Nothing like some fructose-laden sangria to fuel a discussion about fat-loss.

A couple friends and I recently entered a joint weight loss competition with a few tweaks from the world of behavioral economics. The competition will last for 3 months, with awards and consequences assessed monthly. It was developed under the influence of Cuban food & sangria, hence the name “The Habana Competition”.

The goal is body recomposition — lower body fat percentages. We will be using DEXA scans for 4 months to determine the biggest improvement. To normalize for our differing initial body fat %, the winner each month will be determined based on the “Percent of Percent” (PoP) body fat loss. (You can hear the sangria talking in that term.)

“Percent of Percent” Body Fat Loss = ((End of Month Body Fat %) — (Initial Body Fat %)) / (Initial Body Fat %)

We chose this based on our hypothesis that the difficulty of losing fat is pretty similar for all 3 of us, given that we all:

Are in our 30s

Drink some alcohol & coffee

(Probably) all have initial body fat greater than 12% and less than 30%

Already exercise 2–5 times per week

and we estimate that body fat loss difficulty follows this totally made-up curve:

Corrections welcome

PoP also has the advantage that it does not incentivize pre-initial weigh-in binging. Binging before the first weigh-in will just increase the amount of fat loss required to win. Not advisable for winning the competition.

The Stakes 1: Competitive Incentives

This part is pretty standard and uses a loss aversion bias. Each contestant puts $50 each month into a betting pool. At the end of each month, the winner per “Percent of Percent” criteria will be awarded the pool money.

Tweak 1: Experiences are more valuable than cash. In the book Work Rules by Lazlo Bock of Google, Bock explains that Google has found rewarding Googlers with experience bonuses instead of cash leads to happier Googlers. Cash bonuses tend to be quickly forgotten and applied to useful but boring things like rent.

In our competition, the award money must be delivered in cash and spent within 24 hours of the win. No savings / checking accounts deposits allowed. This forces the winner to splurge and spend on a fun, memorable experience.

Tweak 2: The award money cannot be spent on other friends in the competition! While this may seem cruel, it is meant to ensure that motivation to win & lose fat remains high.

Thinking with backwards induction, if a contestant knows that the winner is likely to follow the Reciprocity bias and spread the award money equally with the losers (say, on a nice bottle of scotch or a tasty dinner), then the contestant is less likely to be motivated by winning. If they win, they might be expected to immediately re-distribute their winnings. If they lose, they expect their loss to come right back to them in the form of scotch or ropa vieja. In order to keep the benefits of Loss Aversion bias, we need to keep the winner’s behavior somewhat selfish.

The Stakes 2: Anti-Charity Incentives

Competitions can drive good behavior, but they have a huge potential downside. If one participant is clearly ahead, the other participants might lose motivation to keep trying. This happens in almost every health-related competition I’ve seen: walk-a-thons, weight loss competitions, etc. — most people quit because they get off to slow start and are so far behind.

We are introducing another level of Loss Aversion: The Anti-Charity. (Wording taken directly from Stickk).

In our agreement, each participant chooses an Anti-Charity and a goal. If the goal is not met, then the participant must donate $50 to their Anti-Charity.

A good Anti-Charity is one that makes you cringe. It causes literal disgust. When tempted by that donut, you think of your $50 going to that vile cause, and your appetite disappears. One of us is choosing a particularly revolting political candidate, another is choosing a loathsome financial institution. We would sooner flush the money down the toilet than direct it to those organizations.

A good Anti-Charity goal is NOT based on comparison with other participants, it’s based on comparison to yourself at the beginning of the competition. The point is to keep you motivated, even when your competitor has pulled off incredible results.

Participants:

Andres:

Intake Strategy: Cut out weekday booze, Calorie Awareness

Exercise Strategy: Walking the dog, Weights while listening to This American Life, Sailing

Chris:

Intake Strategy: Cut out weekday booze

Exercise Strategy: Orange Theory, Olympic Bar Workouts in home gym, Sailing

Nick:

Intake Strategy: Slow-Carb Diet, complete with Cheat Days, Chiptopia

Exercise Strategy: Basketball, Ultimate Frisbee, Biking to Work, Some weights

We will share the results in the coming months. Our initial DEXA scans are scheduled for July 17.

You’re invited to join as well. Just contact me if interested.

Huge thanks to the sources of inspiration: Thinking Fast and Slow, Nudge, Work Rules, 4 Hour Body, all of the Freakonomics series, Gamification Course on Coursera from UPenn, Game Theory on Coursera from Stanford, sangria