How to lose 10lbs in 10 days

[Disclaimer: It is sad I need one, but obviously people can’t read. This post is a mathematical example of how practicallyΒ  impossible and unsafe it is to lose 10lbs of pure fat in 10 days. Read what I wrote before you leave your comments.]

I wanted to give you some food for thought the next time you pass by a news stand and it makes the claim “lose 10lbs in 10 days!”

An estimated 60 to 85% of white adipose tissue’s weight is lipid, with 90-99% being triglyceride. The remaining weight is water and a slight amount of protein. The weight of 1lbs of stored lipid is roughly 400 grams. If we know through other calculations that fat energy is 9/kcal per gram then it’s time to do a little math.

9×400 = 3,600 Calories (general round figure is 3500 calories per pound of fat)

No matter what you believe from carbphobia to fat hate, you can’t dispute the amount of energy in stored fat. To remove that energy, you have to be in a deficit of that caloric amount (actually more) in order to remove a pound of fat. Since there is no way in ensure 100% energy consumption in fat, this would take more energy expenditure than 3,500.

In order to remove 10lbs of pure fat in 10 days, it would take an excess of 35,000 calories. To give you some perspective on the severity of that, here are a few more numbers.

Sex – Female
Weight – 155lbs
Height – 5’5
Activity Level (including general training) – 1.5
BMR + Activity – 2,300 calories burn per day, with general exercise

As you can see in this example this female doesn’t even burn 3,500 calories per day. Even if with exercise she increased her burn to 3,500 calories, she would have to not eat in order to get close to burning a pound of fat in one day. That would mean she would have to burn over 3,500 calories a day, while not eating, for 10 days. Even then, there are flaws because of metabolic adaptations and energy pathway changes.

Next time you see gimmicks and headlines on web pages or magazine stands, do a little math and have a laugh. If lost in the shuffle – this may help.

Before starting any new diet and exercise program please check with your doctor and clear any exercise and/or diet changes with them before beginning. I am not a doctor or registered dietitian. I do not claim to cure any cause, condition or disease. I do not provide medical aid or nutrition for the purpose of health or disease and claim to be a doctor or dietitian. This is merely an opinion blog. Read full disclaimer here -




  1. Carol

    Going to share this with my ENTIRE facebook. Boy do people need to hear this.

    • Leigh Peele

      If magazine stands suggest anything, people do need to see it. I have seen the claim 3 times this week, which is what inspired the post.

  2. Annette

    Awesome post Leigh (as always), that really puts it in perspective! And now I am back to loosing 10 pounds the old-fashioned way: a tabata-style workout followed by a green smoothie with lots of spinach! πŸ™‚

    • Leigh Peele

      I have to hide my spinach with lots of fruit. Now that I think about it, I am in the mood for one of those.

  3. Sarah @ Weight Loss Tips

    I just came across your blog. I just would like to tell you I’m skeptical of it…. I don’t think in such a shortcuts. I think for a enviable shape we need to create a healthy lifestyle with a well balanced diet and workout. But your idea is good too, the question is how we can keep our weight after that 10 day…

    • bene

      I highly doubt Leigh’s suggesting that someone not eat for a week+ as that would be completely contradictory to everything she’s written on this site.

      • Leigh Peele

        Yeah, you would think the cartoon at the beginning would help convey the message of “gee, this isn’t possible or a good idea.”

        You would think the fact that the whole post is about how it is practically mathematically impossible for the average female and extremely unsafe for a higher weight male or obese person.

        But hey, I guess asking people to read the post before they comment is too much. It was probably spam that forgot their link.

  4. James

    1. Make the pictures a recurring theme.
    2. Excellent, excellent post.

    • Leigh Peele

      Like the picture eh? I was missing my comic but sadly, they were lost in the digital “fire.” So I got out the ole “drawing board” and this popped out.

  5. DADA

    That cartoon is fucking funny.

  6. Andrea Lovegrove

    I LOVED the cartoon. LMAO Great article…I can’t tell you how many times I have told people that their goal to lose 5+lbs a week is just NOT realistic nor healthy. I gotta tell you Leigh that I absolutely love reading your articles educational and entertaining. You are too funny!

