Intermittent Fasting -The BBC Horizon Documentary

Andy MorganLeangains & Intermittent Fasting Guides61 Comments

BBC Journalist Michael Mosley – Gave a 5:2 version of Intermittent Fasting a try.

It was great to see the BBC picking up on Intermittent Fasting this week in an hour long episode of Horizon. As a popular show, it will have been watched by millions of people.

When I posted this on Facebook Lyle McDonald shot back with this:

“Predicting the future: folks in the UK will now adopt IF’ing. They will starve all day and binge eat at night and wonder why they are still fat.”

Unfortunately, I think he’s right. People will miss the wood for the trees. There is a very clear nutritional hierarchy of importance for losing fat:

1. Calorie Intake vs Expenditure > 2. Macronutrient Split > … 3. Timing

Simply skipping breakfast is not going to get you magically lean and shredded. Never lose sight of this and don’t let your friends fall into the trap. I’d like to talk about this and a couple of other points raised in the documentary.

Nutritional Hierarchy of Importance for Fat-Loss/ Muscle Gain

In broad simple terms:

  1. Calorie intake vs expenditure controls whether you gain or lose weight.
  2. The macronutrient composition of your diet (carbs/fats/protein) controls the ratio of how much fat vs muscle is lost/gained.
  3. Nutrient timing, for the non-athlete, is a very distant third. -All the research so far backs this up.

This means that you are much better off putting your efforts into getting the right quantity of food and macronutrients for the day before stressing over the timing of things; it means you don’t have to always sprint home from the gym to get a post workout meal in your “anabolic window”; and most importantly it means that you can’t just stuff your face with reckless abandon, thinking that the fat burning during the morning fast will take care of it.

Yes, fasting – which is a part of nutrient timing don’t forget – can help with stubborn fat loss, but only when the other two things are firmly in place.

5:2 Intermittent Fasting vs Alternate Day Fasting ADF

The journalist did a “5:2” version of IF, where he ate just one small lunch (~500kCal) on two days of the week and then just ate whatever he wanted for the rest. Blood lipids improved and he lost a lot of fat. -Fairly painless, very simple, and gives the benefits of fasting.

Michael also tried Alternate Day Fasting (ADF). The scientist that has been studying people doing ADF said she found that as long as people hit their macro targets for the “fast day” despite the instruction to “eat whatever they wanted” on the other days people wouldn’t over-eat enough to undo the previous day’s good work. -There was still an overall calorie deficit.

In looking at ADF vs 5:2 it’s quite easy to see why, that’s 7 vs 4 fast days in a two week period which is a significantly greater deficit. Would this make ADF better for the average person then? Probably not. Michael said he found it too restrictive whereas the 5:2 was manageable. The key to success with the 5:2 though is to eat “normally” on your regular days rather than binge.

The above two methods work through calorie restriction. -Number 1 in our hierarchy. While this isn’t going to give a gym trainee the very best results (try the Leangains principles), they are free, very simple and perhaps a good introductory step or way to help out an overweight friend that wants to diet.

The part about IGF-1 (Insulin-like growth factor 1)

The documentary goes pretty heavily into extolling the benefits of IF as a life extension tool / way to prevent diseases by keeping IGF-1 low. Let’s not pretend here, the first thing you thought when you heard this wasn’t about living a happy and cancer-free life till you’re 90 was it? You thought, “Oh shit, does that mean it will affect my muscle gains?” Fortunately the answer I believe is no.

To quote Alan Aragon here,

“While it is true that IGF-1 can have powerful effects within the muscle, we also have to keep in mind that it’s the muscle-specific variant of IGF-1 – now commonly known as Mechano Growth Factor (MGF) – that is relevant to muscle anabolism. The circulating form has very little effect on skeletal muscle.”

Or as Reddit user Arrozconplantano put it quite succinctly,

“There is no evidence systemic IGF-1 causes hypertrophy.  It’s not worth thinking about.”

If this really concerns you then feel free to go and pester Martin or Alan about it. They are far smarter then me and will be able to give you better answers.

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I’ll have a guest post in the coming weeks by Beyond Brawn author Stuart McRobert.

Thanks for reading. -Andy.

