What does the evidence actually say?

What we hold on intermittent, fasting, weight and loss

Read as:intermittentfastingweightloss

3 vetted claims match all four terms. Strongest evidence first.

1. Metabolic & GLP-1well supported · human data

   In adults with prediabetes or type 2 diabetes, intermittent fasting cut body weight by 4.56 kg and lowered HbA1c, fasting glucose, cholesterol and triglycerides versus control diets, but against straightforward calorie restriction it added only modest extra weight loss and no metabolic advantage.

   What it shows: Meta-analysis of 14 randomised trials (1,101 adults with prediabetes or type 2 diabetes); fat mass, insulin, LDL, HDL and blood pressure did not improve versus control, and versus calorie restriction there were no differences in glycaemic markers, lipids or blood pressure.Meta-analysis · Diabetes Obes Metab

   Full breakdown →Energy balance explained →Calorie Deficit Calculator →

   Source: The effects of intermittent fasting on body composition and cardiometabolic health in adults with prediabetes or type 2 diabetes: A systematic review and meta-analysis. Diabetes Obes Metab 2024
2. Women's Healthpreliminary · human data

   In a meta-analysis of five studies, intermittent fasting reduced body weight by an average of 4.25 kg in women with PCOS, alongside improvements in BMI, insulin resistance, triglycerides, free androgens and inflammation, though total testosterone, cholesterol and waist-to-hip ratio did not change.

   What it shows: Meta-analysis of only five studies; the authors themselves describe the evidence as preliminary, and several hormone and lipid outcomes (total testosterone, cholesterol, AMH) showed no significant change.Meta-analysis · Nutrients

   Full breakdown →Insulin sensitivity explained →Calorie Deficit Calculator →

   Source: Effect of Intermittent Fasting on Anthropometric Measurements, Metabolic Profile, and Hormones in Women with Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis. Nutrients 2025
3. Skin & Glow-uppreliminary · human data

   In a systematic review comparing dietary strategies for psoriasis, ketogenic and continuous calorie-restriction cohorts lost 10-25.6 kg and showed significant falls in Psoriasis Area and Severity Index scores, whereas intermittent fasting cohorts lost 0-2 kg and did not; no serious adverse effects were recorded with any approach.

   What it shows: A systematic review published in protocol form: it reports no number of included trials or participants, includes no head-to-head comparisons, and the authors flag heterogeneity and limited follow-up. The pattern links the amount of weight lost to skin severity rather than proving one diet beats another.Study · J Drugs Dermatol

   Full breakdown →Energy balance explained →Calorie Deficit Calculator →

   Source: Impact of Intermittent Fasting, Keto Diet vs Continuous Caloric Restriction on Psoriasis Severity: A Systematic Review and Meta-Analysis Protocol. J Drugs Dermatol 2026

Related, not an answer to your question

1. Nutritionwell supported · human data

   A network meta-analysis of 92 trials in adults aged 55-70 with overweight or obesity found that combining calorie restriction with resistance or mixed exercise and high protein intake was the most effective strategy for nearly all body-composition outcomes. Energy restriction alone was less effective and tended to decrease muscle mass.

   What it shows: Network meta-analysis of RCTs: 92 studies included, 66 of them (4,957 participants) usable for pooling; interventions lasted only 8 weeks to 6 months, and network comparisons are partly indirect.Meta-analysis · Adv Nutr

   Full breakdown →Sarcopenia explained →Calorie Deficit Calculator →

   Source: Nutrition and Exercise Interventions to Improve Body Composition for Persons with Overweight or Obesity Near Retirement Age: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials. Adv Nutr 2023
2. Metabolic & GLP-1well supported · human data

   A meta-analysis of ten randomised trials found oral small-molecule GLP-1 receptor agonists significantly reduced body weight, waist circumference and HbA1c in adults with type 2 diabetes or obesity, and made a weight loss of 15% or more 10.61 times more likely. Gastrointestinal side effects rose sharply, but serious adverse events did not increase.

   What it shows: Meta-analysis of ten RCTs in adults with type 2 diabetes or obesity; the abstract does not report total participant numbers or trial durations, and gastrointestinal side effects were substantially more common on the drugs.Meta-analysis · Front Endocrinol (Lausanne)

   Full breakdown →Insulin sensitivity explained →Calorie Deficit Calculator →

   Source: Investigation into the efficacy and safety profile of oral small-molecule GLP-1 receptor agonists in type 2 diabetes and obesity: a systematic review and meta-analysis. Front Endocrinol (Lausanne) 2026
3. Gut & Microbiomewell supported · human data

   Pooling 8 randomised trials in women with polycystic ovary syndrome, probiotic or synbiotic supplements produced small reductions in fasting blood sugar (-2.52 mg/dl), insulin (-2.27 uIU/mL), HOMA-IR (-0.69), C-reactive protein and total testosterone (-0.12 ng/mL). Weight and body mass index did not change significantly.