  7. Mary

    I think Sara is disguising herself as my dear, loving mother….She only reads the headlines and thinks she knows what the article is about. When you question her, asking about details, she gets mad becasue she thinks I’m doubting her….she still hasn’t figured out that to avoid embarrassment, she needs to read ,not only the header, but more importantly, the body. Hopefully Sara will come back and read comments to her silly post.

  8. Missy

    Bwaahh haaa haaa!!
    Love it!!!

  9. Shannon

    I always wanted to know just how much of adipose tissue was actually lipid, this is a great post, its great to know that someone actually knows what they are talking about!

  10. Boston102

    Hey Leigh,

    I found you via Bret’s links and have really enjoyed reading through your work today. I can think of a lot of strengh coaches who have their shit together, but fat loss is a different story. You are providing quality information here and I wanted to say thanks. Keep up the good work.


    PS – The drawing really is hilarious. I agree to make them a regular feature.

  11. Mike

    Leigh, whuuut? You mean when I drop 10lbs in 24 hours, it’s not all fat?? F! so disappointed… well, at least when I gain the 10lbs back by the next day I know that’s not fat either.. πŸ˜‰ BTW, dropped off a specimen for a 24 hour urine full hormone panel on Monday… the epitome of laziness (or apathy) right there baby, you’da thunk I woulda done this two years ago.

  12. Clement

    Hi Leigh, do you have any recommendations for BMR and maintenance calculations?

    • Leigh Peele

      The standard Harris Benedict Formula works fine. The difference/adjustments I encourage people to make is in determining their activity level correctly. Really take into account your entire day, not just how much you exercise a week.

  13. Wazzup

    Now what if said girl was 450 pounds ?

    do a psmf (say 1000 Cal in protein with some veggies)

    exercise your ass off (4500 Cal’s worth.. go ask Phelps :))

    Walking at 3 mph gives 675 Cal/hour.. so she “just’ had to walk around for 6.66 hours a day (it’s only 20 miles)… repeat for 10 days πŸ™‚

    That’s just the math.. whether it’s feasible …

    Personally I’ve walked 33 miles for 4 days in a row, but not on a PSMF and I wasn’t overweight (and still I messed up my knee!) nor was it my intention to lose weight.. just wanted to walk that much …

  14. Karen Dunick

    Great post Leigh and I love the cartoon.

  15. Zach

    There are two things flawed with this post:

    1) Even if it were hypothetically impossible to lose 10 pounds of FAT in 10 days, that doesn’t mean it is impossible to lose 10 pounds in 10 days. Have you ever seen a wrestler or mma fighter prepare for a weigh-in? They are able to lose 10 lb in just one day from water weight and glycogen storage. Not everybody cares about losing fat, some people just want to lose scale weight for weigh-ins, in which case it is definitely possible to lose 10 lb in 10 days.

    2) You gave an example of a female with an extremely small metabolism. There are some people, such as myself, who have very high metabolisms. I personally eat 6500 calories every day when bulking, so when im trying to lose fat, i can cut down to 3000 calories per day and lose a lb/day. Michael Phelps eats as much as 10000 calories every day. So for people like me and michael phelps, losing 10 lb in 10 days is definitely possible.

    • Leigh Peele

      1) RE: Possible

      I didn’t say it was impossible, I said it was practically impossible, there is a difference. While it can be done, losing 10lbs of pure fat in 10 days would apply to such a small population and even then, would take a higher caloric expenditure than was listed. You are assuming 100% of energy coming from a fat burning pathway. You are assuming a sustainable metabolic rate. No bodybuilder or fighter worth his salt, even on drugs, would attempt a loss of pure fat like in that amount of time because muscle would be extremely sacrificed in the process. They would be left weak, flat, and sick. I am curious how many people you have worked with in regards to real water manipulations.

      In the obese, metabolic rates aren’t nearly as high as people think and adaptations happen just as quick. Possible, yes for a very small population. Likely, not at all. Practically impossible and dangerous for the average male and female, yes.

      2) RE: Your water argument.

      I said pure fat. I didn’t say anything about water. I can lose 10lbs of water in 2 days if I wanted to. This article wasn’t about water, I didn’t say anything about water and the calculations spoke nothing about water. Your argument doesn’t fit to the article. In the future, please read the details of the article.

      3) RE: Caloric burn

      You think Micheal Phelps burns 10,000 calories a day? Let’s do that math.

