The 2011 paper (Harvie et al., Int J Obes, May 2011) is confirmed as the first peer-reviewed documentation of the 5:2 diet protocol, and Michelle Harvie and Mark Mattson are confirmed co-authors. The PubMed record lists 16 total authors, which means 14 additional co-authors beyond Harvie and Mattson — exactly matching the '14 additional scientists' figure. However, there is a minor nuance: not all 14 additional co-authors are strictly 'scientists' in a narrow sense (some are dietitians/clinicians), and the paper was formally published in May 2011 but was epub'd online as early as October 5, 2010. The core numerical and authorship claim is accurate.

• PubMed (PMID 20921964) lists 16 total authors for the 2011 Harvie et al. paper: Harvie, Pegington, Mattson, Frystyk, Dillon, Evans, Cuzick, Jebb, Martin, Cutler, Son, Maudsley, Carlson, Egan, Flyvbjerg, Howell — confirming Harvie + Mattson + 14 others.
• Wikipedia's Mark Mattson article states: 'The 5:2 diet, a form of intermittent fasting, was first documented in a 2011 article co-authored by Michelle Harvie, Mattson, and 14 additional scientists.'
• Wikipedia's Intermittent Fasting article (the source cited in the claim) states the same: 'It was first documented in a 2011 article co-authored by Michelle Harvie, Mark Mattson, and 14 additional scientists.'
• The paper was published in the International Journal of Obesity (2011;35(5):714–27), confirmed by multiple independent citing sources including PubMed, PLOS ONE, and ScienceDirect.
• The paper's epub date was October 5, 2010, meaning its online availability slightly predates the formal 2011 print publication date, though it is universally cited as 'Harvie et al. 2011'.
• Grokipedia notes that 'a seminal article co-authored by Mattson in 2011 introduced the 5:2 intermittent energy restriction protocol,' corroborating the foundational status of this paper.

The authorship count of '14 additional scientists' is numerically accurate per the PubMed record, but the paper was available online in October 2010 (epub ahead of print), so the '2011' date refers to formal print publication rather than the earliest public availability; no source disputes the 2011 citation convention.

The claim that IF produces weight loss comparable to a calorie-restricted diet is well-supported by the most current and rigorous evidence, including a landmark June 2025 BMJ network meta-analysis of 99 randomised clinical trials. That study found all IF strategies and continuous energy restriction (CER) produced similar weight reductions versus an unrestricted diet, with only alternate-day fasting (ADF) showing a small additional benefit over CER that did not reach clinical significance thresholds. A 2024 meta-analysis in Nutrition, Metabolism and Cardiovascular Diseases further found that IF health benefits are essentially calorie-restriction-dependent, adding important nuance: IF is not superior to CER when calories are matched, and the 'comparable' framing is accurate but incomplete if it implies IF has a distinct mechanism beyond reducing total calorie intake.

• The 2025 BMJ network meta-analysis (Semnani-Azad et al., BMJ 2025;389:e082007) pooled 99 RCTs and found all diet strategies—IF and CER—produced similar benefits in cardiometabolic risk over an unrestricted diet.
• Alternate-day fasting (ADF) was the only IF modality to show additional weight reduction vs. CER (−1.29 kg), but this effect was classified as trivial and did not reach the prespecified 2 kg clinical relevance threshold (BMJ 2025 / PMC12175170).
• A 2024 meta-analysis in Nutrition, Metabolism and Cardiovascular Diseases concluded that 'the health benefits induced by intermittent fasting are calorie restriction dependent' and IF does not provide benefits beyond those of CER when calories are equated.
• An expert commenting via the Science Media Centre noted that 'any strategy reducing calorie intake results in a proportional weight loss,' underscoring that IF's effect is largely explained by reduced total intake rather than meal timing per se.
• When analysis was restricted to trials of 24 weeks or longer, no IF strategy outperformed CER for weight loss, suggesting short-term advantages of certain IF patterns (especially ADF) may diminish over time.
• A 2022 meta-analysis in PMC (NCBI) found IF produced a modestly more significant body weight change vs. CCR (SMD = −0.21), but no significant difference in BMI, illustrating that any edge for IF is small and inconsistent across metrics.

The claim's accuracy depends heavily on which IF protocol is studied (ADF vs. time-restricted eating vs. whole-day fasting), trial duration (advantages for IF shrink in trials ≥24 weeks), and whether calorie intake is truly equated between arms—factors the simple 'comparable' framing does not capture.

The core figures in the claim — −1.51 kg weight loss in men and weight regain within about two weeks — are directly confirmed by a peer-reviewed systematic review and meta-analysis of 35 publications published in Public Health Nutrition (Cambridge University Press, 2012). However, the claim slightly oversimplifies the original finding in two ways: (1) the −1.51 kg figure applies specifically to men, while the overall pooled loss was −1.24 kg (women lost only −0.92 kg), and (2) post-Ramadan follow-up data suggest weight regain timelines ranging from 'no longer than 2 weeks' (the cited meta-analysis) to '2–5 weeks' or even longer in other studies, so 'about two weeks' is accurate for the primary source but not universal across the literature.

