What behavioral economics teaches us about weight loss A Randomized Trial By: Kevin G. Volpp, MD, PhD; Leslie K. John, MS; Andrea B. Troxel, ScD et al (2008) 57 Participants, Philadelphia VA Medical Center
The Policy Problem
Obesity is a growing health emergency
Obesity rate rose from 13% (1960) to 31% (2004)
By 2004, 71% of U.S. adults overweight or obese
Unhealthy behaviors may account for up to 40% of premature mortality in the U.S.
Poor diet
sedentary lifestyle
Healthcare delivery failures account for only 10%
behavior and habits of society is the real lever here
Characteristics of Study Sample
The irrational Behavior
Only 10.5% of the control group met the 16-pound weight-loss goal. The gap between intention and action is where we see the irrational behavior and problem where people know what is best for themselves, but act in ways that don't reflect that.
People want to lose weight but they don't do it.
All participants rated weight control impatience 9.1-9.3/10
All rated their confidence in their ability to lose weight 8.3-8.5/10
The control group lost only 3.9 pounds on average without an incentive
The behavioral Biases
The brain is wired against long-term health...
Imperfect Self-Control:
Present Bias: eating feels good now, while health payoffs feel decades away
Self-control: choosing a burger in the moment, not salad, because one gives in to temptation
Habit: unhealthy eating and lifestyle become autopilot and routine
Nonstandard Preferences:
Loss aversion: Losses hurt 2x more than equivalent gains feel good
Framing: "you earn" vs "you missed."
Missing social norms and altruism
Imperfect Optimization:
Attention: people forget to give attention to long-term health goals
Overconfidence: they rated their confidence of completing the 16 weeks on average a 8.4/10 (no incentive), yet still failed.
And for you to wow your audience.
The Intervention
Two nudges that make the future feel more present... All Groups: Monthly clinic weigh-ins+free scale+1-hour dietitian consult at start Control: Weigh-ins only with no financial incentive Lottery Group: Daily chance to win $10 (1-in-5 odds) or $100 (1-in-100 odds), but only if on track with weight goal; $3/day expected value Deposit contract group (commitment device): Contribute $0.01-$3.00/day; government matches 1:1 +$3/day fixed; lose deposits if monthly goal is missed. Both groups: Daily text message feedback (reminders) on earnings and progress. Telling them what they missed if applied (regret framing) "fresh start" rule: monthly reset of trajectory for those who have lapsed.
Trial Diagram
Icons are always a good ally.
How does the study evaluate
Primary Outcome: the weight loss after 16 weeks on a clinical scale (which made it objective, avoiding self-reporting issues)
Intent to Treat Analysis: They counted dropouts as those who returned to baseline weight
Statistical test: F-tests that compared the incentive group to the control (significance cut off is low at 0.025, which accounts for the multiple comparisons)
Secondary Outcome: weight loss at 7-month follow up (testing if this method was sustainable)
IT WORKED!
This worked dramatically; however, the clock ran out. At 16 weeks:- Lottery: lost 13.1 pounds (p=0.02) - Deposit contract: lost 14.0 pounds (p-0.006) - Control: lost 3.9 pounds - 50% of both incentive groups hit the 16-pound loss goal vs 10.5% of the control group - Odds of hitting goal: 7.7x higher (deposit) and 9.4x higher (lottery) vs control
IT WORKED but...
At 7-month follow-up (3 months after incentives ended):- Weight difference between groups: no longer statistically significant - Lottery (p=.23) and Deposit (p=.61) - The incentive participants still weighed significantly less than their starting weight (.01 and .03, respectively); WHILE... control participants did not
Results
Results
We see the rebound in month 7. This shows the problem of sustainability.
Pro/Con with the study
Good Features of this study: - randomized control trial with pre-registered protocol - Objective outcome measure (clinic scale prevents flaws with self-reporting) - Intent-to-treat analysis (dropouts counted as returning to baseline weight) - Low dropout rate (there was high engagement)
Poor Features of this study: - N=57. It also needs multicenter replication - 94.7% male, which restricts generalizability to women - Self-selected volunteers mean the sample was more motivated than the average person to lose weight - Cannot isolate daily feedback from incentive effect - No long-term follow-up beyond the 7 months
The New Intervention
I want to make a study where:
Mornings set the mindset
We improve the daily routine structure to become a new healthy regular
Involving financial incentives
Ending with a graduation into a weight loss accountability group.
All done on an app with the appropriate features
Three phases
Phase 1: (weeks 1-16) Exactly as designed before, however, now we have a multiplier system anchored in a morning check-in. Money is the primary motivator, and the longer your streak, the more each day is worth. Every morning, participants complete a 60-second check-in, weighing themselves, logging their meal and exercise plans for the day, and seeing their current multiplier and how much today is worth. Days 1-7 $1/day Days 8-14 $2/day Day 15-30 $3/day Days 31-60 $5/day Days 61-112 $8/day end of phase 1
Three phases
Phase 2: (weeks 17-24) Then, we switch from money to something non-monetary. Now, each dollar that was earned back through phase 1 converts into something called "health capital," which is a score in the app that is only earned through sustained behavior. There is also a leaderboard, and the morning check-ins continue as usual Phase 3: (weeks 25+) A permanent peer accountability group of a maximum of 5 people following the same track and having similar scores. They meet weekly and this is the way to sustain the weight loss and create a social component aspect of accountability.
We now have a social component and sustainability that is designed to last more than 24 months
WHY Its Better
The compounding promotes a continuation of the good habit!