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Andy Morgan

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61 Comments on “Intermittent Fasting -The BBC Horizon Documentary”

  1. Pingback: Se não está quebrado...Dieta & Malhação

    1. Did the link break? Oh well, wasn’t required watching anyway. Sure there is a torrent out there somewhere if you’re desperate to watch it.

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  3. Where can i Find info about how to calculate My macros…..Please been looking all over and not finding à proper help

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  5. If one is skinny fat at around 15 percent bodyfat, rather weak and starting training, wouldn’t he be better of not to do any IF/macro counting and just eat normally with adequate protein and grow, then start to incorporate Leangains diet?

  6. For what it’s worth, I don’t do IF because it’s some kind of voodoo magic for fat loss. I do it because:
    1) increased energy level and mental clarity during the fasted state. The further into the fasted state I go, the more energy I have.

    2) I get to eat like a man, not a boy. I don’t like eating 5 or 6 little kiddie meals. I like to eat a couple big meals a day. When you pack all your macros into just 2 (or 3) meals, you get more variety in what you can eat and still fit your macros.

    And as others have stated, you can still go over your cals when IF’ing. If I’m going out to eat with friends, I’ll fast all day and just eat the one meal. But, with appetizers, entree, and dessert; I can easily blow past my daily cals in that one meal. 🙂

  7. Pingback: Jonathan Evatt Online | The Virtues of Fasting

  8. Good analysis as always. Funny, I popped on the site to look for the answers to a question I’ve had about this very topic. Specifically, meal timing with regards to the fasting and training schedules.

    I’ve been lucky enough work-wise to keep a 12pm-8pm eating window (2 meals), rising at 5am, training 11am-12pm. I’ve been getting shredded; the system works! Well, work has changed and now I often need to workout early morning. When I follow Martin’s advice and keep up the fast post-w/o and BCAA every 2hrs until my feed at 12pm, I feel TERRIBLY wiped out and starved all day, vs quite happily satiated when I feed big RIGHT AFTER my training session at 12pm.

    How important is keeping the 16hr fast and scheduled eating windows? Is it heresy to train early morning, eat big, fast all day, eat big at 8pm, and go back to IFing and a 12pm-8pm feeding/fast schedule on rest days?

  9. HI Andy, I am a vegetarian and I eat Rehydrated Soya Protein on off days, would you recommend it?

    1. Recommend? No, I recommend huge steaks, roast beef, chicken breasts and bacon. I’m not a fan of resorting to supplements to get your protein so I don’t keep up with the different brands. Obviously as a vegetarian you have little choice when trying to get the recommended levels of protein here. Just be aware of BCAA content as not all protein is made equal for muscle protein synthesis.

  10. Hi Andy,
    if I want to combine 1x a week training with Leangains diet, should I still include 3 training days in terms of macros or it’s better to use Your guide and make it 6 rest+1 training day? I understand that the point of “training days” is to allow growth, but I suppose the diet is “prepared” for 3 training days which is reflected in all equations used. The third option would be a compromise: 2x a week training and 2 training days.

  11. hello!i’m 26 year old male and train over an hour cardio or strength train 6 days a week. I’m really keen to try a 5:2 IF but i’m just concerned about my fasting day. can i still train and fast? sorry if i’m repeating a post!!

      1. yes it’s appearance goals, wish i was an athlete!!!sorry i miss explained, i train either cardio for over and hour (cycling to work),or strength train for over an hour per day so 6 training sessions a week. i was going to strength train on my fasting days as i don’t fancy cyling 13 miles to work,12 hour shift then cycling 13 miles home without food…unless you think it would be ok?any thoughts please?thank you for your reply, you’ll be sick of replying to all million of us soon so i thought i’d sneak in for another post!!! 😀

        1. Cycling in the morning fasted isn’t an issue. Eat lunch and you don’t need BCAAs for the journey home either. Don’t train 6 days a week with weights though.

  12. Great piece Andy, just what I’ve been thinking about. I thought the show was motivating, if a little simplified. And yes, I did worry about the whole IGF-1 Vs physique thing. I’ve reached my target weight and BFR with Tim Ferris’s Slow Carb approach and find it easy to maintain with it. But I’m also interested in the benefits of IGF-1 lowering for health reasons.

    So I’m thinking of mixing it up a bit: slow carb mon, wed, fri, fast tues, thurs and adding fruit and whole grains to the weekend (and a few beers). With some resistance training on the slow carb days.

