The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do To Get More of It

by Kelly McGonigal

When Christakis and Fowler looked at participants’ weight over time, they saw what looked like a real epidemic. Obesity was infectious, spreading within families and from friend to friend. When a friend became obese, a person’s own future risk of becoming obese increased by 171 percent.