Published in The Lancet, the review included 97 global studies and more than 1.8m people, and found that high blood pressure, serum cholesterol and blood glucose explained about half the increased risk of heart disease in overweight or obese people, and about three-quarters the increased stroke risk. High blood pressure was the biggest risk factor, accounting for about 31% of increased heart disease risk and about 65% of the increased stroke risk.
"Our results show that the harmful effects of being overweight or obese on heart disease and stroke partly occur by increasing blood pressure, serum cholesterol and blood glucose,” said senior author Goodarz Danaei, assistant professor of global health at the Harvard School of Public Health. “Therefore, if we control these risk factors, for example through better diagnosis and treatment of hypertension, we can prevent some of the harmful effects of being overweight or obese.”
The food and beverage industry has come under increasing pressure in recent years to help tackle obesity-related ill-health and has taken various approaches, including reformulation, more responsible marketing of less healthy products, portion control and advocating more balanced diets.
However, this latest study suggests that efforts to reduce disease risk may need to go beyond encouraging individuals to lose weight – although it did find that being overweight increased risk of heart disease and stroke compared to having a healthy weight. Obese individuals were at the greatest risk, the researchers found.
Professor Stephen Hill, chair of the Medical Research Council's Molecular and Cellular Medicine Board, which part-funded the work, said: "Large, long-term population studies like this one are a very powerful tool, allowing researchers to disentangle individual factors and understand how they each contribute to our risk of disease.
“It's interesting that, even when blood pressure, blood sugar and cholesterol are brought under control, obese individuals are still at a higher risk of heart attack and stroke. This suggests that other factors might be at play, which is likely to be of interest for future research into the consequences of obesity."
Source: The Lancet
“Metabolic mediators of the effects of body-mass index, overweight, and obesity on coronary heart disease and stroke: a pooled analysis of 97 prospective cohorts with 1·8 million participants”
Authors: Yuan Lu, Kaveh Hajifathalian, Majid Ezzati, Mark Woodward, Eric B Rimm, Goodarz Danaei.