https://www.sciencedirect.com/science/article/pii/S002432052600202X
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Summary
This is a systematic review of preclinical animal studies asking whether intermittent fasting (IF) protects the heart and vasculature under cardiac stress conditions. The authors registered the review on PROSPERO, searched MEDLINE/PubMed, Embase and LILACS, and included 32 animal studies covering models such as myocardial infarction, ischemia-reperfusion injury, pulmonary arterial hypertension, doxorubicin cardiotoxicity, obesity/high-fat diet cardiomyopathy, hypertension and atherosclerosis. The studies involved about 451 animals, mostly male mice and rats.
The headline finding is that about 80% of studies reported beneficial cardiovascular effects of IF. Reported benefits included lower blood pressure, reduced cardiac hypertrophy and fibrosis, smaller ischemic injury, improved endothelial function, better lipid/metabolic regulation, and improved cardiac performance after stress. Mechanistically, the review emphasizes reduced inflammatory signalling — NF-κB, IL-1β, TNF-α — and activation of pathways such as SIRT3 and AMPK, with proposed improvements in mitochondrial function, lipid handling and cardiac energy homeostasis.
However, the findings are not uniformly positive. Some studies found neutral or adverse outcomes, particularly in hypercholesterolemic or genetically modified mice such as ApoE−/−, LDLr−/− and LQT3 models. In some of these settings, IF worsened atherosclerosis or arrhythmic phenotypes. One study also reported that alternate-day fasting worsened doxorubicin-induced cardiotoxicity.
The authors conclude that IF may increase cardiovascular resilience under stress, but that the effects depend strongly on fasting regimen, duration, metabolic context and disease model. They call for further experimental and clinical studies before IF can be treated as a safe adjunct intervention in people with cardiovascular disease.
What is novel or useful about the paper
The main novelty is its focus on cardiac stress, rather than general IF benefits. Many IF reviews discuss obesity, insulin sensitivity, ageing or cardiovascular biomarkers; this paper specifically asks what happens when the heart is challenged by infarction, ischemia-reperfusion, cardiotoxic drugs, pressure/pulmonary hypertension, severe dyslipidaemia or other stressors. That is a more clinically relevant question than simply asking whether IF improves routine metabolic markers.
A second useful feature is that it highlights context-dependence. The paper does not simply present IF as cardioprotective. It identifies settings where IF may be harmful or ineffective: severe dyslipidaemia, genetically impaired lipoprotein clearance, LQT3 arrhythmia models, and doxorubicin cardiotoxicity. This is important because it undermines any simplistic “fasting is always protective” interpretation.
A third useful contribution is the attempt to integrate mechanisms across diverse models: inflammation, AMPK/SIRT signalling, autophagy, mitochondrial function, lipid metabolism, endothelial function, apoptosis and fibrosis. The mechanistic picture is not fully resolved, but the review helps map the recurring pathways that appear in the preclinical literature.
Critique
The biggest limitation is that this is a preclinical review, not a clinical evidence base. The authors acknowledge that animal responses vary across species and that direct translation to human cardiovascular disease is uncertain. That matters especially because fasting tolerance, medication interactions, frailty, diabetes treatment, arrhythmia risk and heart failure status would all affect whether IF is safe in real patients.
The evidence base is also heterogeneous. The included studies used different species, strains, ages, sexes, stress models, fasting protocols and durations. Alternate-day fasting, time-restricted feeding, every-other-day feeding and other regimens are biologically different interventions. Pooling them under “intermittent fasting” risks blurring important differences. The review itself notes that diversity in IF protocols complicates comparison and synthesis.
The review’s headline “~80% positive” figure should be treated cautiously. Positive/negative classification can overweight small studies, mechanistic biomarker shifts or model-specific effects. A small mouse study showing improved signalling is not equivalent to a robust survival or functional benefit after myocardial infarction. There does not appear to be a quantitative meta-analysis of effect sizes, so the reader cannot easily judge magnitude, consistency or publication bias.
The sex balance is weak. Most animals were male, while only a minority of studies included both sexes. That is a major limitation because fasting responses, lipid metabolism, cardiac remodelling and drug cardiotoxicity may be sex-dependent. A cardioprotective effect in young male rodents cannot safely be generalized to older females, post-menopausal humans, or mixed clinical populations.
The adverse findings are especially important. IF worsened or failed to improve outcomes in some hypercholesterolemic models, and one doxorubicin model suggested harm. This implies that IF may interact badly with certain metabolic or pharmacological contexts. The paper is strongest when it treats IF as a conditional stress-response intervention, not as a universally beneficial lifestyle measure.
Bottom line
This is a useful review showing that IF often looks cardioprotective in animal models of cardiac stress, especially through anti-inflammatory, mitochondrial, autophagy and AMPK/SIRT-linked mechanisms. But the evidence is heterogeneous, mostly male-rodent based, and not uniformly positive. The most important takeaway is not “IF protects the heart”, but rather: fasting can reshape cardiac stress responses, sometimes beneficially, but the direction depends on the disease model, lipid state, genetic background, drug exposure and fasting protocol.