One of the most well-known caloric restriction diets is Ramadan intermittent fasting, which involves a radical change in the diet of practitioners for one lunar month. As Ramadan fasting represents the fourth of the five pillars of the Islamic faith, infirm individuals are exempt from this religious duty.
1. Fasting and Skin Structural and Functional Adaptation
The skin plays a crucial role in adapting to caloric restriction by maintaining its protective functions. A 2017 study by Forni et al. on caloric-restricted mice revealed changes in the epidermis and dermis, including increased stem cells, faster hair growth, reduced adipocyte reserves, and expanded blood vessels. These changes help the skin maintain thermal balance. Fasting reduced cholesterol synthesis in the skin, impairing the barrier and preventing the stratum corneum from effectively preventing excessive water loss through lipids like ceramides and cholesterol. A different study demonstrated that caloric restriction alleviated skin irritation from retinoid treatment, while still preserving its beneficial effects.
2. Fasting and Wound Healing
In an experimental mouse model, short-term fasting for four consecutive days every two weeks enhanced wound healing, likely due to increased macrophage activity. Specifically, macrophages promoted keratinocyte proliferation through TGF-α and supported angiogenesis via VEGF. In contrast, a 2012 study on caloric-restricted rats showed slower wound healing, which improved when the rats were re-fed prior to wounding. This improvement was linked to higher IGF-1 binding protein 3 (IGFBP-3) levels and increased collagen synthesis. Furthermore, other studies suggested that fasting can reduce collagen formation, with Miltyk and Palka (2000) proposing that a decrease in proline precursors (P5C) affects collagen synthesis. Additionally, Cechowska-Pasko et al. (2003) argued that fasting raises IGFBP-1, limiting IGF-1 availability, and in 2004, they proposed that fasting reduces prolidase activity, impairing collagen production.
healing
3. Fasting and the Immune System
Several studies on prolonged fasting (lasting at least 3 days) followed by re-feeding have demonstrated beneficial effects on the immune system. It decreases IGF-1 and PKA signaling, which supports the renewal of hematopoietic stem cells (HSCs) and promotes the proliferation of NK cells, while also increasing stress resistance, potentially shielding HSCs from chemotherapy-induced toxicity. Moreover, short-term starvation enhances macrophage activity, which aids in wound healing and offers protection against specific infections.
4. Fasting and Skin Growth Regulation
IGF-1 supports growth by preventing apoptosis, enhancing angiogenesis, and stimulating cell proliferation. It works locally, reduces blood sugar levels, and inhibits the breakdown of fats and proteins via the MAPK and PI3K signaling pathways.
A 2007 study by Xie et al. on SENCAR mice showed that 20% caloric restriction for 10 weeks reduced IGF-1 levels and downregulated genes related to the MAPK and PI3K pathways. This reduction suggested that caloric restriction could have an anti-carcinogenic effect by limiting tumor development.
5. Fasting and Skin Aging
Caloric restriction without nutrient deficiency has been associated with a longer lifespan and slower aging, which is a complex process characterized by lower collagen levels (particularly type 1 collagen), the loss of fibrillin-positive structures, and damaged elastin. In a 1995 study, Cefalu et al. demonstrated that long-term 60% caloric restriction in rodents reduced the glycation rate of skin proteins, resulting in a reduced accumulation of aging-related metabolites in collagen. While telomere shortening limits cell replication and contributes to aging, its role in fasting remains unclear, as caloric restriction does not seem to affect telomere length, even though there is an inverse correlation with BMI.
6. Fasting and Skin Effects: A Summary
Caloric restriction and fasting significantly affect the skin by influencing biological processes and potentially improving skin health. Figure 3 summarizes the main effects on skin anatomy, homeostasis, and physiology.
Conclusions
We can identify the following key knowledge gaps : namely, the lack of comprehensive studies and the need for further research in specific areas.
1. There is a significant need for evidence-based recommendations and guidelines. The existing literature on the effects of Ramadan fasting and other fasting regimens on skin diseases is limited and of low quality, including online information.
2. Researchers have conducted few studies, typically involving small convenience samples with high non-responder rates.
3. We should compare the effects of Ramadan fasting on skin health with other types of fasting, such as periodic dieting, calorie restriction, dietary manipulation, intermittent, short-term, and prolonged fasting.
References
1. Maloh, J., Wei, M., Hsu, W. C., Caputo, S., Afzal, N., & Sivamani, R. K. (2023). The Effects of a Fasting Mimicking Diet on Skin Hydration, Skin Texture, and Skin Assessment: A Randomized Controlled Trial. Journal of clinical medicine, 12(5), 1710. https://doi.org/10.3390/jcm12051710
2. Bragazzi, N. L., Sellami, M., Salem, I., Conic, R., Kimak, M., Pigatto, P. D. M., & Damiani, G. (2019). Fasting and Its Impact on Skin Anatomy, Physiology, and Physiopathology: A Comprehensive Review of the Literature. Nutrients, 11(2), 249. https://doi.org/10.3390/nu11020249
3. Cao, C., Xiao, Z., Wu, Y., & Ge, C. (2020). Diet and Skin Aging-From the Perspective of Food Nutrition. Nutrients, 12(3), 870. https://doi.org/10.3390/nu12030870