2 formerly obese economists lost a combined 120 pounds in 18 months - here are the best tricks they used

• Christopher Payne and Rob Barnett are economists and the authors of "The Economists' Diet." They both were once obese.
• Payne and Barnett say the behaviors that affect weight can all be explained by the principles of economics.
• Those principles include: minimize decision-making, stick to a boring diet, and weigh yourself every day.

Rob Barnett calls it the "fateful conversation."

He'd just appeared on a video for Bloomberg, where he worked as an economist, discussing a recent news event.

Barnett asked a fellow Bloomberg economist, Christopher Payne: "Did you see my latest video?"

"Yeah, I saw it," Payne said. "Good job."

"Thanks," Barnett responded. "But f-k, man! I'm getting fat."

Payne didn't beat around the bush. "One could say that," he told Barnett. "One could also say that you are fat."

Barnett and Payne reproduce this conversation in their new book, "The Economist's Diet: The Surprising Formula for Losing Weight and Keeping It Off."

At the time of the fateful conversation, Barnett was severely obese. Payne could identify - at one point in his life, he'd been obese, too. Then he lost about 45 pounds in 18 months.

The authors say the exchange that followed helped them both realize that the behaviors that affect weight can all be explained by the principles of economics. Barnett eventually went on to lose 75 pounds, also in 18 months.

The book is an outgrowth of that original conversation: The authors teach readers how to approach weight loss the same way they did. I recently spoke with the authors over the phone about the weight-loss strategies I found most compelling. Here's what I learned: