#247 Fact or Fad: Intermittent fasting for sustained weight loss
CLINICAL QUESTION
Does intermittent fasting result in greater sustained (>6 month) weight loss than continuous dieting in adults?
BOTTOM LINE
Although inconsistently defined, intermittent fasting (example 500 kcal/day for 2 days/week) and continuous dieting (~25% reduction in caloric intake daily) result in similar weight loss, usually ~5-9kg at 6 months-1 year. Discontinuation rates with both diets is up to ~60%.
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EVIDENCE
“Fasting” generally refers to reducing caloric intake by ~75% of caloric needs/day; “continuous dieting” generally refers to reducing caloric intake by ~25%/day.
Systematic review of 9 randomized, controlled trials (RCTs) at least 6 months in duration, 981 patients.1 Example regimen: fasting 2 days/week interspersed with 5 days/week regular intake. After 6 months-2 years:
- No difference in mean weight loss.
- Mean weight loss range in both groups: 2.1-26.6 kg.
- 5/6 RCTs: mean weight loss ranged ~5-9 kg in both arms, not statistically different.2-6
- Best quality RCT, 100 patients, randomized to alternate-day fasting, continuous dieting, or no intervention control for 6 months.2 After additional 6-month follow-up:
- Weight loss between fasting and continuous dieting: no difference.
- Both diets lost ~6% more than no intervention.
- Weight loss between fasting and continuous dieting: no difference.
- 1 RCT, 51 men, both groups decreased calories by 33%. Intermittent fasting (alternating 2-week blocks of fasting with regular diet) or continuous diet for 16 weeks.7 After 6-month follow-up:
- Statistically significant difference in weight loss: 11 kg versus 3 kg (continuous).
- Only patients who completed the study were included in the analysis.
- Best quality RCT, 100 patients, randomized to alternate-day fasting, continuous dieting, or no intervention control for 6 months.2 After additional 6-month follow-up:
- Discontinuation rates 30-60%.1,3,4
- Weight loss for most diets peaks ~ 6 months,1 then slow regain.3,6,7
- No weight loss diet appears superior to another across populations, however individual results vary widely.8
- Mediterranean diet is the only diet that reduces cardiovascular disease.9
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