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Psychological and Behavioral Factors Identified That Predict Success of Lifestyle Interventions for Weight Loss

Key findings

  • This study explored associations between weight loss and early changes in psychological and behavioral factors in the Reach Ahead for Lifestyle and Health (REAL-Health)–Diabetes trial and the relative importance of those factors in predicting weight loss
  • Improvement in autonomous motivation was the most important predictor of weight loss during the first year of the two-year lifestyle intervention; it was the second most important predictor during the second year and at the one-year follow-up (month 36)
  • Average six-month improvement in depressive symptoms was the only psychological variable associated with weight loss at the end of the two-year intervention and one-year follow-up; it was the most important predictor of weight loss at one-year follow-up
  • Improvement in fat-related diet behavior was significantly associated with weight loss at the end of the two-year intervention and at the one-year follow-up

Psychological and behavioral factors have been shown to predict weight loss success with lifestyle interventions. Researchers at Massachusetts General Hospital recently examined which factors correlate with weight loss by conducting a secondary analysis of Reach Ahead for Lifestyle and Health (REAL-Health)–Diabetes, a real-world trial published in 2020 in the Journal of General Internal Medicine.

Janaki D. Vakharia, MD, director of the Diabetes Collaborative Care Clinic for Young Adults in the Diabetes Unit at Massachusetts General Hospital, Linda M. Delahanty, MS, RDN, LDN, director of nutrition and behavioral research in the Unit, Deborah J. Wexler, MD, MSc, chief of the Unit, and colleagues found lifestyle interventions for weight loss should focus on promoting autonomous motivation, flexible dietary self-regulation, and habituation of low-fat eating habits. They present the details in the Journal of the Academy of Nutrition and Dietetics.


REAL HEALTH–Diabetes, a randomized comparative effectiveness trial, had three arms: a lifestyle intervention for weight loss delivered in person, the same intervention delivered via telephone conference call and referral to a dietitian for medical nutrition therapy. This analysis included only the lifestyle intervention arms (in person, n=70; telehealth, n=72).

The trial was conducted between 2015 and 2020 at three community health centers and one diabetes clinic affiliated with Mass General. It comprised two years of intervention and one year of observational follow-up. The first six months were intensive: 14 weekly sessions were followed by five biweekly sessions.

Participants completed self-report questionnaires at baseline and intervals throughout the trial:

  • Problem Areas in Diabetes, which measures diabetes distress
  • Patient Health Questionnaire–8, which measures depressive symptoms
  • Treatment Self-Regulation Questionnaire, which measures autonomous (self-directed) motivation for lifestyle change
  • Exercise Self-Efficacy, which measures confidence in ability to exercise despite barriers
  • Diet Self-Efficacy, which measures confidence in ability to adopt healthy dietary behaviors
  • Social Support for Healthy Behaviors Scale, which measures encouragement from others
  • Fat-Related Diet Questionnaire, which measures adherence to healthy eating and low fat, low calorie diet behaviors
  • The dietary restraint subscale of the Dutch Eating Behavior Questionnaire, which measures dietary self-regulation

At the end of observation (month 36), percent weight loss was similar in the two lifestyle intervention groups: 4.4% in the in-person group and 5.3% in the telehealth group.

Associations of Patient-reported Variables With Weight Loss

Improvements over six months in the following variables were significantly associated with average percent weight loss:

  • Depressive symptoms—associated with greater weight loss at 12, 24, and 36 months
  • Fat-related diet behavior—at 12, 24, and 36 months
  • Autonomous motivation—at 12 and 24 months
  • Exercise self-efficacy—at 12 and 24 months
  • Diet self-efficacy—at 12 and 24 months
  • Dietary self-regulation—at 12 and 24 months
  • Diabetes-related distress—at 12 months

Social support for healthy behaviors was not significantly associated with weight loss at any time point.

Ranked Importance of the Variables

A random forest model ranked the importance of the six-month improvement in each variable in predicting weight loss:

  • At 24 months—Fat-related diet behavior was the most important, followed by autonomous motivation
  • At 36 months—Depressive symptoms were the most important, followed by autonomous motivation and fat-related diet behavior
  • Social support for healthy behaviors was the least important predictor of weight change at all three time points studied

Practical Recommendations for Clinicians

Advice about weight loss diets has recently shifted to focus on low carbohydrate intake, but there's consistent evidence from many studies that reducing dietary fat reduction is associated with lasting weight loss. This study supports that view and suggests lowering fat intake should continue to be a key focus of weight loss interventions.

Self-efficacy and autonomous motivation were not associated with weight loss at 36 months, but the improvements in those variables as a result of the intervention likely fostered the development and maintenance of low-fat diet behaviors. Registered dietitian nutritionists should teach and reinforce strategies to enhance self-efficacy around eating and activity; promote dietary self-regulation skills and habituation of low fat, low calorie eating behaviors; and keep a focus on intrinsic motivations for lifestyle change.

Increases in autonomous motivation, low-fat diet behaviors, and diet self-regulation were important during the active intervention period of skill building. However, clinically speaking, the lasting effects of establishing low-fat diet behaviors and the intrinsic rewards of fewer depressive symptoms (improved well-being, energy, and sleep) may be most valuable.

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