I wonder how long it takes for what you eat to turn into fat.  Like if I eat a really big meal, HUGE, 10,000 calories, when will that fat show up?  That was one of the questions my sisters posed last week when we were talking on the phone.  I know.  Talking on the phone.  Like cavemen.  It was so retro.

I wasn’t sure if this question was hypothetical or if she was currently sitting in front of 12 Big Macs with plans to wear a non-stretch bodysuit tomorrow hanging in the balance.

I said, You mean once you eat, how long before you can’t stretch denim over your thighs anymore?  I dunno.  It takes 24 hours to digest food or something like that and I guess that’s when it would take out the calories it needs and vitamins and stuff but … I don’t know.  And what about calories?  I mean, eating fat I can understand. It’s already fat so it must just frantically grab onto something as it slides through your body and not let go.  That way it just becomes a part of another blob of fat in your body.  But calories from, say sugar, do they have to go through some sort of fat bootcamp to become fat?  I can’t believe I’ve never worried about this before.

We exhausted the discussion at that point and went on to talk about other pertinent topics of the day like whether or not stirrup pants should ever make a comeback.

But after we hung up I couldn’t stop wondering about the whole fat thing.   How long does it take for that donut to turn into a muffin top?


It’s a lot sooner than you probably think.

I did a lot of reading and a lot of researching and it made my head spin, which is good because spinning burns calories.  I’ve tried to condense everything into an easy to understand timeline on the cycle of calories and fat.


This is an incredibly basic explanation of it all.

7:00 a.m. You wake up, have a black coffee then end up working and running around the rest of the day without eating anything.

6:00 p.m. You haven’t eaten a thing so you have zero calories in you.  You scarf down a BIG meal.  A Big Mac Meal with large fries, 6 chicken McNuggets and a chocolate shake.  Mmmmm.  That’s 1850 calories.

10:00 p.m.  Your body starts storing the first 1,000 calories from that meal to use as immediate reserves  that your body can quickly access when it needs energy.   Those first 1,000 calories are stored in your liver and muscle immediately.  These are called glycogen calories.   The other 850 are extras you don’t need immediately so the body turns THOSE calories into fat cells known as triglycerides.  This all starts happening after 4 hours.

Your meal was 1850 calories.  A pound of fat is made up of 3,500 calories.  That means technically you have just stored enough calories for 1/2 pound of fat.

10:01 p.m.  You’re now freaking out because you know you just gained half a pound in 4 hours.    Calm down.  It’s only there temporarily and only part of it becomes fat.

10:02 p.m.  The first 1,000 glycogen calories of that Big Mac meal start being used immediately as energy for your body even if you don’t feel like you’re doing anything.  Your body burns those calories just to lift your arm, beat your heart, or roll over in your sleep.  In fact, just being a human being means you’re going to burn 1,000 – 1,500 calories in a day even if all you do is lay in bed.

10:15 p.m. You decide you will indeed lay in bed for the rest of your life because what’s the point.  So you’re going to burn 1,500 calories doing nothing!  Yay!  But what about those 850 calories you ate over and above what your body will naturally burn?  They have indeed already turned into fat.  1/4 of a pound.  Or 8 Tablespoons of fat.  If you don’t exercise, move more, do STUFF to get rid of those fat calories that immediately plastered themselves to your gut, they’re staying with you.  O.K.  You decide you won’t spend the rest of your days laying in bed.

8:00 a.m.  You slept all night, you get up and start the laundry going, you go for a run and mid run your 1,000 calorie reserve is gone so your body needs to go into the 850 calories it turned into fat last night.  At that moment, you start burning fat.   If you didn’t go for a run or do something that burns a lot of calories, you wouldn’t get into the phase where you burn fat cells.  Booooo.

9:30 a.m.  You eat breakfast and it all starts over again, building up your reserve of 1,000 calories.  If your breakfast is 1,000 calories that means your body will burn off those easy to get to 1,000 glycogen calories before anything else.  They’re easy access.   But if you only eat a 300 calorie breakfast, your body will burn those 300 calories and then will be forced to get its energy from those fat cell triglyceride calories that are otherwise known as ass fat.


That’s the long answer.

The short answer is your calories start the process of turning into fat as soon as 4 hours after eating them.  But it would take a couple of weeks of eating too many calories for that fat to show up in a meaningful way. In a muffin top way.   An extra 850 calories a day for two weeks without adding any exercise to your daily routine will mean at the end of 2 weeks you’ll have gained 1/4 pound of fat every day for 14 days.  In two weeks you’ve gained 3.5 pounds.  Think it’d be hard to eat an extra 850 calories every day?  That’s half of a large bag of potato chips.

