Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Nutrition and Food Sciences

First Advisor

Jean Harvey


Men and women have similar rates of obesity but the combined prevalence of overweight and obesity is higher among men. Men who are overweight are a high-risk group for many obesity-related chronic diseases, as they are more likely to carry excess weight in the abdomen, which is generally more harmful than weight stored in the lower body. Men are also less likely than women to perceive themselves as overweight, and thus are less likely to initiate weight loss through organized weight loss programs. On average, less than 27% of weight loss trial participants have been men.

Internet-based research is a low-cost, efficient way to produce novel hypotheses related to weight loss that may have previously escaped weight loss professionals. Additionally, incentives are an effective tool to motivate behavior change, and there is ample evidence to support the use of incentives to encourage many health-promoting behaviors, such as weight loss. The purpose our initial study was to facilitate intervention development by using crowdsourcing to detect unexpected beliefs and unpredicted barriers to male weight loss. The aim of our main study was to evaluate the impact of financial incentives to facilitate weight loss in men, delivered as part of a weight loss intervention.

Two separate studies were conducted. In the first project, participants were recruited to a crowdsourcing survey website which was used to generate hypotheses for behaviors related to overweight and obesity in men. Participants provided 21,846 responses to 193 questions. While several common themes seen in prior research were revealed such as previous health diagnoses and physical activity participation, other potential weight determinants such as dietary habits, sexual behaviors and self-perception were reported. Crowdsourcing in this context provides a mechanism to further investigate perceptions of weight and weight loss interventions in the male population that have not previously been documented. These insights will help guide future intervention design.

For the main project, a randomized trial compared the Gutbusters weight loss program (based on the REFIT program) alone with Gutbusters with escalating incentives for successful weight loss. The six-month intervention was conducted online with weekly in-person weight collections for the first 12 weeks. Gutbusters encouraged participants to make six 100-calorie changes to their daily diet, utilizing a variety of online lessons targeting specific eating behaviors. Measures included demographic information, height, weight, waist circumference, and body fat percentage.

Participants (N=102, 47. 0± 12. 3 yrs old, 32. 5 kg/m2, 80. 4% with at least two years of college) were randomized in a 1:1 ratio to Gutbusters or Gutbusters+Incentive. Significantly more Gutbusters+Incentive participants lost at least 5% of their baseline weight compared to the Gutbusters group at both 12 and 24 weeks. Similar to the aforementioned REFIT program, Gutbusters participants were able to achieve clinically significant weight loss. The Gutbusters+Incentive achieved greater rates of weight loss than the Gutbusters alone group, further supporting the value of incentives in promoting health behaviors.



Number of Pages

130 p.

Included in

Nutrition Commons