Obesity may lead to an early death, but being a little overweight is associated with a lower risk of death, a new study review covering more than 3 million people has found.

Obesity can trigger off a variety of health complications like diabetes type 2, heart disease and inflammation. But, few recent studies have shown that people who have a large body mass index can actually survive many complications better than people who have normal body mass index.

Earlier study on "obesity paradox" revealed that being overweight or obese can actually save peoples' lives, especially if they've undergone a recent heart surgery. Research has also shown that people with high BMI have a higher chance of surviving after treatment for a heart disease.

"Estimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting," according to the study.

The study review included nearly 100 studies that were conducted on 3 million adults who were thin, overweight or obese.

The studies were conducted in United States, Canada, Europe, Australia, China, Taiwan, Japan, Brazil, India and Mexico.

Researchers found that obesity was associated with an increased risk (18 percent) of all-cause mortality while overweight was associated with lower risk (6 percent) of all-cause mortality, HealthDay reported.

"For people with a medical condition, survival is slightly better for people who are slightly heavier," the study author Katherine Flegal, a senior research scientist at the U.S. Centers for Disease Control and Prevention's National Center for Health Statistics, told Healthday.

Dr. Steven Heymsfield, co-author of an accompanying editorial said that the difference in mortality rate between overweight and normal weight people is very small. He added that body mass index may not be a good indicator of a person's overall health.

"Body mass index simply is a parameter; it doesn't take into consideration family history, it doesn't take into consideration smoking, fitness, cholesterol and other factors that should be considered beyond body mass index," Dr. William Cefalu, chief and professor of the section of endocrinology, diabetes and metabolism at Louisiana State University and co-author of the aforementioned editorial, told HealthDay.

The study is published in the Journal of the American Medical Association.