And that is the story of why I can’t buy potato chips anymore.

I’m going to be spending a lot more time paying attention to the activity monitor on my Apple Watch now that I actually really understand it.  The Apple Watch and the less expensive Fitbit both count your “active calories” burned.  Those are the calories you’ve burned over and above what you’re already burning just being a living human. So if you pay attention to when you … overindulge … you can bump up your activity level the following days and easily track it on your watch.  It really does work.  I mean if you try.


O.K.  now that I have an answer to her question, I have a phone call to make.




    *sigh* what depressing news . . . Thanks for the explanation! I posted a link to this post on Facebook because I thought it was great to find an easy to understand answer to this mystery.

  2. Heidi says:

    Nice text but not entirely true. You need quite a huge amount of energy just to keep your organs working+ energy to digest the food and turn it into body heat. If you just laid down the whole day without moving or eating you’de burn at least 1200-1500 calories a day(including night when your brain is doing hard work to process all the information you got and growth hormones repairing/making muscles stronger etc) +digesting protein consumes energy 30% of the amount of calories you get from protein(and from a big mac beef and chicken meat you get lots of it). Digesting carbs consumes energy about 4%, fat 0%. And body stores carbs about 2000kcal to liver and muscles. There wouldn’t be left enough calories to turn to body fat. Our body is a complex system.

    • Karen says:

      Yes, the post says most of that.  “The first 1,000 glycogen calories of that Big Mac meal start being used immediately as energy for your body even if you don’t feel like you’re doing anything.  Your body burns those calories just to lift your arm, beat your heart, or roll over in your sleep.  In fact, just being a human being means you’re going to burn 1,000 – 1,500 calories in a day even if all you do is lay in bed.” My goal was to make the text digestible (ha!) and understandable for the average person wondering about how long it takes to turn a calorie into fat. ~ karen!

  3. Rachelle says:

    After trying to get an answer to this with other resources, you made this really easy to understand!

  4. Melissa Keyser says:

    The answer to the stirrup pants is no. They should not. But I’m sure whoever keeps trying to force harem pants on us will try that as well.

  5. Kathy C says:

    Let me just say, I miss stirrup pants. :-)

  6. Maureen says:

    A related question. How can I weigh first thing in the morning, then go to the gym, come home, weigh again and be heavier? That seems impossible.

  7. Lisa Dart says:

    So red wine is still okay! Happy Dance – well it is good for you. :-)

  8. Magali says:

    Years ago I managed to gain 8 pounds in two weeks in France. Despite all the walking from being a tourist I ate way too many crêpes and crème brûlées! I’m still impressed that I managed to do that!

  9. Benjamin says:

    Screw it, Ima have a pasta donut with Nutella and maple syrup right now before bed. HAHAHA…

  10. Robyn says:

    I don’t think stirrup pants should make a comeback. That, and I ate an entire peanut buster parfait on Sunday.

  11. After my week of indulging on a super yacht in Komodo, I was wondering this exact thing too. Literally. True story.

    I probably deserve it after mentioning ‘super yacht’

    Oh, did I tell you about the time I spent a week on a luxury super yacht in Komodo?

  12. Noelle says:

    Oh you “sugar burners” have so much to worry about. If you like nutritional research look into nutritional ketosis and intermittent fasting and a fun phenomenon called autophagy.
    It’s an advanced way of eating/ not eating that I use to control my diabetes (thanks chemo, you’re an asshole). You could do the occasional short fast and still eat potato chips. I on the other hand can’t really eat anything but cabbage and steak, which is why I’m just generally crabby. ;)

  13. Christina B says:

    Just an alternative to the expensive tech gadgets, I got a Xiaomi MiBand 2 from & I love it. I wasn’t sure how much I’d track but I really get quite a bit of use from it, and it’s only $30 usd. Also found out my Apple Health app on my phone has been automatically tracking my steps & activity (you just have to enable it in the settings) so the tracking band is an extra reminder to get up & move, or take your heart rate if you’re into that.

  14. kelli says:


    I’m trying so hard to steer clear of wheat* and sugar and you show me a big stinkin gloopy yummy delicious donut.

    Sheesh…if you can’t trust your friends who can you trust???

    *Wheat bad:

    • Leticia says:

      Oh, Kelli.

