The study found that the higher a woman's body mass index (BMI), the lower her chances were for survival.
Researchers also concluded that women who were lean at mid-life were the most likely to be in good mental and physical health after the age of 70.
A BMI between 19 and 25 is considered healthy, 25 to 30 is overweight and people with a BMI higher than 30 are considered medically obese.
The study accounted for mitigating factors including smoking and diet.
It is published in the medical journal BMJ.
The Associated Press contributed to this report.
- Link: Nurses' Health Study