Leanness combined with healthy lifestyle factors found to be most protective against early death

When a heavily-publicized 2013 JAMA study suggested that being overweight or mildly obese was associated with a reduced risk of death—confusion ensued. Could carrying a little extra weight really be protective? A review of the evidence revealed serious problems in the study’s methods, such as including participants who entered the study at a lower body mass index (BMI) due to underlying disease or history of smoking. A more recent study of over 10.6 million participants from around the world (which excluded smokers and individuals with existing chronic diseases) indicated that being overweight or obese is associated with a higher risk of dying prematurely, compared to those who are normal weight.

Beyond just BMI, a new study in the British Medical Journal finds that healthy lifestyle factors may play a larger role in promoting longevity than weight alone. (1) Again, the authors point out that certain people may be classified as “normal weight” but have unhealthy behaviors or disease conditions that promote a lower body weight, such as smoking, chronic diseases like cancer and heart disease, or frailty and other age-related weight loss as seen in the elderly. In comparison, someone who is overweight may appear healthier if they are free of disease and practice healthy lifestyle habits.

To address the combined effects of body weight and lifestyle factors, the authors analyzed more than 113,000 women and men who did not have cancer or heart disease at the start of the study, and evaluated not only BMI, but quality of diet, physical activity levels, smoking habits, and alcohol intake. The participants were followed for more than 32 years as part of the ongoing Nurses’ Health Study and Health Professionals’ Follow-up Study, and deaths were measured from all causes as well as specifically from cancer and heart disease.

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