      I don’t subscribe to the demonization of foods. Nor do I subscribe to science done the way this doctor is reporting. “I noticed a pattern”, he says. Science requires a study: Two groups, one avoids wheat, the other doesn’t. Measurements and blood tests are done in the beginning and the end of the study, also along the way, funding allowing. The larger and more varied the groups, the more relevant the results will be. Try and control for different things than wheat in the diet that could affect the results: everything, from disease, to lifestyle, to the rest of the diet. Other scientists do the same study and try to get the same results. If any of those results aren’t what they expected, there is probably something else at play and it should be investigated. Such a cruel mistress is science.

      Has he done that? No. Are those kinds of studies reliable? No. There are too many variables in the diet, genetics and lifestyle to account for, they are expensive, should be long term and there is not a lot of funding for this.

      I would never, ever banish a food from my diet based on pseudo science. Wheat bread, as made by large companies, is probably not the best thing. Wheat berries, that are just the whole wheat, unprocessed, aren’t the devil. If you can make your own whole wheat bread it will be much better than store bought, by the way. Besides, doughnuts are delicious and I will have them when I can get some. :)

      • kelli says:

        Thanks Leticia, I appreciate you. While I believe in moderation (hard enough to do!) I’ve read enough and learned enough to know that over the past 30-40 years, processed/GMO/bad foods have increased, and health overall has decreased. This is fact. Now I love me a donut as much as anyone, but I choose to steer clear because there are better substitutes out there. Blessings!

  15. karin sorensen says:

    i was always curious about that, but could never be bothered to look it up.

    enter: Karen! awesome info!!!!!

    I’m of the tribe of homo sapiens that eats a little during the day and wolfs down half a village at night. 10 years ago I got away with that, these days not so much. meh, it could be worse. besides I’m pretty proud of my grocery basket, almost no packaged stuff, ever. our philosophy is if it comes from a box, it’s properly not that good for ya.

    thanks Karen, for yet again providing content I can use in my simple little happy life.

    have a great week.


  16. Kathy says:

    I’ve had my Striiv for 3 years. It clips on waistband or in pocket (a fitbit on wrist gives credit for sitting and moving arms) it tracks steps, calories, stairs, miles and time expended. It will issue a challenge, give points to build on fantasy land, and award animals like tigers that roar and turtles that go into their shells. The stats are weekly and monthly. I wear it every day. And I love the calorie info, that took alot of research and then translation into muffin tops. Yeah You.

  17. Linda in Illinois says:

    oh man, I just ate 4 rolo’s now I have to figure how much stuff I have to do to get rid of that ass fat.. seems like no matter what I do (short of a work out nut, I’m 60 after all) doesn’t get rid of that ass fat on me, (but I can attribute some of that to genetics). That’s my excuse and I’m sticking with it. lol. Thanks Karen, glad you taught us the facts. I always wondered.

  18. teri says:

    I ate chips while I read the comments and had no guilt. really! Mind you, I likely gained a pound…. HA!

  19. This is the best thing I’ve read all month! I’m actually studying this and cellular respiration right now in biology and have a test over it tomorrow. I’m sharing this with my class as a little pre-test humor! Thanks for the info and the laugh!

  20. Shelagh says:

    when you don’t eat all day your body goes into survival mode and stores as much as it can as soon as you eat anything…
    Solution eat 6 meals a day of smaller amounts with a little bit of protein in every meal. Never go hungry and lose weight.
    Of course I’m one of those folks who actually prefers steak and veg to chips and cake. Now if only I could cut down on my wine….I might actually lose a few pounds.

  21. Jenny says:

    I am now suddenly regretting having ice cream for dinner last night.

  22. Mary W says:

    Pinned it. VERY interesting, indeed. Kinda threw that into my face, didn’t you? I just hope it sticks into my brain. Speaking of donuts, I just found a quick and easy way to make sprinkles that I WAS going to try. Not that they are big fat producers but what I would put them on is. Oh well, back to my just learned fast, easy bread making. No knead is definitely not no need. Maybe you should investigate the science of how the smell of baked bread (or even popcorn) can make you shove a half loaf (covered with butter) into your mouth within 5 minutes of taking it from the oven.

  23. Jenifer says:

    Did you know that you can GAIN 20 pounds in one year?? Apparently there is something in the wine here…

  24. jaine kunst says:

    Ummm, OK I’m going to eat that leftover apple fritter for breakfast anyway. You can’t stop me with all this technical stuff.

  25. Catherine Vosper says:

    Interesting and easily understood info….not to mention entertaining, well done!

