Some recent studies have suggested that people who are overweight may live longer than their skinnier peers, named the “obesity paradox”. Now a huge review of hundreds of studies involving almost four million people has found that being overweight or obese does mean an earlier death, and this seems to be especially true for men.
The study analysis comes from the Global BMI Mortality Collaboration at the University of Cambridge. The researchers published their results July 13th in the journal The Lancet. By looking at a huge amount of data, the study authors were hoping to settle once and for all if extra weight means a shorter lifespan.
The current study pooled data from 239 different studies in 32 countries across Europe, North America, Asia, Australia, and New Zealand, since 1970. Almost four million participants were involved, and in all, there were about 1.6 million deaths. All the chosen participants had never smoked, were free of chronic disease at the start of their particular study, were between the ages of 20 and 90, and did not die within the first five years of their study. The researchers looked at the body mass index (BMI) of the participants, using this as an indication of the participants being underweight or overweight. The authors considered 20-25 BMI range to be normal.
When the study authors crunched the numbers, they discovered a relationship between BMI and risk of death. Those in the normal BMI range had the lowest death rates compared to people with either lower or higher BMI. Even mildly overweight participants had a higher risk of death than their normal BMI peers, and as BMI rose, so did the risk of death. The relationship between higher BMI and greater risk of death persisted at every age range, although the relationship was weaker for 70 to 89-year-olds. Men also tended to face a three times greater risk of premature death than women.
Of participants under the age of 70, the age considered the cutoff for premature death, men and women with a normal BMI faced a 19% and 11% risk of death, respectively. Moderately obese men and women, with a BMI between 30 and 35, faced a 29.5% and 14.6% risk of death. Not only was high BMI a higher risk for premature death, but the participants who had a lower than normal BMI faced a slightly increased risk. Overweight and obese study participants were more likely than those with normal BMI to die of heart disease, stroke, respiratory disease, and cancer.
The study did have limitations, such as using BMI as an indicator of weight. People with similar BMI can have drastically different weight distributions, and other studies had indicated abdominal fat to be associated with health risks more than fat in other locations on the body. That said, the study does challenge the notion that excess weight can have a protective effect on health, which some previous studies had asserted. When analyzing a large amount of data, there seems to be no support for the “obesity paradox.”
Body mass index, BMI, indicates the ratio of weight to height although it does not indicate body type and it does not distinguish between fat and muscle. The World Health Organization defines a BMI between 18.5 and 25 as normal, between 25 and 30 as overweight, 30 to 35 as moderately obese, and more than 40 as severely obese, although for the current study the researchers divided BMI into more categories. Estimates from the WHO place the number of adults worldwide who are overweight at 1.3 billion, with 600 million more considered obese. Obesity is a growing problem with increasingly poor diets and increasingly sedentary lifestyles.
Researchers have linked obesity to a greater risk of high blood pressure and high cholesterol, increasing the risk of heart disease and stroke. Obesity is also linked to type 2 diabetes, certain types of cancer, gallbladder disease, gout, osteoarthritis, sleep apnea, and asthma.