Have you felt stuck in your weight loss journey despite counting calories or following strict diets?
Intermittent fasting is not a passing trend, but a science-backed protocol that
optimizes your metabolism, improves hormonal health, and activates natural fat-burning mechanisms.

At Nutrenza, we’re here to guide you and suggest products that have worked for us. Each link will take you to a recommended product.

In this technical yet clear guide, you’ll discover how the body responds to fasting, the different available methods (like the popular 16:8 or the OMAD protocol), and how to safely integrate them into your daily life.
If you’re looking for a sustainable tool to transform your health and body composition, this is your starting point.

Get ready to understand fasting like never before — with evidence, precautions, and practical strategies. And best of all: without counting a single calorie.

What Is Intermittent Fasting?

Intermittent fasting is a nutritional protocol that alternates between eating periods and fasting periods.
Unlike traditional diets that focus on what to eat, intermittent fasting emphasizes when to eat, regulating intake windows to optimize internal metabolic processes.

On a physiological level, insulin levels decrease during fasting, promoting fat mobilization. Additionally, processes like autophagy are activated—a cellular recycling mechanism that can have positive effects on longevity and chronic disease prevention.

Numerous clinical studies have shown that intermittent fasting can improve insulin sensitivity, reduce the risk of cardiovascular disease, and significantly aid in weight control [see study].

For those seeking a deep understanding of this method, one of the most recommended books is The Complete Guide to Fasting by Dr. Jason Fung—an essential reference in the scientific and nutritional community. You can also explore:

• 📘 Fast This Way – Dave Asprey: a biohacker’s guide to using fasting as a tool for energy and mental control.
• 📗 Fasting as a Lifestyle: a collaborative approach between doctors and patients, with real testimonials and practical protocols.

Understanding fasting as an evolutionary practice, aligned with our biological design, completely changes the perspective on “dieting.” It’s a metabolic reprogramming tool, validated by modern science.

History and Physiological Foundations of Intermittent Fasting

Intermittent fasting is not a modern invention. In fact, it is an ancestral practice that is part of our evolution as a species. For millennia, humans naturally went through prolonged periods without access to food, training the body to use multiple energy sources, including stored body fat.

From a physiological standpoint, when the body enters a fasting state (after 12–14 hours without consuming calories), blood glucose levels drop, reducing insulin secretion. This activates alternative metabolic mechanisms, such as the release of fatty acids and the production of ketones in the liver.

In this state, the body not only preserves muscle mass but also improves energy efficiency and promotes processes like autophagy—an internal cellular cleansing system that contributes to longevity and the prevention of degenerative diseases.

Ancient religions such as Islam, Buddhism, and Christianity have practiced fasting for spiritual and purification purposes. Modern science now supports many of its beneficial effects on metabolic, immune, and neurological health.

To explore the physiology of fasting further, we recommend the book “The Longevity Challenge” by Dr. James DiNicolantonio, which explores fasting’s impact on longevity and cellular regeneration.

Types of Intermittent Fasting: Which One Is Right for You?

There are various intermittent fasting protocols, each structured differently based on fasting duration and eating windows. Choosing the right one depends on your goals, experience, and lifestyle. Here are the most popular and effective options:

If you’re looking for specific guides to implement these protocols, the book “The Intermittent Fasting Guide for Beginners” includes detailed plans for each fasting method. Ideal for those seeking a safe and structured start.

How Does Intermittent Fasting Affect Fat Loss?

Intermittent fasting stimulates body fat loss through several key physiological mechanisms. During fasting, insulin levels — the hormone responsible for fat storage — decrease significantly, allowing the body to access its energy reserves stored as triglycerides.

By reducing the frequency of meals, you extend the period in which your body remains in a fat-burning state (lipolysis), especially once liver glycogen stores are depleted (typically after 12–16 hours of fasting).

Fasting also boosts the release of growth hormone (GH), which helps preserve muscle mass and improves fat oxidation. Recent studies have shown that even 16-hour fasts can increase GH levels by up to 300% in men [see study].

Unlike constant low-calorie diets, intermittent fasting allows for alternating periods of restriction and nourishment, reducing the risk of metabolic adaptation (when the body slows down metabolism to conserve energy).

“Intermittent fasting is one of the most effective tools for reducing visceral fat without significant muscle loss.”
— Dr. Eric Berg, metabolic health specialist

For those looking to speed up results, it’s recommended to combine intermittent fasting with products that don’t break the fast but enhance fat oxidation, such as:

• 🧪 Perfect Keto Exogenous Ketones – Ideal for entering ketosis faster and maintaining energy while fasting.
• 💧 LMNT Electrolytes – Calorie-free hydration that maintains performance without breaking the fast.
• 📱 Intermittent Fasting Tracker – A fasting planner and tracker, great for monitoring your progress.

Hormonal and Metabolic Impact of Intermittent Fasting

Intermittent fasting triggers a series of hormonal changes that improve metabolism, promote longevity, and support fat loss without sacrificing muscle mass. These hormonal responses are one of the key reasons fasting is so effective and sustainable long term.

