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Fat Adapted Athlete

Updated: Mar 14, 2022

Human body mainly stores energy in form of fat, so that it can use when necessity arise. I was interested in understanding when I have so much of fat in in our body (mine is 23% close to 15 Kgs), why do I still hit a wall when running a marathon? All the research journals, and experts confirm that no energy system works in isolation. Body always burns both glycogen and fat together for energy. Why is that when I talk about being "fat adapted", everyone points towards Keto and glycogen depletion? My experiments are more towards exploring options for utilizing fat for energy MORE efficiently along with glycogen as opposed to being in "Ketosis" and relay only on fat as energy source.

Note: This is purely an experiment and putting my limited knowledge on human physiology, anatomy and nutrition knowledge.

How to tell/train my body to use fat for fuel? The idea is to deplete carb/glycogen storage in our body and "force" it to use the body fat for energy, the actual purpose we have the fat reserve.

People use different approaches to achieve this

  1. Low carb diets, like Ketogenic, Paleo

  2. Intermittent Fasting (IF)

I choose IF route as the stress of restricting, low carb vegetarian meal was too much for me to handle and as mentioned above, I'm more interested in "maximizing" fat utilization rather than using it as "only" source.

Many say they’ve gotten healthier and leaner, faster, by deliberately skipping meals and sometimes going entire days without eating.

The IF research is intriguing, but young. Some animal and human studies suggest that IF may have benefits, but we don’t have enough long-term data to know for sure. Me being me, wanted to experiment with IF and checkout the intricacies of IF.

Let me try and summarize on my IF journey till today

"Fasted" workout

Eating a banana, some dates or atleast 2-3 biscuts before my workouts/run was a mandatory thing for me. First thing I started was to try and skip that food before the workout. It was easy for me to adjust to the short intervals and strength training as the duration was typically 60-90 mins. But long runs were a bit of challenge. There were couple of runs that I aborted and stopped in the middle because I developed headache. But as any change, the crucks lies in incremental approach. Slowly after couple of long runs, I was comfortable running doing my long runs with around 10-12 hours fast (I generally have my dinner around 8 - 8:30 pm. Main thing we need to keep in mind is that any food we eat (unless it is highly processed gels) it takes easily around 30-60 mins before we digest and get energy out of it. So whatever we eat first thing in the morning before workouts hardly has any impact on our workouts.

Infact, I recently read a research where it is actually counter productive!!! Our pancreas releases insulin in response of any carbohydrate we eat. Insulin being an anabolic hormone, actually inhibits fat oxidation, means our body doesn't use fatty acids for energy during workout, if we consume pre-workout carbs!!!

I continued this for 3-4 weeks

Intermittent Fasting

By now I was pretty much convinced that hunger doesn't have any direct relation with my energy levels. Then I decided to experiment on IF. First thing I tried was to extend the over night fasting by couple of hours, by eating my dinner early. So I started having my dinner 2 hours early around 6 - 6:30 pm. But with my daily routine and work schedule, I found it difficult to manage as most of the days I found myself outside home at that time. Extending on the otherside and skipping/delaying the breakfast was not an option because of the intensity of the workouts I do. It is important for me to feed immediately after the workout. Though I was comfortable with 12-14 hr fasting, it was difficult for me to implement because of my schedule

Intermittent Fasting - One day a week

Then I decided to take a big leap and opt for a full day fasting. I choose Sunday, because it was my rest day. Schedule was

  • Eat moderately (little less that required) during 5 days (Monday to Friday)

  • Eat heavy almost 1.5 times on Saturday

  • Sunday complete fast (with only water and green tea)

On Sundays I kept myself pretty relaxed without much of physical activity. But obviously my body which was carb addicted, protested with stomach cramps, headaches, made me short tempered, easily irritated, sleepy, etc.

Luckily first 3 weeks, I had scheduled workshops (half a day) which kept me occupied. Stomach used to growl and remind me of hunger around my meal time. I just drank water or green tea and ignored the hunger. As fasting duration increased, evenings became little bit tougher. Having fasted for 20+ hours, I was having mild head aches and didn't have courage to venture out thinking I may not have the energy. I pretty much ended up sleeping early around 8:30 - 9 pm. Monday mornings were bit interesting and unusual. I was feeling very light and week. Had tingling sensation in my arms and legs. Generally used to break my fast with a banana and then a normal break fast after 30-40 mins. It took me around 4-5 weeks to get used to the routine. I started enjoying the fasting days, as I had more time on hand and monday mornings were more energetic

Fat Adaption

Once comfortable with full day fasting, I started exploring the idea of fasted workouts. Atleast in theory, endurance athletes are supposed to be using fat as their fuel during workout. I started doing my research on athletes who are into endurance sports and were completely dependent on fat for their activities. I was surprised to find a large community of athletes who were totally in to endurance sports (running, cycling, triathletes) who were totally killing it using their body fat at fuel, all with almost zero carbs during their 100+ mile activities. I did my first workout (strength training) at home, mainly because I was not having courage to venture out :). Intensity was low, but I could pull it off comfortably. Next week to that, I did a full intensity workout for 60 minutes which included lifting and HIIT. I enjoyed it thoroughly with absolutely no hint of fatigue. Infact I felt I recovered faster from the workout!

With that confidence I started doing my long run on sundays after fasting on saturdays. Ran (medium intensity) around the familiar territory of Kanteerava stadium and Cubbon park, to be safe and the feeling post run was amazing. Absolutely no fatigue and after 30 mins, I didn't even feel the need for recovery.

Now it is pretty much a norm for me to go on fasting for a day prior to my long runs. I'm even able to do my high intensity runs without any intake of external carb source.

I'm pretty confident that my body is able to efficiently burn the fat and use it as fuel. Planning to run/race Hyderabad Half Marathon in fasted state and without external carb. Will keep you guys posted on how it'll go

Take away

On the benefits of IF I could immediately notice,

1. I've lost 4 kg in past 2 months

2. Become fat-adapted and able to do my endurance runs without fear of hitting the wall

3. No longer worried about being low on blood glucose because of hunger; body is easily able to switch over and get its energy from fat

4. Feel a lot lighter and stronger


For anybody who is looking to practice IF,

  • Start with a small fasting window; easy approach is to extend the gap between dinner and breakfast

  • You don't have to stick to the standard 12:12 / 8:16 / 4:20 / OMAD (One meal a day). Choose the fasting window you are comfortable with and extend it by as small as 30 mins

  • Just because you are eating less during the feed window, doesn't give you license to eat junk food. Try and eat whole some, whole grain and balanced meal, which'll help you feel full for longer time

Happy FASTING!!!

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