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18 July 2025

Is Intermittent Fasting Really Healthy? The Truth According to Science

Intermittent fasting has gained increasing popularity in recent years — not just as a weight loss strategy, but also as a potential ally for metabolic health and longevity. But is this practice truly healthy? What does science say behind the trend?

In this article, we explore the key studies and evidence on intermittent fasting — its benefits, risks, and in which cases it may (or may not) be a good choice.

What is intermittent fasting?

Intermittent fasting is not a diet in the traditional sense. It is a meal pattern that alternates between periods of eating and periods of fasting.

The most common methods include:

• 16:8 – 16-hour fast with an 8-hour eating window
• 5:2 – regular eating 5 days a week and calorie restriction (500–600 kcal) on 2 days
• 24h or more – full-day fasting 1 or 2 times a week

What happens in the body during fasting?

When the body enters a fasting state, there are major shifts in energy usage:

• Lower blood insulin levels
• Increased norepinephrine release, which enhances fat burning
• Glycogen depletion followed by increased fat use as the primary energy source
• Boosted cellular autophagy — the body's natural “clean-up” process

These effects explain much of the health potential attributed to intermittent fasting.

Science-backed benefits

Several studies, both in humans and animals, indicate that intermittent fasting may offer benefits such as:

✔️ Reduced body weight and visceral fat

• Especially effective when combined with balanced eating and physical activity

✔️ Improved insulin sensitivity

• Helps stabilize blood sugar levels
• Can benefit people with prediabetes or insulin resistance

✔️ Decreased chronic inflammation

• Studies show a reduction in inflammatory markers after 2 to 4 weeks

✔️ Neuroprotective potential

• Fasting may promote BDNF production (brain-derived neurotrophic factor), linked to brain health and protection against neurodegenerative diseases

✔️ Increased lifespan (in animal models)

• Studies in rodents show intermittent fasting may extend life span and reduce age-related disease risks

But... is it healthy for everyone?

Despite the benefits, intermittent fasting is not suitable for everyone. There are situations where it can pose risks or discomfort:

• People with a history of eating disorders (e.g., bulimia, anorexia)
• Pregnant or breastfeeding women, and children
• Individuals with type 1 diabetes or those taking glucose-lowering medication
• Those with digestive conditions or kidney disease

Additionally, many people report symptoms such as fatigue, irritability, headaches, and trouble concentrating during the first few weeks — especially without proper nutritional guidance.

What is science still investigating?

Although research is promising, there are still limitations and gaps:

• Most studies are short term
• There’s a lack of studies involving female-specific responses (due to hormonal variations)
• The long-term effects on metabolism, fertility, and cognitive function are still being studied

Conclusion: is intermittent fasting healthy?

Yes, it can be healthy — if done consciously, with support, and adapted to your lifestyle.

Intermittent fasting is not a magic fix, but it can be an effective strategy for those looking to improve metabolic health, manage weight, and increase daily energy levels.

Before starting, it's essential to consult a healthcare professional — especially if you have any medical condition or take medication. And remember, Misericórdias Saúde is here to help guide you.

💬 Every body is unique — what works for one person may not work for another.