🔻 Insulin Reduction

When no food is consumed, insulin levels naturally decline. This allows the body to enter lipolysis—the process of converting stored fat into energy. Low and stable insulin levels are also linked to lower systemic inflammation and improved glucose sensitivity.

📈 Increase in Growth Hormone (GH)

Fasting can increase growth hormone production by 300–500%, promoting cellular regeneration, fat loss, and muscle preservation. GH also enhances bone density and skin elasticity.

🧬 Autophagy Activation

Autophagy is a process where cells break down and recycle damaged or dysfunctional components. It’s especially active during prolonged fasting and has been linked to cancer prevention, neurodegenerative disease protection, and slower aging. [see study]

🧠 Leptin and Ghrelin Regulation

Intermittent fasting improves response to leptin (satiety hormone) and reduces ghrelin (hunger hormone), helping to naturally control appetite. This hormonal balance improves adherence and reduces food anxiety.

To support these hormonal benefits and ease your transition into fasting, consider using natural supplements like:

• 🌿 Alpha Lipoic Acid – Antioxidant that improves insulin sensitivity.
• 🧬 Liposomal Vitamin C – Strengthens immune function during fasting.
• 🔬 Chelated Magnesium – Enhances sleep, reduces stress, and supports hormonal balance.

Proven Benefits of Intermittent Fasting

Intermittent fasting isn’t just useful for losing weight—it also improves fundamental health markers. Various clinical studies have demonstrated its positive effects in areas ranging from metabolic health to brain function.

⚖️ Body Fat and Visceral Fat Loss

Several studies have shown that intermittent fasting can reduce body weight by 4–8% in 8 to 12 weeks, particularly targeting visceral fat (the most dangerous kind). [see study]

🩺 Improved Lipid Profile and Insulin Sensitivity

Fasting has been shown to reduce triglycerides, lower LDL cholesterol, and raise HDL cholesterol. It also improves insulin resistance, helping prevent and manage type 2 diabetes. [see study]

🧠 Neuroprotection and Cognitive Function

Fasting boosts production of BDNF (brain-derived neurotrophic factor), a protein that supports neuron regeneration, protects against Alzheimer’s, and enhances mental clarity.

❤️ Cardiovascular Health

It improves blood pressure, reduces inflammation, and lowers markers such as C-reactive protein (CRP), associated with cardiovascular risk.

🧬 Cellular Aging and Longevity

Fasting activates genes linked to cellular repair (sirtuins, AMPK) and is associated with increased lifespan in animal models. These benefits are increasingly being validated in humans.

If you want to maintain these benefits long-term, consider complementing your routine with:

• ⌛ Organic MCT Oil – Ketogenic energy source that doesn’t break the fast and enhances brain function.
• 💊 Resveratrol + NMN – Mitochondrial-targeted anti-aging supplements.
• 🔍 Keto Mojo Ketone Meter – Ideal for tracking ketosis and optimizing results.

Myths and Facts About Intermittent Fasting

Despite growing scientific evidence, intermittent fasting is still surrounded by myths that cause confusion. Here we debunk the most common ones with technical support.

❌ Myth 1: “Skipping breakfast slows your metabolism”

Fact: Studies show that fasting can actually improve metabolic efficiency by activating hormones like norepinephrine and growth hormone. The human body is adapted to go hours or even days without food. [see evidence]

❌ Myth 2: “You lose muscle if you don’t eat every 3 hours”

Fact: The body prioritizes glucose and fat for energy. As long as there’s energy available, it doesn’t break down muscle. Plus, fasting increases growth hormone, which protects lean mass.

❌ Myth 3: “Fasting means starving”

Fact: Most people report a decrease in appetite once they adapt to fasting. This is due to better regulation of hunger (ghrelin) and satiety (leptin) hormones.

❌ Myth 4: “Fasting isn’t safe for women”

Fact: Women can benefit from fasting with specific adaptations (e.g., shorter or non-daily fasts). The key is to listen to your body and avoid forcing the protocol.

📚 For further learning:

• 💡 “The Fast Diet” – The book that popularized the 5:2 method, perfect for debunking myths.
• 🎧 Audible Audiobook: Intermittent Fasting – Beginner’s Guide – Great for learning while driving or exercising.

Contraindications and Precautions for Intermittent Fasting

Although intermittent fasting offers numerous benefits, it’s not suitable for everyone. It must be implemented responsibly and, in some cases, under medical supervision. Here’s when fasting is not recommended or when the protocol needs to be adapted.

🚫 People who should avoid fasting without supervision:

• 👶 Minors under 18 years old
• 🤰 Pregnant or breastfeeding women
• 🧠 People with a history of eating disorders (anorexia, bulimia)
• 🧪 Individuals with untreated severe hypoglycemia
• 🏥 Patients with uncontrolled chronic illnesses (type 1 diabetes, kidney failure, etc.)

