A group of healthy women showed increased cortisol levels after restricting their diets for three weeks; a separate group that monitored what they ate, but did not restrict their diets, experienced psychological stress. Most diets fail to create prolonged weight loss; a study found that 30 percent-64 percent of diet study participants gained back more weight than they lost. Diets may create stress that causes people to regain weight.
Dieting often results in psychological stress: monitoring daily caloric intake is a daily hassle; restricting one’s eating creates physical hunger, which can lead to nervousness and depression. Increased cortisol is a biochemical indicator of stress and accompanies weight gain.
This study investigated whether the monitoring and restricting aspects of dieting triggered elevated cortisol levels and psychological stress in a sample of women from UCLA and the University of Minnesota; data collection took place between September 2007 and January 2009. The authors recruited women who were already planning to diet before entering the study. Researchers randomly assigned participants to four groups: monitoring and restricting, restricting only, monitoring only, and control. Participants monitored their diets by completing a daily food diary; the restricting only group received pre-packaged meals and followed diet plans similar to Jenny Craig. Each trial lasted three weeks. All participants conducted their own saliva sampling to measure cortisol levels. Participants assessed their respective stress levels using a questionnaire.
- Restricting eating increased cortisol levels.
- Monitoring calorie intake increased perceived stress.
This study measured only whether dieting increased psychological and biochemical indicators of stress. Future investigations must examine how components of dieting and stress affect diet outcomes.