People with certain metabolic risk factors who are obese are two and a half times as likely to develop heart disease as healthy people of normal weight. But those who are obese without these other risk factors still have a 28% increased risk of heart disease compared with healthy people of normal weight.
This suggests excess weight should be seen as an independent risk factor, challenging the idea that people can be “fat but fit”.
Metabolic risk factors for heart disease cluster together and in this large study the researchers defined “metabolically healthy” as not having; high blood pressure, raised blood sugar, high triglyceride (a type of fat), low HDL “good” cholesterol levels and increased waist measurements.
This large-scale observational research which tracked over 17,000 people in Europe for over 12 years gives us new insights into risk factors for heart disease. Findings suggest that prevention strategies should tackle all risk factors for people who are overweight or obese.
Why was this study needed?
It is estimated that over 30,000 people die in England because of obesity each year. In 2015, almost two-thirds of adults in England were overweight or obese. The cost of treating people who develop health problems due to obesity is around £6.1 billion a year.
Obese people risk developing medical problems which themselves cause heart disease, such as high blood pressure and type 2 diabetes.
Previously, it was thought that healthy obese people might not have an increased risk of heart disease unless they developed these metabolic risk factors.
In this study, the researchers looked at the effects of being overweight or obese and the cluster of metabolic risks on the chance of heart disease, both separately and in combination. Data came from a random sample of people taking part in the European Prospective Investigation into Cancer and Nutrition (EPIC) study.
What did this study do?
This prospective, observational study, EPIC-CVD, followed 17,640 adults from 10 European countries, including the UK. They were aged between 36 and 70 years with no history of a stroke or heart attack.
Participants completed questionnaires about diet, lifestyle, education and medical health. They were classified as metabolically unhealthy if they had three or more of the following: large waist circumference, high blood pressure, high blood glucose, high triglycerides and low HDL (good) cholesterol levels. Their BMI was also calculated at the start of the study. People were then followed up to see who developed coronary heart disease.
This was a large study with a long follow-up time of up to 12.2 years, and we can be confident in the results. Hazard ratios (HR) were appropriately adjusted for a range of factors that could have influenced the results; age, smoking, educational level, physical activity, a diet score, energy, and alcohol intake.
What did it find?
- Obese people with metabolic risk factors were two and a half times as likely to have heart disease compared with people of normal weight who were metabolically healthy (adjusted HR 2.54, 95% confidence interval [CI] 2.21 to 2.92).
- Metabolically unhealthy overweight people were more than twice as likely to develop heart disease as healthy people of normal weight (HR 2.33, 95% CI 1.97 to 2.76).
- Metabolically unhealthy people of normal weight had just over twice the risk of heart disease compared with those who were of normal weight and metabolically healthy (HR 2.15, 95% CI 1.79 to 2.57).
- Metabolically healthy obese people had a 28% increased risk of heart disease compared with people of normal weight who were metabolically healthy (HR 1.28, 95% CI 1.03 to 1.58).
- Metabolically healthy overweight people had a 26% increased risk of heart disease compared to healthy people of normal weight (HR 1.26, 95% CI 1.14 to 1.40).
What does current guidance say on this issue?
NICE 2014 guidelines recommend multicomponent lifestyle interventions as the treatment of choice for obesity. Weight management programmes should include behaviour change strategies. Drug treatments are recommended if the BMI is 35 or more. If the person also has other conditions such as type 2 diabetes, or if the BMI is 40 or more then surgical interventions can be considered.
NICE 2016 guidelines recommend healthcare professionals use the QRISK2 tool to assess cardiovascular risk. This is suitable for people up to age 84 years. Lifestyle modifications and taking statins and blood pressure lowering medication can then start as appropriate
What are the implications?
Having metabolic risk factors appears to be a greater risk than being overweight or obese alone. However, people who are obese and overweight and have metabolic risk factors are at the highest risk of heart disease.
These findings support current guidance recommending healthcare professionals address both obesity and metabolic risk factors as a priority. This would include advice about a healthy diet and exercise with referral to weight management services if more support is needed.
The current NHS health checks offer the chance to get checked for all these risks and the QRISK2 score, used in these, appropriately includes BMI as a continuous and independent risk factor.
Citation and Funding
Lassale C, Tzoulaki I, Moons KGM, et al. Separate and combined associations of obesity and metabolic health with coronary heart disease: a pan-European case-cohort analysis. Eur Heart J. 2017. [Epub ahead of print].
This project was funded by the European Union Framework 7 (HEALTH-F2-2012-279233), the European Research Council (268834), the UK Medical Research Council (G0800270 and MR/L003120/1), the British Heart Foundation (SP/09/002 and RG/08/014 and RG13/13/30194) and the UK National Institute for Health Research.
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Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre