, that child should proceed to the next stage of screening.
MedicalResearch: Were you surprised by your study’s findings?
Dr. Ashwell: No because the science about the limitations of BMI and the superiority of WHtR has been growing in leaps and bounds recently.
MedicalResearch: Why do you think BMI is flawed?
Dr. Ashwell: It does not measure central obesity which is the type of obesity associated with the main health risks. And of course it measures muscle as well as fat
Why do you think your method using string is so effective?
It is simple and great for prevention especially in children and especially in developing countries where resources are scarce. Yet it is based on good science.
MedicalResearch: What is the background for this study? You have campaigned for more recognition of Waist to Height ratio (WHtR) for determination of cardiovascular risk. What first got you onto this theory?
Dr. Ashwell: Knowing that all the scientific evidence pointed to central obesity, not total obesity, being the main problem associated with health risks, I first suggested in 1994 that we needed a shape index to replace BMI. In 1996 we suggested that waist-to-height ratio could be such an index and all our work since then, and that of many others, has confirmed this suggestion to be sensible. Many other Shape Indices have been suggested but invariably waist-to-height ratio outperforms them as a risk indicator. It is certainly the simplest index.
MedicalResearch: What dangers is society facing if it continues to stick rigidly to BMI as its default method for screening risks related to obesity?
Dr. Ashwell: The ‘non- overweight weight’ apples (normal BMI but with waist-to-height ratio 0.5 or more) will not realise they are at risk and will not be recognised as needing care from health professionals.
MedicalResearch: Tell us how much developing countries can benefit from using something as basic as WHtR?
Dr. Ashwell: We have already been invited to India to help the academics produce a memorandum to their government to introduce our simple measure for screening Indian children. Since a good boundary value for waist-to-height ratio is 0.5, you don’t even need a tape measure to screen those at risk. It can be done with a piece of string. Measure the height of child with string, fold it in half and see if it fits around his/her waist. If it doesn’t, that child should proceed to the next stage of screening.
MedicalResearch: What are the next steps for your research in this area? What recommendations do you have for future research as a result of this study?
Dr. Ashwell: We would like to perform a systematic review on the comparisons of BMI and waist-to-height ratio as indicators of risk in children. There are sufficient individual studies published now to make this possible. Alternatively, we would like to hear that some other group have published this. We would also like to promulgate the message that WHtR is not only superior to BMI in first stage screening for the health risks of obesity but is also more efficient in practice and can be done by personnel with minimal training and resources.
MedicalResearch: What do you think is the biggest challenge the UK, and the rest of Europe, faces in terms of the obesity epidemic?
Dr. Ashwell: It must be prevention in children.
MedicalResearch: How would you frame the take-home message of the study?
Dr. Ashwell: “Keep your waist to less than half your height” if you want to stay healthy. This message is suitable for people ( children and adults) all over the world.
MedicalResearch: What should clinicians and patients take away from your report? What are the clinical implications of the findings?
Dr. Ashwell: Waist-to-height ratio should be measured and recorded as well as BMI. Valuable resources can then be focussed on those with the higher waist-to-height ratios
MedicalResearch: Does the risk increase at WHtR above 0.5?
Dr. Ashwell: Yes almost certainly it does as we know from other research . Above 0.6 and especially above 0.7,Mortality or years of life lost increases as well. We have not analysed subgroups yet in this dataset (need more data)
MedicalResearch: Is everyone with a WHtR > 0,5 at more risk of cardio-disease and diabetes?
Dr. Ashwell: This a population sample and is a statistical result, but it does mean that everyone with a WHtR of say 0.55 is at higher risk. Age is the most powerful predictor of all and dwarfs all other measures.
MedicalResearch: Does exercise help, even if you`re an “apple”?
Dr. Ashwell: Exercise always helps- especially if you are an apple! It can improve your metabolic profile and preserve your muscle mass
MedicalResearch: Do you have any financial disclosures?
This piece of research was self funded. Dr Margaret Ashwell has devised the Ashwell (R) Shape Chart which is distributed to health professional on a non profit making basis
Gibson S.1, Ashwell M.2,3
1Sig-Nurture Ltd, Surrey GU1 2TF, UK, 2Ashwell Associates, Ashwell, Herts SG7 5PZ, UK, 3Oxford Brookes University, Oxford OX3 0BP, UK
MedicalResearch.com Interview with:, & Dr Margaret Ashwell OBE, FAfN, RNutr (Public Health) (2015). To Stay Healthy: “Keep your waist to less than half your height”