Welcome to The Fast Diet › The official Fast forums › Body › General health › TDEE and how it’s calculated on our site
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24 Jun 14
We’ve had a couple questions about our TDEE calculator, how we get the numbers and why different TDEE calculators give you different numbers.
First, TDEE is “total daily energy expenditure” and is simply an approximation of the average amount of calories you use over a day. Second, here is a link to our TDEE calculator. 🙂
There are a couple of different factors in the TDEE – the BMR (basal metabolic rate – your basic metabolism, ie the energy required to keep you alive) and the “activity factor”. The BMR can be calculated a number of different ways. We use the Mifflin-St Jeor equation as it has been shown to be the most accurate.
TDEE is the BMR scaled by the activity. It generally goes between 1.2 (sedentary) and 1.9 (hard sustained exercise every day or more often) and scales linearly. The differences I’ve seen in various calculations with this usually have to do with the exact wording of each point – this can lead people to choose a higher or lower number and, sometimes, more activity factors in between the ones we have, eg 8 choices instead of the 5 we have.
The things to check on different websites are:
1 – which BMR equation they’re using
2 – that you’re comparing like with like (i.e. choosing the same activity level for both). Our activity level descriptions tend to lead people to the lower number – this is deliberate as most people here are trying to lose weight (and tend to overestimate the amount of exercise they do… or at least I do.)
The best way to think of TDEE is an estimate. Neither TDEE nor calorie counts can be exact, but both are extremely useful in losing weight, maintaining weight and gaining weight (depending on what you want to do!).
25 Jun 14
Thank you for posting this. I think it will be invaluable for anyone starting out on 5:2.
I had never even heard of TDEE prior to finding this site (about this time last year) and it was a revelation to me. I had already figured out for myself that using ‘Ms. Average’s’ calorie numbers (2000) for non-fast days, was not going to get me down to my ‘goal weight’ and the TDEE & BMR numbers have really helped me keep on course, as my weight loss slows as I get closer to my goal.
I second everything Tracy said. It’s not that it was a totally new idea for me, but it gives me a good estimate of what I can realistically eat over time.
I am still confused. I have a lot of weight to lose (9st) and on non fasting days I don’t know how many calories I should eat. My BMR is 1851 and my TDEE is 2545. On the calculator it says I should eat the TDEE on non-fast days but I seriously don’t think I could eat that amount any more. Also I have read that it is okay to skip meals as well so I skip breakfast on the days I go swimming. Any advice?
The TDEE is a suggestion. Don’t go over the number of calories in your TDEE. Eat what you need on your non fast days.
Chillitotes, I agree with Amy C. that it is not necessary to eat when your body is saying, “I’m full!” It’s when people consistently eat over their TDEE on non-fasting days that they may not lose weight. One thing to do is to calculate your TDEE at your goal weight. You don’t need to start eating at that level right now, especially if you have a lot of weight to lose, but it can be helpful to get an idea of how much you should be eating to maintain when you get to goal, keeping in mind that everyone is different, and the number the calculator gives you is an estimate and may need a bit of tweaking to fit you exactly.
26 Jun 14
Hi Chillitotes, yep – don’t overeat if you don’t feel like eating your total TDEE allowance. That’s all it is, an allowance for someone of your weight, height, age, sex and exercise level. TDEE is the maximum you should eat on a non-fastday, if your aim is to lose weight, BMR is the minimum, so anywhere vaguely between the 2 numbers is your aim for now.
Don’t forget that the figures will change as you lose weight and if you put your ‘goal weight’ into the TDEE calculator (instead of your real current weight) it will give you your TDEE for when you get to maintenance level. So I would say that if you do that and the ‘future TDEE’ is more than your ‘current BMR’, you could just aim for that ‘future’ figure on non-fastdays and start getting your body ready for what it can expect to get for the rest of your life.
28 Jun 14
Well, this is interesting. This TDEE business caught my eye on the homepage as soon as I registered.
In the Fast Diet book, Dr. Mosley says it’s not necessary to count calories every single day. I heard Dr. Mosley is revising his book for 2015. So, do we count calories EVERY SINGLE DAY now?
