Evidence Matters

RCT Results: Does Intermittent Fasting Improve Weight Loss for Those with Overweight or Obesity?

BACKGROUND AND PURPOSE:

Intermittent fasting refers to eating windows separated by defined periods of fasting
- Evidence related to risk and benefits remains limited
Lowe et al. (JAMA Intern Med, 2020) sought to determine the effect of 16:8-hour time-restricted eating on weight loss for individuals who are overweight or obese

12 week randomized controlled trial
Participants
- Men and women aged 18 to 64 years
- BMI: 27 to 43
Interventions
- Consistent meal timing group (CMT)
  - 3 structured meals per day
- Time-restricted eating group (TRE)
  - Eat ad libitum from 12:00 pm until 8:00 pm
  - Completely abstain from caloric intake from 8:00 pm until 12:00 pm the following day
Study design
- Use of mobile application and a Bluetooth scale
  - A subset of participants underwent in-person testing
Primary outcome
- Weight loss
Secondary outcomes (in-person cohort)
- Changes in the following: Weight | Fat and lean mass | Fasting insulin and glucose | Hemoglobin A1c levels | Estimated energy intake | Total energy expenditure | Resting energy expenditure

116 participants | In-person cohort: n = 25 TRE, n = 25 CMT
- Mean age: 46.5 years | 60.3% men
While those in the TRE group had a significant decrease in weight, there was no significant change between groups (P = 0.63)
- Between groups: −0.26 kg (95% CI, −1.30 to 0.78)
Agreement was strong between in-person weight measurements and at-home weight measurements
Aside from appendicular lean mass which was significantly lower in the TRE group (low appendicular lean mass is associated with weakness and disability), there were no significant changes in any of the other secondary outcomes within or between groups
There were no differences in estimated energy intake between groups or other metabolic markers

Time-restricted eating alone, without other interventions, is no more effective for weight loss vs eating throughout the day
The authors conclude

Together, the results of this study do not support the efficacy of TRE for weight loss