• The 2012 meta-analysis of 35 publications (Sadeghirad et al., Public Health Nutrition) found weight loss of −1.51 kg in men and −0.92 kg in women at end of Ramadan, with weight loss lasting no longer than 2 weeks post-Ramadan — directly matching the claim's figures.
• A 2019 MDPI Nutrients systematic review and meta-analysis found return towards or to pre-Ramadan weight at 2–5 weeks after Ramadan, suggesting the '2 weeks' figure from the original meta-analysis is at the earlier end of the range.
• A 2023 Frontiers in Nutrition meta-analysis (LORANS study, 66 studies, 7,611 participants) found weight reductions start to diminish roughly 3 weeks after Ramadan, slightly extending the '2 weeks' window.
• A PMC-hosted replication of the primary meta-analysis confirms: weight loss observed at follow-up (2–6 weeks after Ramadan) was less pronounced, with weight still statistically significantly lower at −0.27 kg compared to pre-Ramadan, indicating partial rather than complete regain at that point.
• Multiple independent systematic reviews and a PubMed-indexed study on East London mosque attendees corroborate that most Ramadan weight loss is regained within weeks post-Ramadan, supporting the general thrust of the claim.

The claim presents the −1.51 kg figure without specifying it is the male-only finding (not the overall pooled estimate of −1.24 kg), and the '~two weeks' regain timeline is drawn from a single 2012 meta-analysis — other meta-analyses using more recent and broader datasets suggest regain may take 2–5 weeks, making 'about two weeks' an accurate but potentially conservative characterisation of the regain window.

The Wikipedia claim that IF 'has not been studied' in children, elderly, or underweight people is an overstatement, but the core caution is well-grounded. Peer-reviewed scoping reviews and clinical trials confirm that research in children/adolescents and older adults exists but is sparse, early-stage, and of low quality — nowhere near the volume or rigor of adult research. Evidence for underweight populations specifically remains essentially absent. Mainstream clinical guidance consistently advises against IF in these groups pending stronger evidence.

• A 2024 Nature npj scoping review found 'limited evidence for its feasibility and efficacy in young people,' covering only 34 studies with 893 participants aged 12–25, mostly of heterogeneous quality (npj Metabolic Health and Disease, Dec 2024).
• A PMC scoping review of IF in youth (ages 15–25) noted that 'studies of IF have mainly focused on adults over the age of 30, and research in youth is still in its early stages' (PMC/NIH, 2024).
• A 2025 MDPI systematic review and network meta-analysis specifically on adults ≥60 years confirmed that 'evidence in older adults remains limited,' with only 7 eligible RCTs found (MDPI Nutrients, April 2026).
• A 2019 NIH-published pilot RCT on time-restricted feeding in older adults (≥65 years) involved only 10 participants, illustrating the nascent and small-scale nature of elder-specific IF research (PMC/NIH, 2019).
• A 2024 Cell Metabolism RCT from the National Institute on Aging examined 5:2 IF in only 40 older adults with insulin resistance, underscoring the very limited sample sizes in this area (PubMed/Cell Metabolism, 2024).
• A 2020 peer-reviewed clinical review stated directly that 'intermittent fasting has not yet been studied in children, adolescents, the elderly, or underweight people and could be harmful in all these populations' (Nursing CE Connection / Wolters Kluwer, 2020).
• Wikipedia's own article text (as of May 2026) reproduces this exact claim, and separately notes that IF 'is not recommended for… growing children and adolescents, the elderly, or individuals with or vulnerable to eating disorders.'

No identified studies specifically examined IF in underweight individuals, so that sub-population of the claim remains essentially unverified beyond expert opinion; and the emerging (if small) body of research in elderly and adolescent cohorts means 'not studied at all' is a meaningful overstatement, even if the overall caution is clinically appropriate.

The claim that intermittent fasting is 'generally safe' on a preliminary basis is broadly consistent with short-term evidence: peer-reviewed reviews from 2024 describe IF as a generally safe dietary approach, and a 2025 systematic review of 56 RCTs found significant improvements in cardiovascular risk factors. However, the overall picture is genuinely mixed: long-term safety data remain sparse, the AHA-linked 2024 observational conference abstract raised a serious signal of a 91% elevated cardiovascular mortality risk associated with 8-hour time-restricted eating, and expert critics noted that this was an unpublished, unreviewed preliminary abstract with important methodological limitations. The word 'preliminary' in the original claim is doing important qualifying work — it is accurate but should not be read as blanket reassurance.

• A 2024 peer-reviewed PMC review (UC San Diego, Microbial Physiology) states that 'available evidence suggests that fasting is often a safe alternative to pharmaceutical interventions in maintaining health and energy balance.'
• A 2025 systematic review and network meta-analysis of 56 RCTs (published in Current Nutrition Reports) found that IF significantly reduced cardiovascular risk factors including body weight, LDL, and blood pressure compared to usual diet.
• A preliminary observational analysis presented at the AHA's EPI|Lifestyle Scientific Sessions 2024 (Zhong et al., NHANES data, n>20,000) found 8-hour time-restricted eating associated with a 91% higher risk of cardiovascular death — a serious but heavily caveated finding.
• Expert critics, including a Stanford cardiologist and a Texas Heart Institute president, questioned the 2024 AHA abstract's methodology and noted it was a conference presentation, not a peer-reviewed publication.
• A 2025 Frontiers in Nutrition commentary explicitly flagged that 'the scarcity of observational studies addressing the effects of long-term application of IF on cardiovascular health has been recognized as a major gap in nutrition research.'
• A Dec 2025 German Institute/Charité study found that time-restricted eating showed no measurable metabolic or cardiovascular benefit when total calories were held constant, adding nuance to general safety and benefit claims.

The most significant limitation is that the AHA-linked 2024 cardiovascular mortality signal came from a conference abstract rather than a full peer-reviewed publication, making it difficult to fully adjudicate its methodological soundness against the broader body of short-term safety evidence; the claim's use of 'preliminary' accurately hedges this uncertainty.