Periodic Plant-Based Fasting, An Intermittent and Traditional Path to Heart Health and Longevity
- Alastair Hunt
- 1 day ago
- 7 min read
Updated: 7 hours ago
In a new study, scientists have explored how short-term restriction of animal products affects our bodies at the molecular level. Conducted among individuals in Greece who follow traditional religious fasting traditions, the research uncovers promising links between periods of plant-based eating and better cardiometabolic health.
As ever, please talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle, especially if you are under treatment. Links to all studies at bottom of page.
How Traditional Fasting Became a Model for Modern Health Research
The participants in this study offered researchers a rare and valuable opportunity. They were drawn from a community in Northern Greece where many individuals follow the dietary traditions of the Greek Orthodox Church. These traditions involve highly structured, long-term patterns of periodic fasting from animal products, beginning often in childhood and continuing throughout adult life.
Specifically, participants alternated between an omnivorous diet and restricting meat, dairy, fish and eggs for approximately 180 to 200 days each year. Fasting periods were closely tied to religious observances, including Lent, Advent and other designated fasts, as well as every Wednesday and Friday. Importantly, during fasting, foods like vegetables, fruits, legumes, grains, nuts, olive oil and shellfish (such as mussels and clams) remained on the menu, while foods from land animals and fish with backbones were excluded.
What makes this population particularly remarkable is the consistency and long-term adherence to this fasting pattern. Unlike participants in typical short-term diet studies, these individuals had practiced dietary shifts reliably for at least ten years, often much longer, following strict guidelines passed down through family and community tradition. This built-in dietary structure mimicked the design of a formal intervention study - but without requiring artificial restrictions or changes for the purpose of research.
Crucially, energy intake was not deliberately reduced during fasting; participants ate to satisfaction, adjusting naturally to the available plant-based foods. The lifestyle also included elements typical of a Mediterranean way of life: moderate alcohol intake, low smoking rates, high physical activity and an emphasis on seasonal, minimally processed foods.
Together, these factors created a natural model of intermittent plant-based eating, allowing researchers to examine how short but regular periods of animal product restriction impact human metabolism in real-world conditions.
Healthier Lipid and Amino Acid Profiles
One of the study's standout findings was a sharp drop in various lipid molecules during periods of animal product restriction. Notably, LDL cholesterol levels dropped more significantly than HDL cholesterol, a shift linked to lower risk of cardiovascular disease. Other lipid-related changes, such as decreases in sphingomyelins and phospholipids, reinforced the heart-health benefits.
Levels of branched-chain amino acids (BCAAs) also declined by about 7%, with valine and leucine leading the reduction. High BCAA levels have previously been associated with obesity, diabetes and heart disease. Lowering them could therefore support better metabolic outcomes.
These molecular shifts mirrored patterns seen in people who permanently follow vegan diets, suggesting that even temporary animal product restriction can deliver some of the same biological advantages.
Understanding the Benefits
To measure the health impact more precisely, researchers applied a validated biomarker score (Deelen et al) based on 14 key blood molecules known to predict overall mortality risk. Improvements in this score reflected a lower biological risk of death. Some of the most important biomarkers included:
VLDL Size – smaller particles linked to better fat metabolism.
Small HDL Lipid Content – higher levels suggest improved heart protection.
Branched-Chain Amino Acids (Valine, Leucine, Isoleucine) – lower levels are healthier for metabolism.
Phenylalanine – lower levels reduce inflammation risk.
Histidine – higher levels support anti-inflammatory action.
Acetoacetate – balanced levels show good fat-burning ability.
PUFA to Total Fat Ratio – higher ratios are beneficial for heart and brain health.
In simple terms, these markers provide a 'molecular health snapshot' and during fasting periods, participants’ profiles shifted in a direction linked to longer, healthier lives.
Lower Risk of Mortality and Cardiometabolic Diseases
Using this biomarker analysis, the researchers found that fasting periods significantly improved participants’ metabolic health scores. Additionally, profiles linked to fasting moved away from those associated with heart attack, stroke and diabetes risk. Although improvements in blood chemistry do not guarantee disease prevention, these biological changes are encouraging signs.
Powerful Hormonal and Protein-Level Changes
Beyond fats and amino acids, the study identified significant shifts in several key proteins. Most notably, levels of the hormone FGF21 surged during fasting. FGF21 is associated with improved blood sugar regulation, fat metabolism and even longevity in animal studies.
Interestingly, 23% of the proteins altered were known drug targets, suggesting that diet could influence pathways usually targeted by medications for age-related diseases.
