Disclaimer: This article is for informational purposes only and is not intended to diagnose any conditions. LifeDNA does not provide diagnostic services for any conditions mentioned in this or any other article.

What Is Fasting?

Fasting has been practiced for thousands of years across cultures and religions, often for spiritual, cultural, or health reasons. In recent years, it has gained popularity as a modern health trend, known for its benefits such as weight loss, improved blood sugar control, increased energy, and even longevity.  However, fasting doesn’t affect everyone the same way. While some individuals feel more energized and focused, others experience fatigue, irritability, or different end results. 

Understanding how fasting impacts your body can help you tailor your eating and fasting schedule for more effective and sustainable outcomes.

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How Does Fasting Work in the Body?

When you eat regularly, your body gets most of its energy from glucose, which comes from the carbohydrates in your meals from food items like  bread, rice, fruits, and sugar. After eating, your body uses this glucose for fuel.

Any extra glucose is stored in your liver and muscles in the form of glycogen. However, when you begin fasting and stop eating for several hours, your body no longer receives that steady stream of glucose from food. In the first 8 to 12 hours of fasting, your body starts using up its stored glycogen to keep your energy levels stable. Once those glycogen stores run low, your body needs to find another way to fuel itself. That’s when it begins breaking down stored fat for energy. 

As your body burns fat, it also produces something called ketones which are natural chemicals made in the liver. Ketones become an important source of energy, especially for your brain, which usually runs on glucose but can also use ketones for energy during fasting. Fasting works by helping your body switch from using sugar to using fat for energy. Along the way, it also balances hormones and promotes natural repair processes. 

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What Are the Benefits of Fasting?

Below are some of the most known common advantages of fasting: 

  • Weight Loss: Fasting helps reduce your calorie intake by limiting the time you eat. During a fast, your body uses stored fat for energy instead of relying on food. This may lead to steady and natural weight loss over time.
  • Lower Inflammation: Fasting may help lower inflammation in the body. By giving your digestive system a break, your body can focus on repairing damaged cells and reducing stress on your immune system.
  • Improved Insulin Sensitivity: Fasting can make your body more sensitive to insulin, the hormone that controls blood sugar. Better insulin sensitivity means your body can manage blood sugar more effectively, which lowers the risk of type 2 diabetes.
  • Better Brain Function: Fasting can increase the production of brain-supporting chemicals and helps improve memory, focus, and overall mental clarity. Fasting may also protect the brain from age-related decline.

Studies on Genetics and  Fasting 

One study looked at whether  fasting is practical for people to follow and whether it affects aging and metabolism. In the study, 24 healthy adults followed a diet where they ate very little one day (25% of normal calories) and much more the next (175%), keeping their total calories stable over time. They also tested whether taking antioxidant vitamins C and vitamins E would affect any benefits of the diet.

The results showed that people could stick to the recommended intermittent fasting diet without major problems, and it didn’t cause weight loss or health issues over the short term. However, other beneficial effects were discovered. Fasting  was noticed to slightly increase the activity of a gene called SIRT3, which helps protect cells and is linked to aging. Fasting  also lowered insulin levels, which could mean better blood sugar control. 

Interestingly, when participants took vitamin C and E supplements (which act as antioxidants), some of these positive effects were reduced. This supports the idea that the mild cellular oxidative stress caused by fasting may actually be helpful, by encouraging the body to activate its own protective systems.

Another study explored the effects of caloric restriction and intermittent fasting on physiological traits in 960 genetically Diversity Outbred mice and investigated how these interventions interact with genetics. Researchers assessed 36 traits covering metabolism, cardiovascular function, motor ability, hearing, and activity. The results showed that caloric restriction and fasting had different and sometimes opposite effects on health, with 40% caloric restriction having the largest physiological impact.

However, not all effects were beneficial or proportional to the level of dietary restriction. Importantly, genetic variation played a major role in 31 of 36 traits that were significantly influenced by heritable genetic differences, with heritabilities ranging from 0.04 to 0.65. The researchers mapped 18 significant genetic loci, including two where the effects depended on the diet, particularly influencing cardiac traits. These gene-by-diet interactions demonstrate that the benefits or drawbacks of dietary interventions are not the same for everyone. Overall, the study shows that both diet and genetics  and especially their interaction shape physiological health responses, emphasizing the need for personalized approaches in dietary interventions.

How to Fast More Effectively Based on Your Genes

Fasting becomes far more effective when it’s personalized. By choosing the right method, tracking your body’s response, syncing with your natural rhythms, and fueling wisely, you can align fasting with your genes unlocking better results and long-term health benefits.

  • Choose a Fasting Style That Suits Your Body: Different fasting methods work better for different people and your genes may influence how your body reacts to fasting. Some people do well with shorter daily fasts, like 14:10 or 16:8, where you fast for part of the day and eat during a set window. These are gentle, easy ways to start and are generally well-tolerated. Others may benefit more from less frequent but longer fasts, such as alternate-day fasting or the 5:2 approach, where calorie intake is reduced on certain days of the week. The key is to listen to your body, start slow, and notice how your energy, hunger, and focus respond. Over time, you can adjust your fasting method to better match your body’s natural tendencies, which may be influenced by your unique genetic makeup.
  • Monitor Key Health Markers:  Tracking your body’s response to fasting can offer valuable insights into how your genes are influencing your progress. Use tools like a health journal to log important data, such as blood sugar levels, ketone production, energy, mood, and hunger. This real-time feedback can help you fine-tune your fasting routine and catch early signs of imbalance, especially if you’re predisposed to issues like hormonal imbalances.
  • Align Your Fasting Schedule with Your Body Clock:  Your circadian rhythm or your body’s internal clock, is partially influenced by genetics. Some people are naturally more efficient at digesting food earlier in the day, while others metabolize nutrients better in the evening. Time-restricted eating, such as eating only between 9 a.m. and 5 p.m., can support your natural rhythms if you have genetic variants tied to circadian-related metabolism. Eating in sync with your internal clock may improve digestion, sleep quality, and blood sugar regulation.
  • Prioritize Nutrient-Dense Foods During Eating Windows:  No matter how “fasting-friendly” your genes are, what you eat during your eating windows matters just as much as when you eat. A poor-quality diet can blunt the benefits of fasting and even increase inflammation. Focus on nutrient-dense, whole foods like fiber-rich vegetables, healthy fats (e.g., avocado, nuts, olive oil), lean proteins (like fish, chicken, or legumes), and complex carbohydrates in moderation. These choices can support stable energy, reduce cravings, and work in harmony with your body’s genetic blueprint.

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