If so, I’m out. I just can’t do it every day. Two days is enough for me. Yes, I hate counting calories.
Any feedback is appreciated.
30 Jun 14
No, of course you don’t ‘have to’ if you don’t want to but a lot of people do (they’re coming from other ‘diets’ where they just can’t help themselves or they’ve plateaued and realised that they need to pay attention on non-fastdays or they will tend to over eat and undo all their good work from fastdays).
I don’t COUNT as such but I know very well what calories are in most things I eat, so I just keep a vague track of what I put in my mouth on non-fastdays and try to remain under my TDEE. It’s not at all a problem and I never weigh & measure, as I know by sight how many chips add up to 200kcal(ish) or how much rice = 200kcal(ish). I also know by sight how much Alpen or whatever I can have for my fastday meal, so I never even actually COUNT calories on a fastday either.
I understand where you are coming from, hating to count calories, but unfortunately to some extent you have to.
I am not sure where you read it in the book but there is a huge difference between 5:2 and ADF (alternate day fasting) which is based on Dr. Krista Varadi’s research, which Michael uses as the research base for his book. There has been no other clinical research done on the real effects of 5:2 and Dr. Varady has forbidden Michael to use her research for his book in future reprints.
With ADF you do NOT need to count calories as if you go over your TDEE it is not the world. With 5:2 you have to stay under your TDEE. Now how would you know that you are not going over? My TDEE is not exactly high, so for me to go over is very easy! Not only do I count calories on my non fast days, I even weigh my food.
5:2 is nothing but another form of diet where you try to create a weekly calorie deficit by under-eating on two days. It all boils down to calories in versus out. If you over-eat on non fast days it will not work.
Hi, I am coming back to 5:2 fasting. I’ve been away for a while, but am back, as other members of my family are now doing fasting, and some are even on this board!
It is actually incorrect to say Dr. Mosley’s book is based solely on Dr. Krista Varady’s research, and that there is no clinical evidence for 5:2. That is so wrong. Dr. Harvie has respected, researched studies out there showing the positive effects of 5:2, and in fact, Dr. Mark Mattson, a very well known fasting researcher is conducting a study this year on 5:2 done on humans (not mice). I can’t wait for the results of that study.
I have Dr. Harvie’s two books, The 2 Day Diet, and also The 2 Day Diet Quick and Easy. While I don’t follow her recommendations of eating a Mediterranean Diet the remaining five days, I am starting to fast on two consecutive days a week, eating mindfully the remaining 5 without counting.
Yes, I read about Dr. Varady’s rant against Dr. Mosley. I won’t even dignify it by posting the link here. I notice that Dr. Mosley has taken the higher road, not ever commenting on it, and I also notice that Dr. Varady’s new book did nowhere near the sales of the Fast Diet. In fact it never even made any bestseller list.
I will always be grateful for Dr. Mosley and Mimi Spencer for getting the word out about this lifestyle…which I am returning to and will remain on. I have all their books as well, which will be so helpful to me upon my return to this lifestyle.
Coffebrain, Dr. Varady was in my opinion rightly upset about Michael using her clinical research findings for his book. Her book came out later and yes she is not a journalist that uses the media widely to promote her book, but rather a researcher who does her own research.
I am aware that there are studies done NOW re the benefits of 5:2, but I am not aware of a longer term CLINICAL research re the benefits of 5:2 – general fasting yes, but not the 5:2.
This is not to say that I have any problems with 5:2, I am grateful that it provides an alternative to traditional fasting methods.
I would love to see more though about the benefits of a healthy diet and the necessity of exercise to maintain critical muscle mass in his updated version. While a calorie might be a calorie in terms of losing weight, 100 calories of chocolate result in a different reaction in your body than 100 calories of veggies. Also, if you lose weight you very likely also lose muscle mass, which in turn slows down your metabolism. A bit more on how to retain your muscles would be very helpful. The fastexercise book again refers to weightloss but omits this crucial point.
P.S. Nowhere did I say he “solely” based his book on her research, but it is mainly based on her research.
