'Fat but Fit' is Myth; New UK Study Finds BMI>25 Ups MI Risk

A new study adds to the growing evidence that the possibility of being 'fat but fit' is nothing more than a myth, with results showing that carrying extra weight can increase the risk of a heart attack in otherwise healthy people.

Previous studies have suggested there is a subset of overweight people who appear to lack the adverse health effects of excess weight. They have been classed as 'metabolically healthy obese' in the medical community but as 'fat but fit' in the media. However, the current study, published in the European Heart Journal, has dispelled this myth.

Researchers have found that being overweight or obese increases a person's risk of coronary heart disease by up to 28% – even if they are metabolically healthy – when compared to those with a healthy body weight. Their findings suggest that even apparently "healthy" people should aim to maintain normal body weight that is within a healthy range.

Coronary heart disease (CHD) occurs when not enough blood gets to the heart due to clogged arteries, which can lead to heart attacks. According to the British Heart Foundation, CHD is responsible for nearly 70,000 deaths every year in the UK. There are 2.3 million people in the UK living with CHD.

Professor Metin Avkiran, associate medical director at the British Heart Foundation, which part-funded the research, points out in a statement: "Coronary heart disease – the cause of heart attacks and angina – is the UK's single biggest killer. But there are steps you can take to lower your risk."

European Follow-Up Study

In the largest study of its kind, a group led by researchers at Imperial College London (ICL) and the University of Cambridge have shown that otherwise healthy overweight people are still at increased risk of CHD when compared to people with a healthy weight. Scientists used data from the European Prospective Investigation into Cancer and Nutrition (EPIC) for their study.

They included more than half a million people from 10 European countries. After a follow-up period of more than 12 years, 7,637 people in the EPIC cohort experienced CHD events, including death from heart attack.

Categorizing the Participants

Using definitions from the World Health Organization (WHO), the researchers classified participants based on their body mass index (BMI), calculated as weight (kg) divided by the square of their height (m):

· Obese – a BMI of 30 or more

· Overweight – a BMI of 25 to less than 30

· Normal weight – a BMI between 18.5 and less than 25

A larger proportion of the control group – 63% – were women, with an average age of 53.6 years old and an average BMI of 26.1.

The participants were also categorised as 'unhealthy' if they had three or more of a number of metabolic markers, including:

· High blood pressure

· High blood glucose levels

· High triglyceride levels

· Low HDL cholesterol levels

· A waist size larger than 94cm in men or 80cm in women

The researchers adjusted the data to take into account lifestyle factors such as diet, exercise, smoking and socioeconomic status.

The Findings

When compared to the healthy weight group, the researchers found that those classed as unhealthy had more than double the risk of CHD. This was true of the unhealthy group whether they had a normal weight or were overweight or obese.

The analysis also revealed that within the apparently healthy group who did not have metabolic markers, there was a significant difference in outcomes for people depending on their weight. When compared to those who were of a healthy weight, people who were classified as healthy but overweight had an increased CHD risk of 26%, and those who were healthy but obese had an increased risk of 28%.

The researchers indicate that the excess weight itself may not be directly responsible for the increased risk of heart disease. They say increased blood pressure and high glucose levels, for example, could be indirect mechanisms. No follow-up measurements had been taken, so the researchers cannot show how the group's health status changed over time.

The researchers consider their findings as being important because countries such as the UK and USA currently do not provide weight loss guidelines for overweight people without traditional metabolic risk factors for CHD such as smoking, type 2 diabetes, high blood pressure and high blood cholesterol. They conclude that their study shows it is clear that there should be population-wide prevention and treatment of obesity and being overweight regardless of a person's initial metabolic status. Weight-loss strategies include making lifestyle changes that involve both diet and exercise and for obese patients can include surgery.

Reactions to the Study

Professor Nick Finder, honorary clinical professor, National Centre for Cardiovascular Prevention and Outcomes, UCL, says in a statement: "This is an important paper that directly refutes the concept that it is OK to be overweight or obese provided that you do not have any metabolic risk factors such as abnormal cholesterol, lipid, glucose or diabetes, or high blood pressure - the so-called metabolic syndrome.

"A strength of the study (apart from its size, rigour and 12-year follow-up) was that information on physical activity, smoking, diet and social status could be adjusted for."

In response to the study's conclusion, Professor Finder continues that it: "is fully justified and supports the ever-pressing need for governments, local authorities, public health bodies, and individuals to seriously address the issues leading to our current levels of overweight and obesity."

Dr Amitava Banerjee, senior clinical lecturer in Clinical Data Science and honorary consultant cardiologist, UCL, considers this to be a high-quality study, saying in a statement: "It is high quality because it recruited across European countries, was prospective and had good data on risk factors and the outcome (heart disease).

She continues: "There are two implications. First, this is strongly against the possibility of being obese and metabolically healthy. Second, heart disease risk increases with increasing weight but also increases as the risk factors for heart disease increase (e.g. blood pressure), even in normal weight individuals. The findings show that we need to view health holistically, including trying to maintain a healthy weight as one (among several) of the risk factors for heart disease."

Professor Avkiran, in commenting on the study, says: "This study provides robust evidence that there is no such thing as 'healthy obesity'. It conclusively shows that being obese increases a person's risk of developing heart disease, even if they are otherwise healthy.

"The take-home message here is that maintaining a healthy body weight is a key step towards maintaining a healthy heart."

SOURCES:

European Heart Journal: 'Separate and combined associations of obesity and metabolic health with coronary heart disease: a pan-European case-cohort analysis'

Imperial College London news release

British Heart Foundation