Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
30 Dec

Fasting Makes You Active

It’s a familiar image we might attribute to stereotype: a sluggish, maybe portly individual lying prostrate on the couch, his/her front littered with Dorito crumbs. Could there, however, be truth behind the picture? Is there indeed a connection between incessant snacking and chronic slothdom? Or considered another way, is there a connection between fasting and being active? As a long-time fan of intermittent fasting (and a believer in the research behind it), I’m convinced. A study out this month sheds even more light on the relationship between lethargy and continuous eating.

For decades now, conventional wisdom has told us that we should eat regularly throughout the day to keep our blood sugar steady. With three regular meals and at least two snacks, we’re counseled to keep our bodies in a perpetual postprandial state. However, newer research, including this month’s study from ETH Zurich, questions this assumption. Scientists focused on the opposing relationship between a transcription factor, Foxa2, and insulin. Foxa2 is found in both the liver and the hypothalamus, the central command for hunger regulation. It has a hand in the expression of two eating and physical activity related neuropeptides, melanin-concentrating hormone (MCH) and orexin. When insulin is present, as it is during and after eating, Foxa2 and the related MCH and orexin are reduced. However, fasting mice showed consistently high levels of Foxa2, MCH and orexin. The researchers then found that “hyperinsulinemic, obese” mice showed reduced Foxa2, MCH, and orexin, regardless of whether they had eaten or not. When the scientists bred mice with continually active Foxa2 (immune to the counter effect of insulin), these mice showed high levels of MCH and orexin – and a correspondingly high level of physical activity whether they had eaten or not. The specially bred mice had low body fat as well as higher muscle mass.

Consider this study another nail in the coffin of conventional wisdom. (It also goes a long way in explaining the snacking couch potato association.) Fasting, even short, between-meal breaks, promotes the activation of Foxa2 and the resulting formation of MCH and orexin – as well as their activity-inducing effects. A simple survival principle explains this: a hungry animal needs to get up and move to find food. On the other hand, if we are constantly swimming in the insulin of eating and post-eating states, we’re undermining our own motivation (and biochemical stimulus) to get up and burn off what we just ate.

CW encourages us to never skip breakfast, bring along a mid-morning snack, make time for a good lunch, grab a mid-afternoon nibble and then have a good dinner. Oh, and if you can’t sleep, you’re supposed to have warm milk and a banana before bed. Our bodies are either eating or processing what we ate. There’s never a recovery period. Nary a resetting opportunity. We’re so focused on the hobby horse of “stable” blood sugar that we’ve forgotten that there’s more to the biochemical story of balanced energy. We make ourselves feel perpetually full to the exclusion of feeling anything else. (How about light, energized?) We continually raise our blood sugar and insulin levels and, in doing so, turn off the body’s chance to activate or upregulate other key substances that promote energy balance – and as this study shows, the physiological motivation to be active. Simple advice: skip the snack. (Besides, dinner never tasted so good as it does on a healthily empty stomach.)

Let me know your thoughts. IFers – have you found this principle to be apparent in your own experiments? Thanks for reading.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Hi, I’m new to IF – going on my 2nd week. I do struggle with hunger occasionaly, but I find when I drink water with a splash of lemon and a dash of cayenne pepper (for kick), I’m good until my window at 5:00. I feel incredible! So in control, and knowing that I am no longer controle by food. This is the longest I’ve stayed on a “diet”. I still have to incorporate better food into my diet, right now I’m eating pretty much what I want, but I know this has to change in order to be at my optimum health, and not to mention my ideal weight. I have about 73 lbs. to loose to be at my desired weight. So far I have lost 6 lbs. and I truly believe this time, with IF, I will reach my goal. So glad to have found this site! If anyone would like to “buddy-up”…I’m all for the support and encouragement!

    Joyce wrote on February 27th, 2011
  2. Now THIS explains why Jack Bauer can go 24 hours without eating! If he DID eat, he wouldn’t be able to go 24 hours at all!

    Flitcraft wrote on March 9th, 2011
  3. Just started training at Crossfit about a month ago, and trying to get used to this whole Paleo/Primal thing. I fasted for the first time in my life yesterday, went 20(ish) hours, worked all day just drinking water and even golfed after work and felt fine.


    Here’s my issue: Say for example my in-laws are having us over for dinner and they’re serving lasagna, I’m not going to be one of those a-holes and say, “Nope, sorry, not apart of my diet, won’t eat it…” I’m going to be polite and eat what is being served. Primal is good in theory, but when you’re eating as a family, it really hinders you (or your family).

    So what do you do when the family is eating something “non-primal”? Anyone else running into these very real problems?

    I can get away with the primal thing for breakfast, no one takes offense if you don’t eat pancakes or waffles.

    But when it’s a family meal/dinner, how do you say no?

    Sammy wrote on March 24th, 2011
  4. I came across fasting while working as a weekend security guard. The security handbook manual, specifically mentioned that guards on duty, must not eat or drink anything. Since I was working a full weekend shift…that meant 48 hrs. of a complete abstinence fast. What I found, was that my mind became very clear and alert, and was able to respond to any emergencies quite effectively. Going without food for a few days is a small price to pay, considering the enormous physical and mental benefits resulting from such a dietary practice.

    Ernest Zak wrote on March 25th, 2011
  5. I’d have no problem telling family, hey guys, I trying a new way of eating, please don’t be offended if I don’t have the lasagne. Eat their salad and use the opportunity to tell them how much weight you’ve lost/healthier you feel/etc etc.

    If family don’t understand then my gosh you are in a bad way.

    If you eat it then suggest an after dinner stroll to deal with SOME of the pasta?

    Ive been known to pick out the pasta in a dish and simply say Im sorry I dont eat pasta anymore.

    They might surprise you and ask why!

    Makes for interesting dinner conversation!


    Jane wrote on July 12th, 2011
  6. I’ve been trying to read all the posts connected to IFing (love saying IFing–smile). And I have to tell ya, Ifing is amazing for energy for me. I’ve posted earlier, I fast Monday, Tuesday, eat Wednesday, and fast Thursday. Three days of water/week. Tuesday is by far my best day of energy, sleep is incredible on Tuesday night, Wednesday morning I don’t want to ruin by IFing buzz, but I do by noon. I eat pretty normal on Friday through the weekend, you know–beer the whole bit. I have to tell you, I’m really considering going total health nut diet during the weekend, I hate that I ruin my f-ing buzz by eating and drinking– yet, I still am tied to to the sociology of “going out– havin a good time”. It’s just that I’ve never felt this good. Maybe I’ll become a non-drinker…

    mory wrote on July 31st, 2011
  7. I began fasting about 3 years ago. I eat once or twice a day although I do take in calories while fasting. These calories are in the form of fats that in my opinion supports the ketogenic aspect of fasting. My diet is strictly low carb which also supports the ketogenic aspects. I am pre-diabetic and I keep my fasting glucose levels under 100. That being said, I can keep my fasting glucose levels under 90 with little effort.Supplements I take are ionic magnesium, vitamin D3, krill oil. If what “they” say is true, regarding the need to eat constantly throughout the day,there would be no way I could eat this way. I plan on going a day or two without eating to increase my fasting window.

    Mary Titus wrote on August 7th, 2011

Leave a Reply

If you'd like to add an avatar to all of your comments click here!

© 2016 Mark's Daily Apple

Subscribe to the Newsletter and Get a Free Copy
of Mark Sisson's Fitness eBook and more!