Weight gain affects healthy survival

There has been a steady increase in overweight and obese people worldwide. In 1976, 14.5% of American adults were overweight and obese. By 2003 – 2004, the percentage had increased by almost 5 times to 66.3%! Does weight gain during early adulthood and mid-life adversely impact upon one’s healthy survival beyond 70 years of age?

Researchers from the Harvard School of Public Health and University of Warwick tested their hypothesis that mid-life adiposity is associated with a reduced probability of maintaining an optimal health status among those who survive to 70 or older by using the data in the Nurses’ Health Study (BMJ 2009; 339: b3796). This study involved 121,700 female registered nurses aged 30 – 55 living in one of 11 US states who responded to a questionnaire about history of disease and demographic and lifestyle characteristics every 2 years from 1976 to 2000. Those nurses who survived to age 70 or older and as of age 70 were free from 11 major chronic diseases (cancer, diabetes, myocardial infarction (MI), congestive heart failure, coronary artery bypass surgery (CABG), stroke, kidney failure, chronic pulmonary disease, Parkinson’s disease, multiple sclerosis and amyotrophic lateral sclerosis), had no major cognitive function impairment, had no major physical functions limitation and had good mental health were termed “healthy survivors”. Nurses who survived to 70 but did not meet these 4 criteria are termed “usual survivors”. There were only 1686 (9.9%) “healthy survivors”.

At baseline, the healthy survivors were healthier, had received more education, a lower prevalence of cigarette smoking and somewhat better diet. In addition, when compared to usual survivors, they were less likely, at baseline, to have overall or central obesity and tended to gain less weight since age 18. The most common chronic diseases were cancer, coronary heart disease (MI and CABG) and diabetes. Increasing BMI at baseline was associated with reduced odds of healthy survival. Every one unit increase of BMI was associated with a 12% reduction of the odds of healthy survival. Compared to stable weight, weight gain since age 18 was significantly associated with reduced odds of healthy survival. For every 1 kg increase of weight since age 18, the odds of healthy survival were decreased by 4 – 6%. Even among non-smokers, compared to lean women (BMI 18.5 – 22.9), women with a BMI of 30 at baseline had 73% lower odds of healthy survival. Compared to women who maintained a stable weight, women who gained 20 kg had 84% lower odds of healthy survival. A higher BMI at 18 also adversely affected the chances of healthy survival. Relative to women with a BMI of 18.5 – 22.9 at age 18, those with a BMI of 23.0 – 24.9 had 15% lower odds of healthy survival and for those with a BMI ≥ 25, it was 33% lower.

The above study would imply that there is no safe period for becoming overweight in our lifetime. It behoves every one of us to stay vigilant about our weight and try to stay lean if we want to enjoy healthy survival at 70 and beyond.