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Waist-to-hip ratio better predictor of heart attack risk

11 November 2005 - written by Zosia Kmietowicz for Bupa's health information team

Measuring your waist-to-hip ratio is the best way to see if you're obese and at risk of having a heart attack, according to results of a new study published in The Lancet.1 If waist-to-hip ratio is used to define obesity - instead of the traditional body mass index (BMI) method - the number of people at risk of heart attack is three times what doctors currently estimate, say the researchers.

How was the study carried out?

More than 27,000 people from 52 countries took part in the study. 12,461 had already had a first heart attack. They were matched with people of the same sex and similar age who had not had a heart attack.

Participants were asked questions about their health, their economic status, their lifestyle and any family history of heart disease. Measurements were also taken of their weight, their height and their waist and hip circumferences.1

What did the study show?

The study showed that waist-to-hip ratio is much more accurate than BMI at predicting who will have a heart attack. The researchers found that BMIs in those participants who had suffered a heart attack before the study were only slightly higher than those who had not had a heart attack. In some populations - Arabs and people from southern Asia - BMI seemed to be of no value in predicting who would have a heart attack. By contrast, people who had had a heart attack had much higher waist-to-hip ratios than those who had not. This finding was valid in men and women, whatever their age and whatever part of the world they came from.

What did the researchers conclude?

The researchers concluded that waist-to-hip ratios are a much better way of deciding if someone is obese and at risk of having a heart attack than the traditional BMI method. They also found that:

  • a larger waist (which reflects the amount of abdominal fat) was harmful and increased a person's risk of heart attack
  • larger hips (which may indicate a person has more lower body muscle) are protective and reduce a person's risk of heart attack.

What is Body Mass Index (BMI)?

BMI is a measuring technique used to judge whether a person's weight is healthy. BMI uses weight and height. To work out your BMI, divide your weight in kilograms by your height in metres - and divide the answer by your height again.

Here is what the results mean:

  • BMI less than 18.5 means that you're underweight
  • BMI between 18.5 and 25 means that you're at a healthy weight
  • BMI between 25 and 30 means that you're overweight
  • BMI between 30 and 35 means that you're obese.

People are defined as being 'morbidly obese' if they have a BMI <40, or a BMI of 35-40 in the presence of other significant co-morbid conditions (eg diabetes, high blood pressure) that could be improved by weight loss.

What is waist-to-hip ratio?

This is another (and better) way of judging whether your weight is healthy. You can work out your waist-to-hip ratio by dividing the measurement of your waist by that of your hips. For men, a ratio should ideally not be over 0.90. For women, that figure is 0.85. The higher the number above these values, the greater your risk of heart disease.

How common is obesity?

About one quarter of men and women in England are obese.2 This is nearly double the number of people who were obese 10 years ago.2 Women are slightly more likely than men to be obese.

More children are also overweight than they used to be. In 2003, 4 in 10 children under 11 were either overweight or obese.3 In 1995, the figure was 3 in 10.3 Boys are slightly more likely than girls to be obese.3

However, these figures are based on calculations of BMI. If researchers used measures of waist-to-hip ratio the number of people classified as obese would be much higher, say the researchers.1

Obesity affects health in a number of ways. If you are obese you are at increased risk of:4

  • high blood pressure
  • diabetes
  • high cholesterol
  • having a heart attack
  • having a stroke
  • gallbladder disease
  • osteoarthritis
  • endometrial cancer.

In general, the more obese you are the greater your risk of getting health problems. For example, if you are moderately obese (i.e. your BMI is 32.5 or more) your chances of getting high blood pressure are twice that of someone who is not obese.4 If your BMI is more than 37.5 your risk is three times higher.4

There is also evidence that people who are obese have a shorter life expectancy than people who are of normal weight.4 Being obese can also lead to depression and fertility problems.5

Can losing weight help?

Yes. Losing weight can reduce the strain on the body - especially the major joints in the legs - making it easier to move. Exercising or moving more can improve muscle tone and help you feel better psychologically.5 Reducing some of the risk factors for heart disease through weight loss - such as blood pressure and cholesterol - should reduce the risk of heart disease.5

What's the best way to lose weight?

For most people, the best way to lose weight is to exercise more and to reduce calorie intake. Choose a diet that promotes gradual weight loss - between 0.5kg - 1kg (1-2 lbs) a week; otherwise you'll be losing water and muscle rather than fat. The key is to eat less of the wrong kinds of foods and more of the good kinds. Avoid fad diets, or exclusion diets, which are very restrictive and difficult to stick to. Instead, choose one that recommends a varied and balanced diet including all the major food groups. In general, your aim should be to reduce calorie intake by about 500-1000 calories a day. There are many useful books that can help you count your calories.

You should also try and exercise more. Aim to do 30 minutes of exercise a day - it should make you slightly warm and out of breath.

Bupa Information:

Further information

References

  1. Yusuf S, Hawken S, Ounpuu S, et al. Obesity and the risk of myocardial infraction in 27 000 participants form 52 countries: a case-control study. The Lancet 2005;366:1640-49.
  2. Health Survey for England 2003, Latest Trends. Department of Health, December 2004.
  3. Jotangia D, Moody A, Stamatakis E, Wardle H. Obesity among children under 11. National Centre for Social Research. April 2005.
  4. Thompson D, Edelsberg J, Colditz GA, et al. Lifetime health and economic consequences of obesity. Archives of Internal Medicine 1999;159:2177-2183.
  5. National Institute for Clinical Excellence. Guidance on the use of sibutramine for the treatment of obesity in adults. October 2001.
    www.nice.org.uk

All pages were accessed on 7 November 2005

 

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