Over the past decade, high-fat trends — keto, carnivore, low-carb/high-fat, “butter coffee” lifestyles — have surged in popularity. They promise weight loss, stable energy, sharper focus and metabolic freedom. But emerging research paints a different picture: for many people, especially women aged 30–50, sustained high-fat diets may actually accelerate inflammation, metabolic dysfunction and biological ageing. At Shimalia, we follow data — not trends. And the science shows that excessive dietary fat can work directly against longevity.

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1. High-Fat Diets Can Impair Insulin Sensitivity — Quickly

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Most people believe sugar causes insulin resistance. Research shows fat can cause it first.

 

High-fat meals (especially high in saturated fats) can:

 

• Reduce insulin sensitivity

• Increase liver fat

• Block glucose uptake

• Raise post-meal glucose spikes — even without carbs

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What the science shows:

A controlled human study found that high-saturated-fat diets decreased insulin sensitivity and altered glucose metabolism in healthy individuals within days.

 

This means many people on high-fat diets appear to be in control of blood sugar — but internally, their metabolism is becoming less flexible and more stressed.

 

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2. High-Fat Diets Increase Inflammation — One of the Core Drivers of Ageing

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Chronic inflammation is one of the strongest predictors of biological age.

 

High-fat diets have been shown to:

 

• Increase inflammatory cytokines

• Impair blood vessel function

• Elevate oxidative stress

• Increase risk for metabolic syndrome

 

 

Inflammation is not just a biomarker — it affects sleep, mood, hormones, energy, recovery and immune resilience.

 

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3. The Gut Microbiome Is Highly Sensitive to High-Fat Diets

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Your microbiome regulates immunity, hormones, weight, cravings, mood and longevity.

 

High-fat diets have been shown to:

 

• Reduce beneficial gut bacteria

• Increase inflammatory microbes

• Cause gut permeability (“leaky gut”)

• Disrupt metabolic signalling

 

 

Over time, this contributes to bloating, fatigue, skin issues, hormonal disruption and slower metabolic rate.

 

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4. Lipid Markers Often Rise on High-Fat Diets — Even When Weight Looks Normal

 

 

This is one of the most overlooked issues.

 

People on high-fat diets may still:

 

• Raise ApoB

• Increase LDL / non-HDL cholesterol

• Worsen lipid particle quality

• Increase Lp(a) risk expression

• Show worsening vascular age

• Experience increased hs-CRP inflammation

 

 

These markers are far more predictive of long-term health outcomes than weight or body fat percentage.

 

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5. High-Fat Diets Can Be Particularly Hard on Women’s Hormones

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Women have unique biological needs.

 

Excessive fat intake may:

 

• Disrupt progesterone–oestrogen balance

• Slow thyroid function

• Impair hormonal detoxification in the liver

• Affect cortisol rhythms

• Increase PMS or perimenopause symptoms

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Many women report feeling flat, anxious, puffy, hormonally chaotic or exhausted on long-term high-fat diets — even when they initially felt great during the first few weeks.

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6. Longevity Research Does Not Support Long-Term High-Fat Eating

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Across major longevity research areas — Blue Zones, large cohort studies, centenarian regions, cardiovascular and metabolic literature — the diets associated with longer life consistently include:

 

• Lower saturated fat

• Higher fibre

• High fruit and vegetable intake

• Lean or plant-based proteins

• Low inflammatory load

• Stable metabolic markers

 

 

No long-lived population has ever consumed a long-term high-fat diet.

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The Shimalia Approach: Precision Nutrition for Biological Age Reversal

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Your nutritional plan should be shaped by your biomarkers, not by trends.

 

We use:

 

✓ Blood biomarkers

✓ GlycanAge biological age testing

✓ Withings Body Scan metrics

✓ Hormone analysis

✓ Inflammation and metabolic markers

✓ Personal dietary response

 

…to create an elegant, balanced, anti-inflammatory nutritional framework that supports longevity, energy, hormonal balance and cellular repair.

 

Not extremes.

Not deprivation.

Not fad diets.

Just precision.

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Studies & Scientific Evidence Cited

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Here are the peer-reviewed sources that support the statements above:

 

Metabolic & Insulin Sensitivity

 

Metabolic & Insulin Sensitivity

von Frankenberg et al. Metabolism. 2017.

High-saturated-fat diets decrease insulin sensitivity, even in healthy individuals.

https://pubmed.ncbi.nlm.nih.gov/26615402/

Hernández et al. Journal of Clinical Investigation. 2017.

A single high-fat meal alters liver fat metabolism and reduces insulin sensitivity.

https://www.jci.org/articles/view/89444

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Inflammation

Duan et al. Frontiers in Immunology. 2018.

High-fat diets trigger systemic inflammation and immune dysregulation.

https://www.frontiersin.org/articles/10.3389/fimmu.2018.02649/full

 

Gut Microbiome

Mamun et al. Cells. 2025.

High-fat diets reduce microbial diversity and increase inflammatory species.

https://www.mdpi.com/2073-4409/14/6/463

Basak et al. Nutrition Reviews / ScienceDirect. 2022.

Shows how dietary fats reshape the microbiome and trigger metabolic inflammation.

https://www.sciencedirect.com/science/article/pii/S175646462200096

 

Cardiovascular Markers

Wali et al. Nutrients. 2020.

Mechanisms by which saturated fats increase lipid toxicity, ceramides and cardiovascular risk.

https://www.mdpi.com/2072-6643/12/5/1505

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Additional Landmark Studies (Historical Foundation)

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Randle Cycle Research (Randle et al., 1963) — established that high fatty acid availability inhibits glucose uptake, foundational to understanding insulin resistance.

Boden et al., 1994, 2001

High-fat infusions in humans rapidly cause insulin resistance by increasing free fatty acids.

Mensink & Katan, 1992

Saturated fats increase LDL cholesterol significantly more than other macronutrients.

Vessby et al., 2001

Replacing saturated fat with unsaturated fat improves insulin sensitivity.