Pros and cons of Intermittent Fasting

Publicado: 26/10/2010 en nutrition, Paleo/Primal

In case you have no idea what Intermittent Fasting (IF) is, here’s a little remainder: there’s quite few ways to do it, but basically you fast for 16 hours – that includes the time you spent sleeping – and eat your meals in the 8 hours window you got left.

For example, you skip breakfast and lunch and start eating at 4 PM. Here you can go in two different ways: eat ALL your calories for the day (and that’s a lot of om nom nom’s, you can do this daily) until 12 AM; or just eat what you normally eat after 4 PM, resulting in a calorie deficit (just don’t do it every day, the “Eat Stop Eat” approach says do it 2 days per week).

So why on Earth would someone eat in this hippie way? Well..


– Insulin is kept at minimum during your fasted hours, resulting in the use of your body fat for energy. Insulin is highly anabolic (meaning “anabolic” as taking the chemical energy from food and transforming it into real tissue), so fat burning is impaired as long as insulin is high.

– You give your pancreas a rest during your fasting hours. This might be of extreme importance for diabetic people… Go check that link, insulin-dependent dude goes paleo and IF and keeps his diabetes without medication now. Interesting read!

– Insulin sensitivity goes high. That means that when you do eat, your pancreas need to work less to do the same job.

– Growth Hormone (HGH) goes high during the fasted state. This hormone helps to repair your body and build muscles. When 4 PM arrives, and you eat again, your body is on “give me the bricks to build muscles faster” mode on.

– During a fasted state, your sympathetic innervation gets more stimuli. Fat cells have that innervation. Do the math.

– Since all the blood that used to be in the digestive tract now has a break, circulation increases in other tissues. One reason why stubborn fat is stubborn, is its poor vascularity. Now you are able to take fatty acids away from those cells and into the bloodstream.

– And muscle tissue is spared during the fast (for more than 48 hours actually), provided that you are involved into some kind of resistance training regularly. If you don’t lift weights, I don’t know what happens. But still, we’re talking just 16 hours here.

OK, enough with boring biology. Plus, this guy explains it much better in this article than me and knows a lot more about it anyway. But there are some practical pros as well:

– I love to cook. But I don’t like to cook after I hit the gym, had dinner and all I want is to hit the hay. The day is over and you just want to chill or sleep or whatever, but you still need to cook your lunch and pack it, maybe breakfast too and pack it if you are like me, because if you don’t cook ahead you end up eating vending machine crap at work.

Doing IF I don’t need to cook or plan anymore. I won like 1 hour of time everyday.

– You get to eat lots of stuff that are banned in the “normal” way of eating. 5 strips of bacon and 4 whole eggs with 2 cups of whole, full fat milk and coffe for breakfast? No way, José, unless the breakfast is at 4 PM. You actually try to add more calories (as in extra bacon) just to meet you calories for the day.

– Also, you get to experience full, and I mean FULL errr… fullness. Like you binged big time, but when it comes down to calorie counting… you still need another 500 cal snack just to hit maintenance calories!

– Oh, and I use my lunch hour to take a full hour power nap at work =D

OK, OK, too good to be true. Everything that has a good, shiny side has a dark, evil side as well. Here are the cons from my point of view:


– You do get hungry while fasting. You miss lunch. You try to keep ocuppied or fool the guts with green tea and coffee and the like. It usually works like a charm, but sometimes it doesn’t. You’re never in real hunger pain, but it bites.

– It’s really hard to eat all your calories in just a few meals. There you have this yummy, high calorie, zero guilt feast in your plate but when you reach fullness, you still have like half your plate to eat. And you must force it down your throath. They say you get used to it and eventually like it. It’s getting easier for me, but I still struggle.

– I stopped eating lots of veggies and fruits. You just reach for high calorie density foods, so you can meet your target calories. I can’t afford to get full on spinach and not eating all the other stuff.

– You look great in the morning. Pants almost falls off if you don’t use a belt. You look thinner, and you have a smaller waist all day long… until you eat. Since you eat a lot of food in one sitting, I swear you go up one size of jeans automatically. You need to unbutton your pants after the “breakfast”. Be warned, do not look at yourself in the mirror just to check on your “abs” after eating. After my meals, I look PREGNANT LOL. Sure, it comes down about an hour after but still…

So there you have it. Just another piece of info you can use (or not) while trying to make this puzzle all toghether. I’m not saying this is the only way that works. It’s just A WAY that’s is getting pretty popular right now, is based on science, and worth a shot. Maybe you might wanna skip breakfast and lunch if you have a fancy dinner in this Italian restaurant, or maybe start eating at 4PM if you know you’re gonna go out and have quite a few drinks. Or have some peace of mind when life get in the way and you skip a few meals and you go all nuts because you didn’t eat your proteinz and aminoz and teh bicepz are going all catabowlik. As everything in life, take it with a grain of salt =D

  1. Top post mate.
    I use it as a weight-loss tool and to use during holiday periods when you are eating/drinking more of the wrong types of things.
    For building mass, I’m not sure its advisable. Like all things though, mixing it up and cycling is the way to go.

  2. Dawn dice:

    Interesting concept. I can see that it would be difficult to take in enough calories in only one meal. Not sure that it would suit me because I love my fruit and would find that very difficult to give up.

    Possibly one to try on isolated occasions when it fits into a person’s schedule. There are days when it would just be easier to forget about a couple of meals!

    Enjoyed getting such a balanced explanation of the pros and cons of intermittent fasting.

  3. David dice:

    This was a good read. I’ve been curious about the fasting approach. Might use it when it’s time to lean out before summer. 2 days a week… I could probably pull that off. Thanks!

  4. Primal Toad dice:

    This was an interesting read! I am just beginning to experiment with small window eating.

  5. Gary dice:

    After starting IF for a few weeks now, I agree with you on the looking super bloated after breaking a fast. My 2-3 meals during my feeing window really makes my stomach quite round.


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