Researchers from the University of Cambridge say lack of movement is far more dangerous than being overweight.
Based on their research, 676 thousand deaths each year occur due to lack of movement. The number of deaths due to obesity reached 337,000 cases.
Some experts say, walking for 20 minutes every day can reduce the risk of death.
The study also revealed that thin people who rarely exercised had a greater risk of developing health problems.
Meanwhile, people who are obese but regularly exercise have better health than those who never exercise.
This study was published in the American Journal of Clinical Nutrition which aims to determine the dangers of inactivity and obesity.
The researchers studied more than 334,000 respondents over 12 years.
Obesity vs rarely move
"The greatest risk [of premature death] was in those who were sedentary, and it was consistent in normal weight, overweight, and obesity," one of the researchers, Prof Ulf Ekelund told BBC News.
Prof Ekelund, who lives in Norway, does cross-country skiing and vigorous exercise for five hours each week.
However, he says brisk walking can change health.
"I think people need to take this into account in their daily lives"
"You can do 20 minutes of physical activity, like walking to work. It's better than watching television."
Diseases that result from inactivity and obesity are almost the same, namely heart disease.