      Micheal Phelps states that all he does is “eat, sleep, and swim.” He even takes ambien to ensure he gets sleep. He has been quoted as saying he gets an average of 8-10 hours of sleep per night. I will go to the bottom point and give you a 16 hour awake day.

      His official stats are 6’3 and 165 pounds. Now, you have to take into account his level of conditioning and RMR. With the kind of training he does he is likely to utilize LESS energy because of training efficiency. Any small amount of extra muscle, which he doesn’t have a large amount of, would be trumped by his resting heart rate and metabolic adaptation.

      Still, I will give you a standard and not lowered BMR rating.

      BMR = 1875 (rounded upwards) This means at rest, for the 8 hours he is sleeping, he is burning roughly 78 calories per hour. Even if we round upwards to 80, that means in 8 hours he burns roughly 650 calories. This is again being generous and not assuming downgrading due to resting heart rate, lower blood pressure, etc.

      So that means, in order to eat 10,000 calories in a day, he only has 16 hours to burn 9350 calories. That would mean he would have to burn, every hour, 584 calories that he was awake. Based upon his stats, because he is so lean, that would take swimming at a vigorous pace (which he doesn’t do) for 16 hours at a time. No sitting, no watching tv, no nothing. Wake up, swim, sleep. There isn’t even time to eat in there.

      4) RE: Caloric Burn During Bulking

      You would have adjustments after a few days from the decrease of food and energy expenditure would adjust. In a matter of days you would severely decrease in caloric burn and would be losing weight of fat, water, and muscle. While you would achieve impressive fat loss, I highly doubt even in that situation it would be a pure fat loss of 10lbs in 10 days. Even if you did, which I doubt, that still doesn’t apply to the average population or what the article was speaking to.

      Again, this article had nothing to do with water manipulation, supercompensation, or anything else of that nature. This article was discussing the level of effort and mathematical scenarios to trying to lose 10lbs of pure fat for the average population.

      (Edit- It would seem there is a disagreement about his stats. Some places list 6’4 and 195, so here are the numbers for that too.

      BMR – 2070
      87 calories during sleep = 700 calories
      9300 calories left to burn while awake in order to now gain fat/excess muscle on 10,000 calories a day. )

    • Just-in

      Haha Zack are you that stupid? Read the article dude, she didn’t say anything about water. Ten thousand calories a day, LOL The dumber they are, the harder the burn, right? You got schooled, but I want to hit the teacher if you don’t mind. πŸ˜›

      • Leigh Peele

        That was…an interesting response.

        • Lori

          I saw a documentary on Phelps, too, and he did talk about ‘eating up to 10,000 calories’ a day, not burning that, and he didn’t eat that every day. I think Zach was referring to his intake, not burn. I saw him eat piles of food … it was disgusting … and to be honest I don’t know how he can even be accurate on the calorie count based on what I saw. He was eating in a diner and had several plates of food. It was like watching “Man v. Food” but with a more fit host.

          • Leigh Peele

            If he ate like that all the time he wouldn’t be 6’3 and a 165 pounds (or 6’4 and 195lbs, which ever claim is correct). I have had random days where I kill off 5,000, but I don’t say I eat 5,000 calories everyday. The Nathan Hot Dog Champion probably knocks off around that much during training weeks, but the rest of the time he eats a extremely selective and maintenance diet.

            Using occasional example do not justify making blanket statements. If he ate 10,000 calories all the time he would need to burn that or close to it, which is impossible for someone his size unless he didn’t sleep and ran/walk for 24 hours straight. Otherwise he would have more muscle or be fatter with eating that intake.

            • Lori

              I agree on the blanket statement, er, statement. Just had a couple of cents in my pocket and thought I’d give it.

              I’d LOVE to know how you kill off 5,000 calories. That’s like 16 honeybuns. πŸ™‚

              • Leigh Peele

                My extended explanation was just in case someone thought “hehehe see, see, told you he eats 10,000 calories everyday!” Sorry if it came off as attacking, certainly wasn’t meant to.

                And damn right I have killed off 5,000 calories, more even! I have had to put my eating and drinking under the table money with my mouth is. MMM…honeybuns.

  16. JenD

    I always thought the claim from Phelps was pretty outrageous, but now that I see the math, its ridiculous.

  17. John

    It’s great to see other’s who believe as I do. Koodos to you Leigh!!!

  18. Lisa

    How does the show Biggest Loser do it? Some of those peole lose 20-30 pounds in the first week.

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