1 Jul 14
1. Of course Varady uses the media to promote her book. That whole “Mosley copied my research” saga was to draw attention to her book. It just didn’t work! Her book didn’t sell that well. Dr. Mosley openly states in his book, he is his own experiment. HE COPIED NOTHING. He just discussed the various methods of fasting out there. Varady opened a website for her book and also a facebook page. She has been on television shows here in the States promoting it on many morning news shows. I actually find her methods of self promotion disgusting, attacking Dr. Mosley like that, but Dr. Mosley is taking the higher road than I by not even discussing the matter. I have so much respect for him.
2. Of course clinical research has been done on 5:2. Google Harvie and you’ll get them. And I do mean clinical…uh, on humans not on rats. Dr. Mark Mattson, esteemed fasting researcher is conducting a study this year based on 5:2, NOT on alternate fasting, which he stated in a you tube video, is probably too hard for the general public to follow (amen to that too). You can google that as well.
2. The Fast Diet is not based mainly on her research. Many forms of intermittent fasting were talked about in Mosley’s book. In fact, you can say his book was mainly based on Harvie’s research, since her diet is a 5:2 one as well.
Well, I’m not here to argue and won’t be pursuing this topic any longer. But I do find it odd that you’re on Dr. Mosley’s website and not too supportive of his wonderful book that represents this website.
Have a nice day.
7 Sep 14
I am keen to lose about 5 kilograms and really hope this diet works for me
Hi Harvey and welcome:
Hope this helps: http://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/
16 Sep 14
Just started my Day 1 of fasting this morning…I guess really it started just before I went to bed – giving me a head start whilst I was asleep! lol I’m currently a size 22 & would like to eventually get back down to a size 16. I’m 55 & have put on a lot of weight in the last 5 years mainly because of PTSD. I’ve seen all the docos Dr Mosley has made, & they’re inspiring! I’m not one for exercise, as my work is already physical. However, in saying that, my work has suffered from the PTSD too – so it’s a catch 22 – having PTSD is tiring, so, there’s not enough work for me to physically be active (make sense?). I’m very pleased there is a tracking system set up & there’s a page to ask for help or voice one’s wins! Thank you & good luck everyone with your goals!!!
18 Sep 14
Hi all, Im on my first fasting day today too. Im 39, female and need to lose 15kg. I am in Melbourne Australia and seen Dr Mosley on our news/current affairs show and bought his book the next day! I am a nurse so am on my feet all shift and have also cut out sugar (at least 6 months ago) bread (1 month ago) and seen no results whatsoever! One of the other nurses at work knows several people on this eating plan who have had great success, Im praying she can add me to that list too soon 🙂 My biggest worry is feeling hungry all the time. Im noticing everyone praising the eating plan but can everyone who reads this please post how long you have been on this plan and how much weight you have lost so far? Thx 🙂
21 Sep 14
My tdee is 1800, no way can I eat that much, but someone told me to eat between your bmr & your tdee On a fast day eat 1/4 of your tdee.
I’ve been using one form of IF or another since 2011 (ADF and then 4:3). I’ve shed 60lbs and been in maintenance for some time.
NB: I had a Dexa scan (tedious back story) and learned that I have very low muscle mass and despite my age and activity levels I’m clinically sarcopenic. My BMR is <900 a day; my TDEE on a sedentary day is approx. 1000 kcals and on a more active day, it’s <1300 kcals. Despite this, I still managed to shed the weight I needed to lose.
I should have mentioned that my TDEE and BMR calculations were calculated as part of the Dexa scan and based on my actual amount of muscle mass, not the average amount assumed in a general TDEE calculator like this one. (The calculation still used the Miffin St Jeor formula, like this one does.)
I have had dexa scans for my bone density but I have never heard of a dexa scan giving those results/calculations. How does a bone density scan tell me my BMR?
If you search for
dexa scan “body composition” or
dexa scan sarcopenia
it should tell you how Dexa scans can also be used to give an accurate estimation of body composition as well as bone density.
NHS Choices mentions this application: “Total body DEXA scans can also be used to measure body composition (the amount of bone, fat and muscle in the body). This type of scan is routinely used in children, but is still a research application in adults”.