    I feel more confident now that the fast days won’t impact so much on the slow carb work out days now! Any thoughts?

    Cheers again for covering this!

    1. Thoughts:
      The whole “slow-carb” thing works through calorie restriction via restriction of food choice, not the GI or II index. Thus if you’re at maintenance right now with 7 days of your slow-carb diet then adding two non-rescticted days without making adjustments to the others will lead to a weekly surplus and this gain.

  13. Hi Andy. Usually i would work out on the Sunday but i can’t because of a family event out of town. There will be a Hugh meal of the best foods though. Do you think working hard on Saturday instead will still improve partitioning for Sundays meal if i kept calories and carbs lower on the Saturday?

    I don’t want to limit food choices much as now, thanks to IF, i have a reputation to maintain regarding how much i eat.

    1. Hi Andy,I am trying to find my own way. Do you think Eat Stop Eat 2x week 24h fast and 1x week High Intensity Training with dumbbells for 30 minutes can lead to similar results as presented here?

        1. I meant if You think it’s possible to get the same physique as from Leangains/ Starting Strength or other here mentioned programme…using HIT once a week and IF(ESE) 2x24hours a week + sleep 9 hours. Theoretically, caloric restriction is caloric restriction and training is training. I am pretty sure it’ll take more time than 12 weeks but I believe I could get there. I am 22yo, former 179cm/80kg skinny fat, now rather skinny at 179/71 but muscle building is slow. My goal is cca 8 percent bodyfat and appearing really lean and musculular.

  14. Andy, congratulations on the 1 million hits! And i am really looking forward to reading Stuart McRobert’s post!!


  15. As nice as it was to see IF being discussed in the mainstream on the BBC I thought the program was average at best.
    Did you happen to catch the previous episode about HIIT? I thought that was far better.


    1. In honesty Scott I think both programs were a disappointment. Points and science cherry-picked from research to make it more sensational and interesting for the main-stream masses, trying to make something complicated black and white. However sometimes oversimplification is a necessary evil to help motivate people to get off their arse and do something. -If it were too complicated then people would simply switch off.

      I am however grateful that the BBC decided to do something on exercise, IF specifically. -It adds credibility to the idea of it.

  16. What about the point that protein ingestion effect IGF-1 levels? Which would suggest that a high protein diet would lead to high IGF-1 levels. But intermittent fasting can stabilize IGF-1 levels? It was the only point that worried me a bit.

  17. I would look forward to that post. The reduced protein intake recommended in the doc and the fact that he did no strength training puts leangains at odds with what he attempted.

    1. Which merely raises the question, how much does lowering protein intake affect IGF-1 vs the fasting part? Does the one offset the other by a greater amount? How important are each for long term health on balance?

      1. I was asking a few other experts of their opinion on it and the consensus was that whilst the programme associated higher cancer risk with higher IGF1 due to a high protein diet; in reality high carb diets produce more IGF-1 singalling via insulin activation. If I can find the studies I’ll post them. I would have thought if that was true – then we’re sort of back to square 1??

  18. Good article, my only thought is though…. if you have a body, you are an athlete. Period.
    Therefore, you must strive to have nutrient timing on the workout days you find most draining if you ARE a “non- athlete” out of the little days that you DO workout. Other than that I call it sheer laziness and phuckarounditis for not doing things as such to improve smoothness of results.

    1. By “athlete” I was referring to an individual that trains multiple times a day. – For these people nutrient timing is definitely important.

  19. Awesome article as always Andy. This article will definitely set things straight fpew some who might have the notion that IF is simply a pass for binge eating, or so I have heard on many social, networks in recent weeks.

  20. Nice write up Andy.

    What I liked about the documentary was that they looked at different \’styles\’ of fasting.
    I think they underestimate peoples ability to overeat during the \’eating phase\’ though. Like you said, not eating breakfast but still being in a calorie surplus isn\’t going to get you anywhere.


    1. Yes, I think you’re absolutely right. I meant to emphasise that. There are definitely some people that put down huge quantities of food when told they have free reign. -ADF or no. They’ll screw it.

  21. So glad someone in the know wrote about this. I feel it being on during the Olympics will have made the effect of it very minimal.

    Sent from my iPhone 4S

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