Intermittent Fasting Versus Daily Caloric Restriction for Weight Loss
Condition: Obesity
MeSH terms: Obesity; Weight Loss
Study type: Interventional

Summary: 
      The primary aim of this study is to is to determine if intermittent fasting (IMF) is an
      effective dietary strategy for treatment of obesity. A 1 year randomized trial will be used
      to compare weight loss generated by IMF versus Daily Caloric Restriction (DCR). The targeted
      weekly energy deficit is designed to be similar (~30%) and a comprehensive behavioral support
      program will be provided to both groups. The primary outcome is weight change at the end of
      the 1 year intervention; follow up measures will also be obtained 6 months after completing
      the intervention. This study will provide robust data regarding weight loss effectiveness of
      IMF and will further our understanding of the impact of IMF on energy balance.
    

Detailed description: 
      Restricting daily calorie intake is the primary dietary strategy currently used to treat
      obesity. However, this approach is not effective for all individuals. Further, adherence to
      daily caloric restriction (DCR) typically decreases over time and many individuals who lose
      weight with this strategy will regain. Thus, novel dietary interventions are needed to
      provide a broader range of treatment options. The objective of this proposal is to determine
      if intermittent fasting (IMF) is an effective dietary strategy for treatment of obesity. IMF
      is an alternative method of reducing energy intake (EI) which has gained lay popularity in
      recent years as a strategy for weight loss. Short-term studies suggest IMF produces 3-8%
      weight loss in individuals with overweight and obesity. However, few studies have compared
      IMF to DCR and no studies have evaluated whether IMF is an effective long-term (≥1 year)
      weight loss strategy. Data from an 8-week pilot study comparing IMF to DCR suggests IMF is
      safe, tolerable, and produces similar short-term weight loss. After 6 months of unsupervised
      follow-up, changes in body composition tended to be more favorable with IMF and almost twice
      as many IMF participants maintained a ≥5 kg weight loss. Thus, IMF may be a more effective
      dietary strategy for sustaining weight loss than DCR. However, longer-term data are needed
      and little is known about adherence to IMF or the impact of IMF on energy expenditure (EE).
      Short-term studies suggest adherence to IMF may be superior to DCR, however, energy intake
      (EI) was based on self-report which may have significant limitations. Pilot data suggests
      resting energy expenditure (REE) was preserved during IMF-induced weight loss, which could
      decrease risk for weight regain. However, the impact of IMF on other components of EE
      including physical activity (PA) is largely unexamined. The study design is a pragmatic
      randomized trial to compare weight loss generated by IMF vs DCR. The targeted weekly energy
      deficit will be equivalent: DCR will be prescribed a ~30% daily energy restriction and IMF
      will be prescribed a modified fast (~80% energy restriction) on 3 non-consecutive days per
      week. The hypothesis is that a weight loss program based on IMF as the primary dietary
      strategy will result in greater weight loss at 1 year compared to a program based on
      traditional DCR. The approach is innovative as the targeted energy deficit will be matched
      between groups and EI will be assessed objectively (using doubly-labeled water) to provide an
      accurate comparison of adherence. In addition, both intervention groups will receive
      guidelines-based behavioral support to compare IMF to the current standard of care (DCR) in a
      more robust fashion. This study is significant as it could identify an effective alternative
      dietary strategy to help more people achieve and sustain weight loss.
    

Intervention name(s): Daily Caloric Restriction (DCR); Intermittent Fasting (IMF)
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Participants in this group will be given a calorie goal designed to produce a 34.3% energy deficit from estimated baseline weight maintenance energy requirements. Participants in this group will also receive a 12 month comprehensive group-based behavioral weight loss program and will be instructed in specific strategies to support DCR. Randomized groups will meet separately. Participants in this group will also be asked to increase moderate intensity physical activity to a target of 300 minutes per week.; Participants in this group will be instructed to limit energy intake to 20% of estimated baseline energy requirements on three non-consecutive days per week, and to eat ad libitum the other 4 days per week. Participants in this group will also receive a 12 month comprehensive group based behavioral weight loss program and will be instructed in specific strategies to support IMF. Randomized groups will meet separately. Participants in this group will also be asked to increase moderate intensity physical activity to a target of 300 minutes per week.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment