You can lose weight with prolonged fasting, but it is not the best approach. If you can lose weight with other strategies then do it. Long fasting has the bad effect of losing a lot of muscle along with the fat. It can be a big problem especially when you get older. 
What to do instead, try body recomposition:
- Low caloric density food.
- Eat a lot of protein. Think as high as 2g/kg of your mass. (1g/lb)
- Calorie counting.
- Strength training.
- Intermittent fasting.
Even if you go with fasting you will need some strategy to keep your gains and rebuild muscles when you're done. So let me start with this.
Body Recomposition #
Caloric Density of Food #
Search for Caloric Density of Food chart and look for things you usually eat.
It turns out that you can eat a lot of vegetables and feel full while restricting calories.
This is easy to miss especially on Vegan or Vegetarian diets.
You should try to reach 2g/kg of your weight (1g/lb).
The science of nutrition is complicated, but it's to give you an idea.
- Protein helps with building and maintaining muscle.
- Protein is filling.
It may be worth it to buy protein isolate powder. I can recommend ones from soy as they are vegan and will be easier on your stomach.
I can recommend The Vegan Gym YouTube Channel to learn more.
Calorie counting #
If it works for you then it will be the ultimate solution.
In my case, I still struggle with this, but something that helps me is checking the caloric density of what I'm eating.
For example - I like strawberries and bananas, but it turns out that one of them has almost half of the calories in 100g. Now I know I should prefer strawberries.
Eating a salad may not be great for your weight loss if you add a lot of oil to it. Even a spoon can have hundreds of calories.
Strength training #
If you have more muscles then you burn more calories to move them and to sustain them. Muscles help in your everyday life as well.
I'm not sure about other types of exercise. Almost any time is healthy and it's better to exercise than not, so I'm only trying to emphasize that you should add some kind of strength training every week.
Intermittent Fasting #
If you can stick to a 6 or 8-hour window then it may help you reduce your calories as well.
The protocol I was doing:
- Fast Monday-Wednesday
- Slowly introduce food from Thursday.
- Eat until Sunday evening.
I've been doing it almost every week from May until October 2023 and lost around 15 kilograms (33lb).
Most weeks I was fasting for 3 days, but if there was an opportunity or need I changed it to 2 or 4 days fasts a couple of times.
Now I'm slowly moving into the maintenance phase. I got close enough to the weight I want to keep and I'm trying to lean more on the strategies I mentioned above to help me from gaining it all back.
But, I still plan to fast from time to time. If I could lose my extra fat without fasting then I would. It's the best weight loss strategy I've found for myself so far.
Some things to expect #
- You will feel tired.
- You may feel cold. Especially when you get to lower body fat percentages.
- Lightheadedness, especially when standing fast. You need electrolytes, especially sodium.
- Meeting with friends and family can be weird when you're not eating.
- Your sense of smell will get superhuman. Really. You will smell a lot of nice things you could eat.
- The first days of a fast are the hardest. After a couple of days (3-4) you should move into ketosis and stop feeling hungry.
- You can't eat whatever you want when breaking a fast. It can be dangerous to suddenly eat a lot. Remember to start really slowly.
Some tips #
- Walking - exercise you can do even when extremely tired. It may sound simple, but try walking as much as you can. If you do more than 10k then it will be a lot of extra calories and stimulus for your body to keep the muscles you have.
- You can supplement L-Carnitine. May give you more energy and help you burn more fat.
- Coffee - can help with energy levels and will raise your body temperature.
- Drink electrolytes. At least a little bit of sodium every day. Especially when you start feeling lightheaded.
- When you break your fast try treating it as an additional day of extending your fast. Eat small portions.
- It's a big stress for your Gut microbiota, probably similar to antibiotics. Think of some probiotics when breaking a fast just like you would after taking antibiotics. It can help a lot.
- It may be a good idea to supplement with multivitamins. If you're restricting your food a lot then it may be hard to keep all your vitamins and micronutrients in check.
I can recommend watching:
- He Fasted for 54 Days: Here's What Happened. | Physionic
- The Consequences of a 50+ Day Water Fast, Explained. | Physionic
- Maintaining Weight Loss after 50+ Days Water Fasting. | Physionic
If everything else fails then fasting can be a good strategy for restricting calories and losing weight. Especially if you use that time to learn how to prevent yourself from gaining it all back.
Why Longevity Doctor Peter Attia Has Changed His Mind About Fasting | BY SYDNEY BUECKERT, NASM CPT, CES, FNS, GPT ↩︎
How to Build a Meal for VEGAN Weight Loss - (Plate Breakdown) | The Vegan Gym ↩︎
THE BEST VEGAN FOODS FOR FAT LOSS ↩︎
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