We all know smoking and bingeing on red meat and alcohol are bad for us. But how bad?

British statistician David Spiegelhalter, in a report published Monday in British Medical Journal, attempts to quantify which habits have a greater impact on life expectancy: Is drinking heavily worse than living a sedentary lifestyle?

To do this, he created a unit of measure called a "microlife," which corresponds to 30 minutes of life expectancy. Using other studies, he determined that for each day of heavy smoking, a person could be shaving about five hours off his life; someone who watches TV for two hours a day loses about 30 minutes for each day they take part in that activity.

"I'm taking lifelong habits and looking at how they affect people on average, convert it to a daily rate," Spiegelhalter says. "The whole idea is to make a comparison about healthy activities and bad activities. Crudely, drinking two cups of coffee will cancel out eating a burger."

Here's how different habits stack up, according to Spiegelhalter (estimates are based on various life expectancy studies and hours gained or lost are per day of exposure)

  • Smoking (15-24 cigarettes per day): -five hours
  • Alcohol: First drink, + 30 minutes; -15 minutes per subsequent drink per day
  • Sedentary behavior: -30 minutes per two hours of TV watching
  • Red meat: -30 minutes per three ounces of red meat consumed
  • Fruit & vegetables: five servings per day: +two hours
  • Exercise: +one hour for first 20 minutes, +30 minutes for every additional 40 minutes

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