Fasting Mimicking Diet Improves Skin Hydration and Prevents Skin Roughening in Women: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Researchers wanted to know whether a structured fasting protocol — specifically a five-day fasting mimicking diet (FMD) repeated monthly — could produce measurable improvements in facial skin health. Skin aging is driven partly by chronic inflammation, oxidative stress, and reduced cellular turnover, and autophagy triggered by fasting has been proposed as one mechanism that could counter these processes. This trial tested whether three monthly FMD cycles would affect skin hydration and skin texture in healthy middle-aged women compared to a control group eating normally.

Who Was Studied

Participant profile: 45 healthy women, aged 35 to 60 years. All participants were in general good health with no active skin conditions requiring treatment. Skin assessments were conducted at baseline, day 11 (after the first FMD cycle), and day 71 (end of the third monthly cycle).

How the FMD worked in this study: The fasting mimicking diet is a five-day low-calorie, plant-based protocol designed to trigger fasting-like metabolic responses without complete food elimination. Caloric intake during the 5-day FMD period is typically in the range of 800–1,100 kcal/day on day 1 and approximately 700–800 kcal/day on days 2–5, with specific macronutrient ratios formulated to maintain ketosis and reduce IGF-1 signaling while allowing limited food intake.

What the Researchers Found

Skin Hydration

The FMD group showed a statistically significant increase in skin hydration relative to their own baseline at both assessment timepoints:

The hydration benefit strengthened over time. The effect observed at day 11 — after a single FMD cycle — was maintained and remained statistically significant at day 71, suggesting cumulative benefit from repeated monthly cycles.

Skin Texture (Roughness)

The between-group difference for skin roughness was statistically significant (p = 0.032). The FMD did not simply improve skin texture — it protected against the progressive roughening that was observed in the control group over the same period.

Subjective Skin Assessment

Participants completed self-assessments of their skin throughout the trial. The FMD group reported positive changes in overall skin appearance and quality, consistent with the objective instrument-based measurements.

What Did Not Change

The study was focused specifically on hydration, texture, and skin assessment. Acne lesion counts, sebum production, and inflammatory skin biomarkers were not primary outcomes in this trial and were not reported as separate endpoints.

What the Researchers Concluded

Three consecutive monthly cycles of a five-day fasting mimicking diet produced significant improvements in facial skin hydration and prevented the progressive increase in skin roughness seen in the control group. The researchers suggested that the FMD's effects on cellular renewal, inflammation reduction, and metabolic signaling may underlie the observed skin benefits.

What This Means If You Fast

• Periodic fasting may support skin health. A structured monthly fasting period — even just five days — was enough to produce measurable improvements in skin hydration and texture over three months.
• The benefit appears cumulative. Skin hydration improved after the first cycle and remained significantly elevated at the end of the third cycle, suggesting that repeating fasting protocols over months produces compounding effects.
• Fasting protects against age-related skin roughening. The control group's skin became measurably rougher over 71 days — the FMD group's did not. This suggests periodic fasting may play a protective role against one aspect of skin aging.
• Daily IF may also help, through similar pathways. While this study used a 5-day monthly FMD, the underlying mechanisms — autophagy, reduced inflammation, lower IGF-1 — are also triggered by regular 16:8 or 18:6 intermittent fasting. Daily fasting has not been tested head-to-head against FMD for skin outcomes, but the shared biology is relevant.
• Hydration from within matters. Many fasters report skin improvements after months of practice. This RCT provides one of the first controlled human data points supporting that observation, at least for the FMD protocol.
• Women aged 35–60 were the study population. Results may not generalize to men or to younger or older women, though the mechanisms are not inherently sex-specific.

Study Limitations

• Small sample size (n=45 total), limiting statistical power for secondary outcomes
• All-female sample; male participants not included
• Short duration (71 days / 3 months); long-term skin effects unknown
• Significant conflict of interest: co-author William C. Hsu is affiliated with L-Nutra Inc., the company that manufactures the ProLon FMD product; L-Nutra also funded the study
• Specific numerical baseline and endpoint values for skin hydration and roughness were not fully reported in publicly available summaries; full data available only in the complete paper
• No measurement of inflammatory skin biomarkers, sebum, or acne lesions — skin condition mechanistic data is limited
• Participants were healthy women; results may not apply to those with active skin conditions or different metabolic health status
• Self-reported diet compliance was not independently verified in the control group

Source

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. PMID: 36902498

Frequently Asked Questions

Does intermittent fasting improve skin?

This RCT found that a 5-day monthly fasting mimicking diet significantly improved skin hydration and prevented skin roughening in healthy women aged 35–60 over 3 months. Whether daily shorter fasts produce the same effect hasn't been directly tested, but they trigger similar biological pathways including autophagy and inflammation reduction.

How long does it take for fasting to improve skin?

In this study, significant improvements in skin hydration were measurable after just one 5-day FMD cycle (day 11). The benefit persisted and remained significant at day 71 after three monthly cycles.

What is a fasting mimicking diet (FMD)?

A fasting mimicking diet is a 5-day low-calorie, plant-based protocol designed to replicate the metabolic effects of prolonged fasting — including ketosis, reduced IGF-1, and autophagy activation — while still allowing some food intake. Caloric intake is typically 800–1,100 kcal on day 1 and around 700–800 kcal on days 2–5.

Does fasting reduce skin aging?

The control group in this study experienced a significant increase in skin roughness over 71 days, while the FMD group did not. This suggests that periodic fasting may have a protective effect against at least one measurable marker of skin aging.

Can fasting help with acne?

This specific trial did not measure acne outcomes. However, fasting reduces insulin levels and systemic inflammation — both of which are linked to acne severity. Research on low-glycaemic-load diets (which share some metabolic effects with fasting) has shown reductions in acne lesion counts. Fasting's effect on skin conditions is an emerging research area.

Related Research and Articles

• Intermittent fasting benefits for skin
• How intermittent fasting promotes autophagy
• Intermittent fasting and inflammation: the research explained
• Does intermittent fasting slow aging?
• Intermittent fasting and longevity: what the science says

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