  26. TucsonPatty says:

    So those 4 large helpings of pasta salad last night are the reason my pants do not fit today! Oh, that might also be bloat from the never empty stomach! Party last night with lots of starches and I ate multiple helpings! Mashed potatoes, baked beans, macaroni salad, and cornbread! (Other peeps also had BBQ shredded pork) it was a million calories, and I won’t be doing that again. Soon. Maybe my Pringles aren’t quite that many calories. Oh my. Thanks Karen. Really truely. I might slow down, now.

  27. Chris White says:

    This is so awesome! Thanks Karen. Well, except for ruining potato chips for me for ever. Because, let’s be honest, I am not going running to make up for being naughty. I’m more likely to try to make myself feel better by chasing the chips with a chocolate bar…..

  28. Jenny W says:

    Thank you – really :) Timely for me, and very well explained.

  29. Leticia says:

    That’s the simple answer, actually, because the body processes different foods at different rates and in different ways.

    So 2000 calories of lettuce (good luck chomping that mountain down – a head of lettuce is about 7 calories) will be processed much slower, take a lot longer to go through and take a lot more effort from your body to process. 2000 calories of lard are a much smaller volume and are processed much faster. Even worse are 2000 calories of sugar, that start to be digested on the mouth, not in the stomach or the intestines.

    This is the part of the equation that impacts the satiety quotient. When you eat something that takes longer to be digested – whole foods, leafs, the combination of protein and carbohydrates, you feel fuller longer. That reduces the chances of overeating.

    I’ve been cooking for myself at home these days – it’s both fun and boring – and I have been making big batches of stew. Last batch was meat, wheat berries and pumpkin. This week is going to be meat, the last of the wheat berries and yams. Next week probably chicken, whole grain rice and some other vegetable I feel like. Then I reheat it twice a day until it’s gone. I avoid eating too much chicken here, since they are factory raised (hormones and antibiotics) and the cattle is still raised on open fields, different market forces in Brazil.

    • Teri says:

      Your comments, along with those of ‘Shelagh’ are all part of the equation. Thank you. Taken all-in makes understanding why those mixed nuts I’m in love with are just as well taped directly to my thighs.

      • Jan in Waterdown says:

        Yeah Teri, but you can’t taste them taped to your thighs like that. And it’s all about the taste right?!

  30. I just ate 80g of dark chocolate while reading that. Did you know that dark chocolate is really good for you? Make that 100g. Some deep thinking happening right now, burning lots of energy.

  31. Katelyn says:

    Karen you are amazing. Your content is amazing. I’ve been reading your blog for years and never given you a cent and you deserve many cents. Even dollars. My dollars. But all the bouncy ads on your site drive me bonkers. Could you put on a button or tip jar so I could pay you dollars directly and not see the ads anymore? No begrudging here, just trying to avoid bouncy-ad induced seizures.

    • Iris says:

      Hi, I totally agree with Katelyn above, I’ve long been a fan but the bouncy ads really spoil it for me such that I only occasionally look in. Also, I feel it’s made it a little bit less trustworthy for me. Sorry Karen, I don’t mean to offend you. Iris

      • Karen says:

        Hi Iris, I’m not sure how ads make a blog feel untrustworthy to you, but it’s the way it is I’m afraid. A blog with no ads means it’s a hobby blog. A blog with ads means its how someone makes a living. I can’t get rid of them any more than a magazine can get rid of running ads, or a television show or a radio program. :) You can trust me and my site but other than telling you that there’s not much I can do. :/ ~ karen!

        • Iris says:

          How nice of you to reply – this is why we all love you. I get the ads, it’s just they seem more intrusive of late? And whilst you always advise if you are commercially invested in products you recommend it does just raise a question. But I shouldn’t have said untrustworthy because you aren’t. Now I’ve got myself into quite a mess, clearly I shouldn’t be posting anything in the mania and despair of insomnia xxx

        • Karen says:

          Ha! Don’t worry about it. :) ~ karen!

  32. Kelly says:

    Crap. Had to read this AFTER I had a piece of cake. Thanks, Karen!

  33. Gayle M says:

    Dang it, Karen! No excuse not to walk (vs drive) that half mile down into the village for a soft serve anymore! I’ll always be thinking of you when food temptation strikes. And…that’s not such a bad thing at all! Thanks for the inspiration.

  34. Marie Anne says:

    Cool! I’ve pondered that exact question! Thanks 😊

  35. Kate says:

    You know on top of everything else you must be psychic. This is a question I’ve been pondering hard for the last few days but had no idea where to find the answer to. Obviously I shouldn’t have worried. It was going to arrive in my inbox courtesy of your awesomeness. Sadly it means I’ve developed an instant aversion to chips.

Leave a Reply

Your email address will not be published. Required fields are marked *

The Art of Doing Stuff