Most privately purchased body composition reports will also include an estimation of your BMR and TDEEs based on this measurement and analysis of your body composition. Scans for sarcopenia can also give you this information as a guide for you as most people with sarcopenia are also categorised as having sarcopenic obesity.
7 Feb 15
Nik39 – 2 years on the plan. 8kg lost in 3 months, 16kg in 6 months – stayed around that weight ever since giving me a BMI of 22.5 or less for the vast majority of the last 18 months. Intend 5:2’ing for the rest of my life because I enjoy the feeling of control it gives me. Also I’m much healthier than I was 2 years ago.
8 Feb 15
I’ve found this very interesting. I’m usually on another site. I too have been confused with TDEE. it is encouraging to see that some of us take longer to lose weight than others. I’ve only been doing the 5:2 for just under a month and have lost 1 1/2 kilos. I know if I stick to this way of life my weight will gradually come down. I agree that this 5:2 must become our way of eating in the future. It is not a fad diet. It’s been tried and tested by Michael’s peers in both in the UK and the USA. I’ve tried numerous fad diets in the past. Mostly Atkins. I did lose weight but it was just not sustainable. The 5:2 is not difficult.
Take care all and good luck.
14 May 15
I am still confused around how many calories I should eat on a fast day. My TDEE is 1,400 calories so if I should eat a quarter of my TDEE on fast days then I should only be eating 350 calories instead of the stipulated 500 calories which I presume is for a person with a TDEE of 2,000 cals. Does this make sense and can anyone enlighten me?
15 May 15
You are correct.
500/600-2000/2400 is the standard and you can use this, but for some, usually short ladies, 1/4 TDEE is better. Principal is eat overal about 80% of what you need in a week. ie 2000cals a day is 14000 a week. 5 x 2000 + 2 x 500 = 11000 cals is 80% 3000 cals saved = about 1lb
If your TDEE is 1400 thats 9800 a week, doing 500/2000 you wouldnt lose weight. But if you did 5 x 1400 + 2 x 350 = 7700 = 80%
Though 5 x 1400 + 2 x 500 = 8000
If the 150 calories is the difference beween enjoying the fast days and hating them, use the 500.
Of course this is just the maths, nothing works out exactly like the maths.
Some people, even some if us shorties, use the TDEE of the target weight, reducing calories further. Makes you very careful about the calorie values of food.
Thanks so much Milena. Now I can get going and lose some weight.
good luck, let us all know how you are getting on m x
28 May 15
Fastshirl and milena, I also follow that logic and have less than 350 cal on a fast days (sometimes I have nothing if I can distract myself long enough)
However, if you do a quick Google search you will find that the 3000 cals saved = about 1lb loss is not actually backed up by evidence and no one knows where it came from http://www.zoeharcombe.com/2014/06/the-calorie-theory-prove-it-or-lose-it/
Hi Mrs Civ
I’ve always known the calculation of 9g a gram = 4000 plus of fat but stay with the 3500 just to save the arguements, especially as it is the most quoted – the point was that the 5:2 2000/500 calories can be just treading water for short, sedentaryy womenfolk like me – the pound a week average is also just a guide, you can see from this forum no one loses a pound a week.
To quote Captain Barabossa of POTC of of context ” more what you’d call “guidelines” than actual rules”
I wish the TDEE calculator here used BF%. BMR can be very deceiving. Two people of the same height and weight can have a very different TDEE because of the amount of muscle they have. The strategy to eating closer to your goal weight and TDEE is a very good one because as you lose fat your real TDEE actually doesn’t change much because fat is not very metabolically active. I.E muscle burns calories 24/7, fat burns almost none.
It is actually possible for your TDEE to go up as you lose fat if you are lifting weights and gaining muscle as you burn fat.
Muscle burns calories at about 6 per pound, fat at about 2 per pound. There really isn’t that much difference: http://www.livestrong.com/article/256919-how-many-calories-does-muscle-burn-compared-to-fat/
That means if you replace 5 pounds of fat with muscle, you will burn about 20 calories per day more – not a lot. That is why TDEE calculators do not take into account muscle mass.
