2 formerly obese economists who lost a combined 120 pounds in 18 months say 'meta-rules' were a key part of their success

Estrada Anton/Shutterstock

Lose weight without losing your mind.

• Christopher Payne and Rob Barnett are formerly obese economists and the authors of "The Economists' Diet."
• In explaining how to lose weight, hey recommend using "meta-rules," or guidelines that apply on all occasions, to lose weight.
• The idea is to minimize decision-making and save yourself some mental energy.

"Unless it's a special occasion, never have seconds."

"During the week, always have salad for lunch."

These seemingly stifling directives are examples of so-called "meta-rules," and they're designed to help you figure out how to lose weight without losing your mind.

Christopher Payne and Rob Barnett use the term, which they say they borrowed from behavioral economist Dan Ariely, in their book, "The Economists' Diet: The Surprising Formula for Losing Weight and Keeping It Off." Payne and Barnett are economists who worked together at Bloomberg; in their book, they guide readers in applying fundamental economic principles to the process of losing weight, the same way they did.

At different points in time, both Payne and Barnett were obese. Payne lost 45 pounds in 18 months, while Barnett lost 75 pounds in the same amount of time.

Meta-rules work for two reasons, the authors argue. The first reason: They eliminate the amount of choice you have in your daily diet. "The more times you present yourself with a choice, the more possibility there is to do something that you're trying not to do," Payne told me.

The second reason meta-rules work: They make life less exhausting while you're getting healthier. Payne said that if you're trying to lose weight, it's best to just not have whatever you're trying to avoid eating in your home. Otherwise, you'll have to make a decision every night about whether to indulge.

Barnett and Payne are hardly the first people to recognize the power in minimizing decision-making. For example, Max Levchin, a PayPal founder who's now the CEO of the online lending service Affirm, previously told Business Insider's Alyson Shontell about the importance of consistency in his fitness regimen.

"So long as your daily default is 'Be on the bike,' some days you'll miss because you're traveling or you're sick," he said. "But most of the time, you'll just get up, and get on a bike first thing in the morning, which is what I do."

The authors note, however, that meta-rules are not a panacea for anyone struggling with their weight.

In the book, they write: "The oath we make to ourselves doesn't protect us from having to make a decision; it just changes the decision from 'Shall I have dessert tonight? to 'Shall I break my oath tonight?' For sure, the latter holds more sway over us than the former, but it's not 100 percent foolproof."