Intermittent Fasting Statistics: Outcomes & Effects

Across 11 meta-analyses of 130 randomized trials, 28 of 104 intermittent-fasting associations (27%) showed significant benefits for weight, fat mass, cholesterol, glucose, insulin or blood pressure

Umbrella review; the median trial lasted 3 months with 38 participants. Intermittent fasting was also associated with reduced fat-free mass.

Only one intermittent-fasting association had high-quality evidence: modified alternate-day fasting for 1-2 months moderately reduced BMI; 72% of significant associations rested on very low-quality evidence

Graded with GRADE criteria. Six associations had moderate-quality evidence.

Intermittent and continuous energy restriction produced comparable weight loss: a non-significant difference of 0.61 kg

Meta-analysis of 11 trials lasting 8-24 weeks; fast days provided 25% or less of energy needs. Fasting insulin fell slightly more (0.89 µU/mL) with intermittent restriction, of uncertain clinical relevance.

12 weeks of 16:8 time-restricted eating produced 0.94 kg of weight loss against 0.68 kg with three structured meals, a non-significant 0.26 kg difference

116 adults with a BMI of 27-43, eating from noon to 8 pm. The authors conclude time-restricted eating alone is not more effective than eating throughout the day.

In the TREAT trial's in-person cohort, appendicular lean mass index fell more with time-restricted eating than with regular meals (difference 0.16 kg/m²)

50 participants measured in person; estimated energy intake did not differ between groups.

Alternate-day fasting and daily calorie restriction produced the same 6.8% weight loss at 6 months, and 6.0% versus 5.3% at 12 months

100 metabolically healthy adults with obesity (mean BMI 34) over a year. Dropout was 38% with alternate-day fasting against 29% with daily restriction.

By month 12, LDL cholesterol was 11.5 mg/dL higher with alternate-day fasting than with daily calorie restriction

Blood pressure, glucose, insulin, triglycerides and C-reactive protein did not differ between the diets. Alternate-day fasters ate more than prescribed on fast days and less on feast days.

An 8-hour eating window (10 am to 6 pm) for 12 weeks cut energy intake by 341 kcal a day and body weight by 2.6% without calorie counting

Pilot study in 23 adults with obesity against matched historical controls. Systolic blood pressure fell 7 mmHg; fat mass, cholesterol and insulin did not change significantly.

All 27 trials of intermittent fasting for overweight and obesity found weight loss of 0.8% to 13.0% of baseline weight, with no serious adverse events

Systematic review of mostly small, short trials (2-26 weeks); 12 that compared fasting with calorie restriction found equivalent results.

Early time-restricted feeding (a 6-hour window ending before 3 pm) improved insulin sensitivity, blood pressure and oxidative stress in 5 weeks even without weight loss

Supervised crossover feeding trial in men with prediabetes, fed enough to keep their weight against a 12-hour control schedule.

A 5-day fast roughly tripled 24-hour growth hormone release (2.82 to 8.75 µg·min/ml) and raised pulse frequency from 5.8 to 9.9 a day

Six healthy men sampled across a fed day and days 1 and 5 of fasting. Somatomedin C (IGF-1) and glucose fell over the fast, so the rise is a starvation response, not an anabolic one.

Ramadan fasting led to an average weight loss of 1.24 kg (1.51 kg in men, 0.92 kg in women), mostly regained within a few weeks

Meta-analysis of 35 studies in healthy adults, most in West Asia.

Eating within a 4-hour window on 4 days a week cut energy intake by about 650 kcal on those days without harming lean-mass retention during 8 weeks of resistance training

Randomized trial in young recreationally active men. The group training without time-restricted feeding gained more lean soft tissue (+2.3 kg, d = 0.25); strength rose in both.

Six small trials shorter than 6 months found intermittent energy restriction equal to continuous restriction for weight loss

Narrative review. Long-term benefits or harms in people with overweight, and especially in normal-weight people, are not known.

Intermittent fasting covers recurring periods of 16-48 hours with little or no energy intake; time-restricted feeding limits daily eating to 8 hours or less

Review of human and animal studies. Periodic fasting, by contrast, lasts 2 to 21 or more days; most of the striking disease benefits come from rodent studies.