   What it shows: Meta-analysis of only 8 RCTs (nine treatment arms) in women with polycystic ovary syndrome, searched to September 2018. The individual trials were small and short, effect sizes are modest, strains and doses varied between studies, and the findings do not transfer to women without PCOS.Meta-analysis · Eur J Clin Nutr

   Full breakdown →Insulin sensitivity explained →Metabolic Fitness Index →

   Source: Effect of probiotics and synbiotics on selected anthropometric and biochemical measures in women with polycystic ovary syndrome: a systematic review and meta-analysis. Eur J Clin Nutr 2020
4. Metabolic & GLP-1well supported · human data

   In 10 randomised trials with 599 adults with prediabetes or type 2 diabetes, time-restricted eating windows of 4-10 hours lowered fasting blood glucose by 0.30 mmol/l and body weight by 1.6 kg, but produced no significant overall change in HbA1c. HbA1c did fall modestly in the prediabetes subgroup only.

   What it shows: Meta-analysis of 10 RCTs totalling 599 adults, mean study length 4 months, graded moderate certainty; confidence intervals in several included trials were wide because samples were small, and effects on insulin sensitivity, beta cell function and continuous glucose monitoring were inconclusive.Systematic review · Diabetologia

   Full breakdown →Insulin sensitivity explained →Metabolic Fitness Index →

   Source: Effects of time-restricted eating on markers of glucose metabolism and regulation in individuals with prediabetes or type 2 diabetes: a systematic review and meta-analysis of randomised controlled trials. Diabetologia 2026
5. Metabolic & GLP-1preliminary · human data

   Pooling 13 randomised trials in people with simple obesity, adding massage to a lifestyle programme was associated with larger falls in body weight (mean difference -4.85 kg) and BMI (-2.65) than lifestyle change alone, along with reductions in waist circumference, total cholesterol, triglycerides, LDL cholesterol, fasting insulin and HOMA-IR. HDL cholesterol also fell rather than rose.

   What it shows: Thirteen mostly small randomised trials drawn largely from Chinese-language databases, mixing adults with children and adolescents, and with extreme statistical heterogeneity for the blood-lipid outcomes (I² up to 98.3%); effects this large from adding massage are hard to explain and need independent replication before being taken at face value.Meta-analysis · Medicine (Baltimore)

   Full breakdown →Insulin sensitivity explained →Calorie Deficit Calculator →

   Source: Comparative effectiveness of massage combined with lifestyle intervention and lifestyle intervention alone for simple obesity: A systematic review and meta-analysis. Medicine (Baltimore) 2025
6. Metabolic & GLP-1preliminary · human data

   Six months of the 5:2 diet was associated with weight loss of -6.3% in overweight or obese adults with type 2 diabetes and -5.0% in those without, alongside improvements in waist circumference, blood pressure, HDL and LDL cholesterol and adiponectin. HDL and adiponectin improvements were still present at the 12-month follow-up in both groups.

   What it shows: Secondary analysis of a non-randomised six-month controlled trial: 97 recruited, 93 completed and 82 returned at 12 months, and everyone followed the same 5:2 diet with no non-fasting comparison arm, so the changes cannot be separated from weight loss.Clinical trial · Int J Mol Sci

   Full breakdown →Metabolic syndrome explained →Calorie Deficit Calculator →

   Source: The 5:2 Diet Reduces Risk Factors for Cardiovascular Disease in Subjects with and Without Type 2 Diabetes-A Non-Randomized Controlled Trial. Int J Mol Sci 2026
7. Metabolic & GLP-1preliminary · human data

   An umbrella review of 78 meta-analyses covering 177 373 participants found app-based interventions improved blood pressure, HbA1c, fasting and post-meal glucose, bodyweight, waist circumference, physical activity, diet quality, mood and medication adherence versus controls. There was no significant effect on cardiovascular mortality, cholesterol or triglycerides, body fat, hospitalisation or smoking abstinence.

   What it shows: An umbrella review of existing reviews, so quality is inherited: only 1% of the 78 included reviews was rated high quality and 73% critically low, heterogeneity was very high for most outcomes, and several authors are employed by a food company.Study · Lancet Digit Health

   Full breakdown →Metabolic syndrome explained →Metabolic Fitness Index →

   Source: Effectiveness of app-based interventions for glucose management, cardiometabolic and mental health, and related risk factors: an umbrella review with meta-analysis. Lancet Digit Health 2026

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