Other important changes included reductions in inflammatory proteins like HAVCR1 and PLA2G1B, hinting at a natural anti-inflammatory effect.
Practical Lessons: How We Can Adapt These Insights
This study offers a clear message: adopting structured, periodic breaks from animal products - without necessarily becoming fully vegan - may deliver meaningful health benefits. Readers could consider planning short periods (even just a few weeks) focusing on plant-based meals built around vegetables, legumes, whole grains, nuts and olive oil. In some respects, this diet is similar to the 5:2 longevity diet as formulated by Prof. Luigi Fontana.
Notably, shellfish and molluscs, rich in essential minerals, were included in the fasting diet - a good tip for anyone adopting a more seafood focused practice. Taking care to supplement with vitamin B12 and calcium during longer periods of animal product avoidance could also help balance potential risks.
Low smoking rates, moderate alcohol intake, and the Mediterranean diet rich in olive oil and seasonal produce also formed part of the healthier lifestyle observed in the study participants - further habits that we may wish to emulate.
Potential Downsides
The study found that increased oxytocin levels during fasting were linked to a higher genetic risk of lacunar stroke, a small-vessel type of brain stroke. Changes in bone-related proteins also suggested that prolonged or extreme avoidance of animal products could weaken bone health over time.
While short periods of plant-based eating appeared mostly beneficial, anyone considering longer-term restriction should ensure they maintain key nutrients like calcium, vitamin D and B12, and seek professional advice to protect both heart and bone health.
Why These Findings Matter
One of the most exciting aspects of this research is how quickly metabolic reprogramming occurred. Within just three to four weeks, blood profiles shifted markedly - and these changes reversed when participants resumed a regular omnivorous diet.
The findings highlight the power of short, intentional dietary periods to support health, and they underline the importance of balance. While plant-focused eating can improve inflammation and cholesterol profiles, care must be taken to ensure full nutritional adequacy over the long term.
Final Thoughts
This study shines a light on how periodic restriction of animal products - even without reducing overall calorie intake - can prompt significant, potentially beneficial changes in our bodies. While promising, these results also remind us that dietary changes should be thoughtfully considered, especially over the long term.
Temporary shifts toward more plant-based eating may offer a practical and sustainable strategy for many people seeking better heart and metabolic health. However, ensuring sufficient intake of key nutrients like vitamin B12, calcium and essential amino acids remains crucial. As more research emerges, personalised approaches to nutrition will likely become even more important in promoting long, healthy lives.
Changing health for the better it about progress, not perfection, and even small changes can make a meaningful difference over time. For most people, improving health is about finding motivation and prioritising self-care - with an ultimate goal of taking action. If you want to take effective and targeted steps that fit into your unique lifestyle and circumstances, The Whole Health Practice is here to help.
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Stay Healthy,
Alastair
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Related Studies
Rouskas K, Bocher O, Simistiras A, Emmanouil C, Mantas P, Skoulakis A, Park YC, Dimopoulos A, Glentis S, Kastenmüller G, Zeggini E, Dimas AS. Periodic dietary restriction of animal products induces metabolic reprogramming in humans with effects on cardiometabolic health. NPJ Metab Health Dis. 2025;3(1):14. doi: 10.1038/s44324-025-00057-2. Epub 2025 Apr 9. PMID: 40225784; PMCID: PMC11981922.
Deelen, J., Kettunen, J., Fischer, K. et al. A metabolic profile of all-cause mortality risk identified in an observational study of 44,168 individuals. Nat Commun 10, 3346 (2019). https://doi.org/10.1038/s41467-019-11311-9
Other
Ravussin E, Redman LM, Rochon J, Das SK, Fontana L, Kraus WE, Romashkan S, Williamson DA, Meydani SN, Villareal DT, Smith SR, Stein RI, Scott TM, Stewart TM, Saltzman E, Klein S, Bhapkar M, Martin CK, Gilhooly CH, Holloszy JO, Hadley EC, Roberts SB; CALERIE Study Group. A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity. J Gerontol A Biol Sci Med Sci. 2015 Sep;70(9):1097-104. doi: 10.1093/gerona/glv057. Epub 2015 Jul 17. Erratum in: J Gerontol A Biol Sci Med Sci. 2016 Jun;71(6):839-40. doi: 10.1093/gerona/glw056. PMID: 26187233; PMCID: PMC4841173.
Fontana L, Partridge L, Longo VD. Extending healthy life span--from yeast to humans. Science. 2010 Apr 16;328(5976):321-6. doi: 10.1126/science.1172539. PMID: 20395504; PMCID: PMC3607354.
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