Oh but there are TDEE calculators that account for BF% available. http://www.fat2fittools.com/tools/bmr/
I agree that the latest research indicates that muscle burns 6-10 cals at rest. But with exercise it burns a lot more. If you are doing effective weight training that requires the body to do repairs of the muscle it’s even greater.
So BMR doesn’t change a lot with more muscle but TDEE can change quite a bit
29 May 15
I used that calculator. It said my current bmr is 1413. I put my goal weight at 10 lbs less than what I am now. It then said that my current calories to eat to get to my goal would be 1644. That doesn’t make sense. Why would I eat more than my bmr to lose weight??
BMR has nothing to do with weight loss (or, from a practical standpoint for the average person, much of anything else, really). The TDEE controls. So if your ‘recommended’ number of calories are less than your TDEE, then you will lose weight. But if your recommended caloric intake is higher than your TDEE, there is a problem somewhere!
Simcoeluv welcome back! I missed you
Thanks Applepie. Just back from travels and thought I’d stop in to see if the Forum was still here.
Seems to be as lively as ever!
28 Sep 15
Hi Nik, Good luck with your weight loss. I’m also a Nurse (48 year old male)but no longer on the wards as I work in a sedentary desk based role. I’m trying to shed 28 lbs of fat. The one thing that appealed to me about 5:2 is the fat loss. Can’t say I’ve lost any weight yet – I only started last week but I feel thinner and healthier if that makes any sense. I’ve not felt hungry. I tried using Slimfast for my first day – not the best idea I’ve ever had but tried it for ease of use. I now intend to use proper food and count the calories! I’m using ‘My Fitness Pal’ to track my calorie intake on my phone. I hate exercise with a passion but have just downloaded the 7 minute a day plan also on my phone to do some HIT (high intensity training) as how bad can it be?
Good luck with your weight loss. I hope to hear about your future successes on here!
29 Sep 15
Hi Nik I am a 63 y/o nurse wanting to lose 10kg lost 5 kg in 8 weeks feel better clothes fit better still have 5 kg to lose but it’s slower now i am in my 14th week not worried
Hope to lose more as summer hits Melbourne then can go walking.
It does work I have the Lazzuppa soups from Coles or woollies the satchet ones are only 23 calories good for lunch /when hunger pangs hit.
10 Apr 16
Hi, my TDEE is approximately 1700 calories but I tend to go over it quite a lot on non fast days. What happens if I do this? Is it very bad? Will this affect my fast days calories?
When you over eat you will not lose much weight, if any.
Here are some tips: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/
I too am struggling at present with overeating on my non fast days. I did so well when I first began the 5:2 diet just over 12 months ago. I achieved my goal weight within 6 months by calculating my TDEE at my goal weight and only eating 1/4 of this on fast days and not going over the TDEE on non fast days. I even did this on alternate days initially. My TDEE is 1400 and therefore a maximum of 350 cals on diet days. Since achieving my goal weight we have had Christmas and a holiday away where I stuck to 2 fast days per week but the calories rose on non diet days. This has resulted in me putting 6lbs on and since getting back to the 5:2 regime I have been lazily eating 500 cals on fast days and not counting calories for the rest of the week. Therefore I am just maintaining my weight at the extra 6lb excess. This message from you has spurred me on to get back to no more than 1/4 of my TDEE on fast days and no more than my TDEE for the other 5 days. As a previous responder stated, you soon get used to the calorie counts of certain foods and set meals and therefore don’t need to always count calories. Also, I think it is a good idea to calculate the TDEE for your goal weight and stick to those figures and aim to achieve this for life. Thanks for spurring me on to help me get rid of this stubborn 6lbs. I felt so good at my goal weight. Good luck
25 Sep 16
I will start this week. I have been trying to lose 5kilos, I could acomplished this in the past very easy but is getting hard now. Looking forward to see how this work
27 Aug 17
Hello, what happens if I eat less than the 500 cals recommended on fast day? Is it bad?
You potentially lose weight faster….on the assumption that you don’t overcompensate on your NFDs. Is it bad? No.
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