Works Cited: Volpp KG, John LK, Troxel AB, Norton L, Fassbender J, Loewenstein G. Financial Incentive–Based Approaches for Weight Loss: A Randomized Trial. JAMA. 2008;300(22):2631–2637. doi:10.1001/jama.2008.804
Financial Incentives for Weight Loss
Rachel Khoury
Created on March 24, 2026
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Transcript
By: Rachel Khoury
Gov 1759
Financial Incentives for Weight Loss
Pay $ to Lose Weight?
What behavioral economics teaches us about weight loss A Randomized Trial By: Kevin G. Volpp, MD, PhD; Leslie K. John, MS; Andrea B. Troxel, ScD et al (2008) 57 Participants, Philadelphia VA Medical Center
The Policy Problem
Obesity is a growing health emergency
Characteristics of Study Sample
The irrational Behavior
Only 10.5% of the control group met the 16-pound weight-loss goal. The gap between intention and action is where we see the irrational behavior and problem where people know what is best for themselves, but act in ways that don't reflect that.
People want to lose weight but they don't do it.- All participants rated weight control impatience 9.1-9.3/10
- All rated their confidence in their ability to lose weight 8.3-8.5/10
- The control group lost only 3.9 pounds on average without an incentive
The behavioral Biases
The brain is wired against long-term health...
Imperfect Self-Control:- Attention: people forget to give attention to long-term health goals
- Overconfidence: they rated their confidence of completing the 16 weeks on average a 8.4/10 (no incentive), yet still failed.
- Present Bias: eating feels good now, while health payoffs feel decades away
- Self-control: choosing a burger in the moment, not salad, because one gives in to temptation
- Habit: unhealthy eating and lifestyle become autopilot and routine
Nonstandard Preferences:- Loss aversion: Losses hurt 2x more than equivalent gains feel good
- Framing: "you earn" vs "you missed."
- Missing social norms and altruism
Imperfect Optimization:And for you to wow your audience.
The Intervention
Two nudges that make the future feel more present... All Groups: Monthly clinic weigh-ins+free scale+1-hour dietitian consult at start Control: Weigh-ins only with no financial incentive Lottery Group: Daily chance to win $10 (1-in-5 odds) or $100 (1-in-100 odds), but only if on track with weight goal; $3/day expected value Deposit contract group (commitment device): Contribute $0.01-$3.00/day; government matches 1:1 +$3/day fixed; lose deposits if monthly goal is missed. Both groups: Daily text message feedback (reminders) on earnings and progress. Telling them what they missed if applied (regret framing) "fresh start" rule: monthly reset of trajectory for those who have lapsed.
Trial Diagram
Icons are always a good ally.
How does the study evaluate
IT WORKED!
This worked dramatically; however, the clock ran out. At 16 weeks:- Lottery: lost 13.1 pounds (p=0.02) - Deposit contract: lost 14.0 pounds (p-0.006) - Control: lost 3.9 pounds - 50% of both incentive groups hit the 16-pound loss goal vs 10.5% of the control group - Odds of hitting goal: 7.7x higher (deposit) and 9.4x higher (lottery) vs control
IT WORKED but...
At 7-month follow-up (3 months after incentives ended):- Weight difference between groups: no longer statistically significant - Lottery (p=.23) and Deposit (p=.61) - The incentive participants still weighed significantly less than their starting weight (.01 and .03, respectively); WHILE... control participants did not
Results
Results
We see the rebound in month 7. This shows the problem of sustainability.
Pro/Con with the study
Good Features of this study: - randomized control trial with pre-registered protocol - Objective outcome measure (clinic scale prevents flaws with self-reporting) - Intent-to-treat analysis (dropouts counted as returning to baseline weight) - Low dropout rate (there was high engagement)
Poor Features of this study: - N=57. It also needs multicenter replication - 94.7% male, which restricts generalizability to women - Self-selected volunteers mean the sample was more motivated than the average person to lose weight - Cannot isolate daily feedback from incentive effect - No long-term follow-up beyond the 7 months
The New Intervention
I want to make a study where:
- Mornings set the mindset
- We improve the daily routine structure to become a new healthy regular
- Involving financial incentives
- Ending with a graduation into a weight loss accountability group.
All done on an app with the appropriate featuresThree phases
Phase 1: (weeks 1-16) Exactly as designed before, however, now we have a multiplier system anchored in a morning check-in. Money is the primary motivator, and the longer your streak, the more each day is worth. Every morning, participants complete a 60-second check-in, weighing themselves, logging their meal and exercise plans for the day, and seeing their current multiplier and how much today is worth. Days 1-7 $1/day Days 8-14 $2/day Day 15-30 $3/day Days 31-60 $5/day Days 61-112 $8/day end of phase 1
Three phases
Phase 2: (weeks 17-24) Then, we switch from money to something non-monetary. Now, each dollar that was earned back through phase 1 converts into something called "health capital," which is a score in the app that is only earned through sustained behavior. There is also a leaderboard, and the morning check-ins continue as usual Phase 3: (weeks 25+) A permanent peer accountability group of a maximum of 5 people following the same track and having similar scores. They meet weekly and this is the way to sustain the weight loss and create a social component aspect of accountability.
We now have a social component and sustainability that is designed to last more than 24 months
WHY Its Better
The compounding promotes a continuation of the good habit!
Works Cited: Volpp KG, John LK, Troxel AB, Norton L, Fassbender J, Loewenstein G. Financial Incentive–Based Approaches for Weight Loss: A Randomized Trial. JAMA. 2008;300(22):2631–2637. doi:10.1001/jama.2008.804
Thank you!