Fidest – Agenzia giornalistica/press agency

Quotidiano di informazione – Anno 35 n°195

Study shows ‘obesity paradox’

Posted by fidest press agency su venerdì, 24 marzo 2023

Sophia Antipolis, New research has debunked the idea that there is an “obesity paradox”, whereby patients with heart failure who are overweight or obese are thought to be less likely to end up in hospital or die than people of normal weight.The “obesity paradox” relates to counter-intuitive findings suggesting that, although people are at greater risk of developing heart problems if they are overweight or obese, once a person has developed a heart condition, those with higher BMIs appeared to do better and were less likely to die than those of normal weight. Various explanations have been suggested, including the fact that once someone has developed heart problems, some extra fat is somehow protective against further health problems and death, especially as people who develop a severe and chronic illness often lose weight.The study published today is the first to look at different ways of measuring the size and proportions of patients, including BMI, but also anthropometric measurements such as waist-to-height ratio, waist circumference and waist-to-hip ratio, and adjusting the patient outcomes to take account of other factors that play a role in, or predict, these outcomes, such as levels of natriuretic peptides – hormones that are secreted in the blood when the heart is under pressure, as with heart failure.“Natriuretic peptides are the single most important prognostic variable in patients with heart failure. Normally, levels of natriuretic peptides rise in people with heart failure, but patients living with obesity have lower levels than those who are normal weight,” said Prof. McMurray.An “obesity-survival paradox” showed lower death rates for people with BMIs of 25 kg/m2 or more [4], but this was eliminated when the researchers adjusted the results to take account of all the factors that can affect outcomes, including levels of natriuretic peptides.First author of the study, Dr Jawad Butt, a research fellow from Copenhagen University Hospital—Rigshospitalet, Copenhagen (Denmark), who carried out the analyses, said: ” The paradox was far less evident when we looked at waist-to-height ratios, and it disappeared after adjustment for prognostic variables. After adjustment, both BMI and waist-to-height ratio showed that more body fat was associated with a greater risk of death or hospitalisation for heart failure, but this was more evident for waist-to-height ratio. When looking at waist-to-height ratio, we found the top 20% of people with the most fat had a 39% increased risk of being hospitalised for heart failure compared to people in the bottom 20% who had the least fat.” Prof. McMurray said: “Our study shows there is no ‘obesity survival paradox’ when we use better ways of measuring body fat. BMI does not take into account the location of fat in the body or its amount relative to muscle or the weight of the skeleton, which may differ according to sex, age and race. In heart failure specifically, retained fluid also contributes to body weight. It is indices that do not include weight, such as waist-to-height ratio, that have clarified the true relationship between body fat and patient outcomes in our study, showing that greater adiposity is actually associated with worse not better outcomes, including high rates of hospitalisation and worse health-related quality of life.“Obesity is not good and is bad in patients with heart failure and reduced ejection fraction. These observations raise the question as to whether weight loss might improve outcomes, and we need trials to test this. In the UK, the National Institute for Health and Care Excellence, NICE, now recommends that waist-to-height ratio instead of BMI is used for the general population, and we should support this for patients with heart failure too. Limitations of the study are that it can be more difficult to accurately measure body shapes, such as waist circumference, especially when the measurements are carried out by different people; there may be further unknown factors that could affect the results; the analysis was carried out on measurements and other data taken at the time participants joined the study and did not take account of any changes in weight or waist circumference during the follow-up period; there were no data on the cardiorespiratory fitness of the participants, which could have an effect on the link between anthropometric measurements and outcomes; and, finally, only 153 patients were underweight, with a BMI of less than 18.5 kg/m2 , and 171 patients with a waist-to-height ratio of less than 0.4 (0.5 is considered a healthy ratio), so the study’s findings cannot be extrapolated to patients with low BMIs or waist-to-hip ratio. (abstract by escardio)

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