I went on a 14-day fasting retreat - here is how it affected my body

Philippe Roukoz, working in medical content at Aware, went on a 14-day journey to explore the health benefits of fasting and its impact on blood test results. Here’s what he found out.


  • Philippe Roukoz, 28
  • Hobbies: Tennis, Hiking, Piano
  • Occupation: Medical student and medical content at Aware
  • Health goals: Staying fit both physically and mentally

A warning about fasting

Any fast longer than 72 hours must always be performed under medical supervision. Among others, fasting is not recommended for pregnant or lactating people and people with type I diabetes, eating disorders, or some neurological conditions.

This article discusses fasting, covering its methods, potential benefits and cultural practices. It also discusses restrictive eating behaviours, which might be triggering for those with or recovering from eating disorders. Reader discretion is advised. Please prioritize self-care and seek support if needed while reading.

Looking to reconnect with my body and gain more mental clarity, I embarked on a 14-day transformative fasting journey, exploring the connection between what I eat and how I feel. I also used Aware’s blood tests to check how fasting impacted my biomarker levels.

Here’s what I learned.

What is fasting and how does it work?

The fasting method that I followed is called the Buchinger method, named after physician Otto Buchinger who raised awareness around it in the early 20th century. It consists of a restricted diet of up to 350 kcal per day including light soups, vegetable juices, some yogurt, and plenty of water and herbal infusions. 

It’s different from intermittent fasting, which restricts your food intake in a given day to 8 hours or less. Other forms of fasting include the 6:1 or the 5:2 fasting methods, in which you limit your food intake to 500–700 kcal per day for 1 or 2 days per week, and eat as usual during the other days. Another version is the alternate-day fasting, where you switch between a day of eating as usual and a fasting day for up to 1 month.

What happens in the body during fasting?

Fasting periods lasting 72 hours or more have interesting physiological effects on the body. After 3-5 days, the body switches to using ketones as the main fuel source, instead of glycogen reserves. Ketones are mostly produced from fat. On top, the body produces a small amount of glucose itself, in a process called gluconeogenesis.

Also, fasting for more than a few days kickstarts autophagy, which is the breakdown of old cell structures or misfolded proteins in order to recycle their components for fuel. It’s a bit like a deep-clean within our cells and a current hot topic in longevity research.

Why follow such a strict fast?

The main reason I decided to go on a fast was to gain more mental mindfulness and to unwind from daily stress. There was also another reason: in my latest Aware Long Term Health check, I noticed I had a slightly elevated HOMA-IR index, which measures insulin sensitivity, and had high LDL.

Everybody on the retreat had their own unique reasons for fasting. Some had received a recent diagnosis with type II diabetes, and wanted to explore the impact of fasting on their blood sugar levels. The process helped them realize the control they had over the pace and course of the condition through lifestyle modifications.

There is some debate on the exact health benefits of fasting, and much of the research has been limited to intermittent fasting. However, some research has indicated that fasting can be a tool for managing metabolic and cardiovascular risk factors, including lowering inflammation, improving insulin sensitivity, countering elevated triglycerides and LDL or “bad” cholesterol, and reducing blood pressure. There is also some evidence of benefit for people with autoimmune conditions such as rheumatoid arthritis and recent research suggests that intermittent or longer fasting periods may be linked to longevity. On the other hand, prolonged fasting has been linked to symptoms including increased risk of developing gallstones and low sodium levels.

How were your energy levels?

My second day was the most challenging. Once my body had used up most of its glycogen stores, it went into a “dip” (or “hitting the wall”). When I woke up, it took me quite a while to start the day. Some orange juice in the morning helped restore my energy levels. It’s impressive how 3 slices of orange can make such a difference.

After about 4 days, my energy levels reached a constant high. I got into a routine of swimming and hiking to keep active and prevent excessive muscle loss.

A week into the fast, I went on a day-long hike up a local mountain with 1200 meters elevation. That’s when I fully realized how well my body was able to adapt to fasting.

Will fasting help lose body weight?

While fasting can be a potent kickstarter, it is not a sustainable weight loss strategy. Ideally, weight loss should happen in conjunction with a gradual retraining of dietary and lifestyle choices over a longer time.

How did fasting impact your biomarkers?

Before fasting, my LDL cholesterol and my HOMA-IR were out of range. HOMA-IR is an estimate for your insulin sensitivity, or how well your body is able to metabolize blood sugar. 

Although still debated, some studies have shown that fasting, especially intermittent fasting, is an effective way to improve the body’s insulin sensitivity. In my case, both my HOMA-IR and LDL levels were back in the expected range after my fast, and my fasting insulin levels decreased by 25%. Moreover, my ApoB levels went from the expected range to the optimal range, decreasing by 20%. Lower ApoB levels signal healthy amounts of LDL cholesterol and a lower risk for developing heart disease later in life. The impact of fasting on biomarkers depends on many factors and differs between each person.

Final thoughts

In many ancient rites and religions, abstaining from food was meant to nudge you closer to the divine. What about non-religious fasting? What am I being nudged towards when I turn my back on soirées of wine and mezzes? Was a 14-day long denial of freshly-baked sourdough topped with apricot jam the only way to manage my untamable appetite? What about my yearning for pizza and overnight-cooked ragù? And yes, I also enjoy the vegan versions.

Since returning, I take much more time when eating. I cook better, eat less, and I don't snack. I avoid processed carbs, and the occasional postmeal brain-fog has not resurfaced. I am more active, energetic, and work out more. Take me to your favorite Szechuan pulled noodle place, and I will still share a meal with you. Only I’ll order the smaller size instead of indulging in the larger one. 

Fasting has led me to a renewed consciousness about when and what I choose to eat. I was able to de-stress, focus on myself, and get to know other people along the way. I love Anthony Bourdain’s quote (his books served as my guilty substitute for the food I renounced): “You learn a lot about someone when you share a meal together.” I might add: you learn a lot about someone and yourself when you fast together.

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