🔍 General precautions:

Before starting an intermittent fasting protocol—especially if planning extended fasts or taking medications—it’s best to consult a doctor or a specialized nutritionist.

The first few weeks may bring adaptation symptoms like headaches, fatigue, irritability, or dizziness. To minimize these, we recommend:

• Staying hydrated with sugar-free electrolytes
• Using natural mineral salts
• Consuming diluted apple cider vinegar

📌 Important:

Fasting should never be used as punishment for eating, nor as an emotional control tool. It must be practiced with self-awareness, knowledge, and sustainable health goals.

How to Start Intermittent Fasting: Step-by-Step Guide

Getting started with intermittent fasting doesn’t have to be difficult or extreme. Here’s a progressive guide to adapt safely and sustainably—without harming your metabolism or emotional well-being.

🗓 Week 1: Adjust your schedule

• Delay breakfast by 1 hour each day.
• Avoid late-night snacks—your last meal should be before 8:00 PM.
• Focus on real food: no processed items or added sugars.

🗓 Week 2: Introduce the 16:8 protocol

• Fast for 16 hours (e.g., from 8:00 PM to 12:00 PM the next day).
• Eat within an 8-hour window: 2 to 3 nutritious meals.
• Hydrate with calorie-free electrolytes to avoid fatigue.

🗓 Week 3 and beyond: Personalize your protocol

• Evaluate how you feel: More energy? Better digestion? Adjust the eating window as needed.
• Try other formats like 18:6 or 20:4 once you’re comfortable with 16:8.
• Consider a full-day (24h) fast if you’re experienced and responding well.

📱 Recommended tools to get started:

• 📲 Fastic App – A fasting tracker with reminders and tips.
• 🧪 Keto Mojo Ketone Meter – Great for tracking if you’re burning fat.
• 📖 Intermittent Fasting Journal – Motivational guide and planner.

Remember: success with intermittent fasting isn’t about “enduring hunger,” but about retraining your body and habits. The key is consistency and listening to your body’s signals.

What Can You Consume During a Fast?

One of the most common questions is: Does this break my fast? The key is to avoid anything that spikes insulin or disrupts autophagy or ketosis. Here’s what’s allowed and what should be avoided to maintain fasting benefits.

✅ Allowed (does not break the fast):

• 💧 Plain, mineral, or sparkling water (unsweetened)
• ☕ Black coffee with no sugar or milk
• 🍵 Green, white, or black tea (unsweetened)
• 🧂 Calorie-free electrolytes like LMNT
• 💊 Supplements without calories or added sugars
• 🥄 1 tbsp of MCT oil (if used for performance or adapting to ketosis)

⚠️ Use with caution / flexible fasting only:

• 🍋 Water with lemon (may slightly trigger insulin)
• 🍶 Natural bone broth (provides collagen and electrolytes, but contains calories)

❌ Completely avoid:

• 🍬 Juices, plant-based drinks, diet sodas
• 🥛 Milk, cream, protein powders
• 🍯 Any kind of sweetener (even stevia may disrupt autophagy in some cases)

If you’re unsure about a specific product, you can scan its label with an app like Fastic, which will tell you whether it breaks your fast.

“True fasting is not the total absence of consumption, but the absolute presence of intention.”

— Dr. Walter Longo, fasting and longevity expert

Common Mistakes in Intermittent Fasting (and How to Avoid Them)

Although intermittent fasting seems simple, there are frequent mistakes that can limit—or even reverse—its benefits. Avoiding them can be the difference between frustration and transformation.

❌ Mistake 1: Overeating during the eating window

Thinking you can eat “whatever you want” in 8 hours is a major misconception. Fasting doesn’t replace mindful eating. If you overconsume sugars or ultra-processed foods, you’ll lose the metabolic benefits.

❌ Mistake 2: Not staying properly hydrated

Fasting causes water and electrolyte loss. Without replenishing sodium, magnesium, and potassium, you may feel weak or foggy-headed. Solution: LMNT or sugar-free mineral salts.

❌ Mistake 3: Breaking the fast with refined carbs

After many hours without food, your body is in a sensitive state. Breaking your fast with white bread, sweets, or flours can cause insulin spikes and energy crashes. Better option: protein, healthy fats, and vegetables.

❌ Mistake 4: Not getting enough sleep

Poor sleep increases ghrelin (hunger hormone) and decreases leptin (satiety), making fasting harder. Supplements like magnesium glycinate can improve sleep quality.

❌ Mistake 5: Not having a personalized plan

Jumping into long fasts from day one leads to anxiety and dropout. Start with simple protocols like 16:8 and progress based on your experience and how your body responds.

To structure your progress effectively, use tools like:

• 📱 Fastic App – Daily tracking and guidance.
• 📒 Fasting Journal – Log your progress, symptoms, and adjustments.

Remember: fasting is a journey of metabolic self-discovery. Learning from these mistakes makes you stronger—not weaker.