Pocket Guide to Intermittent Fasting

Intermittent Fasting (IF) is all the rage these days, and there are a variety of different protocols out there, pioneered by people ranging from Ori Hofmekler (The Warrior Diet), Kate Harrison (The 5:2 Diet), Michael Mosley (The Fast Diet), Bert Herring (Fast-5), John Daugirdas (The QOD Diet), and Martin Berkhan (LeanGains), all the way to Jack Kruse (Epi-paleo Rx).  Chances are you’re probably unwittingly already doing one of them, at least intermittently.  The theoretical benefits are seemingly endless (albeit via few human trials), beyond the scope of my brain.


Non-IF: grazing; 6-8 meals per day.  Only significantly fasting duration occurs while asleep.
Normal-ish?: 3 squares.  Two 5-hour fasts, then fasting while asleep.
Eat Stop Eat or The 5/2 Bikini Diet: Eat only a small dinner 2 days/wk (600 kcal), eat normally other 5 days.
ADF: Alternate Day Fasting – 75% restriction on day 1; 25% surplus on day 2.
Leangains: Skip breakfast.
The Warrior Diet: Skip breakfast & lunch. (+1)
EOD: eat only Every Other Day.  36 hour fasts – from dinner on day 1 until breakfast on day 3.

Some of them have data (much of this was taken from my article over at BuiltLean), most of which only looks at feeding frequency, not diet per se (except Klempel).


Divide and conquer

ADF (75% restriction on day 1, 25% surplus on day 2) (Klempel et al., 2013)

They tested this with low fat and high fat versions (all food was provided and both diets worked, with a modest advantage of HF over LF):

ADF data

Fat mass declined slightly more on HF, and muscle actually increased in both groups, slightly more on HF.  The changes in muscle mass are surprising, as there was no exercise intervention and protein was held at 15% in both groups (but varied between 19 & 94 grams/d).

Leangains – (Lefitsky and Paconowski, 2013) :/

The Warrior Diet (Stote et al., 2007)

Technically, this diet was designed “to reduce meal frequency without caloric restriction.”  Disadvantage: the participants were hungry (this wasn’t assessed in Klempel’s ADF study).  And even though they tried to maintain weight, they couldn’t.  Warrior dieters lost 1.7% of their body weight.  However, similar to ADF, body fat declined [markedly, by 11.8%] while muscle actually increased [modestly, by 1.6%].

EOD (Heilbronn et al., 2005)

LOL body weight if you only eat every other day:

EOD data

By the end of the study, they lost 2.5% body weight and 4% body fat.  Thus, fat comprised 57% of the weight lost (body fat declined slightly from 23.7 to 23.0%).  It seems difficult to completely make-up for an entire days calories on the subsequent “feasting” days – the participants were encouraged to eat as much of whatever they wanted until they were satisfied and still couldn’t maintain weight.  And resting metabolic rate declined by about 100 kcal/d which, as Anna pointed out here, might bode well for longevity.

Under weight stable conditions, EOD doesn’t seem to affect body composition but still hampers energy expenditure (-59 kcal/d in this study Soeters et al., 2009).

ADF vs. The Warrior Diet vs. EOD

ADF: inferior to The Warrior Diet and seems like it would require tedious “calorie counting” (I’d feel like a sucker doing it).

The Warrior Diet (one big meal per day): unwitting weight loss, and improved overall body composition.  +1.

EOD: weight loss, but lose a lot of muscle too.  Not good in terms of body composition, but the reduced metabolic rate may be beneficial in the long run (?).


BTW wrt The Warrior Diet… 2500 kcal is a lot of food to consume in a 4 hour window:

9 large potatoes (3.3 kg, 7.3 lbs), or

3 sticks of butter (25 tbsp, 356 grams, 12.5 oz), or

2 bars of Scharffen Berger’s 99% Cacao (491 grams, 17.5 oz.)



calories proper


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  • Kindke

    My conclusion was also that the warrior diet is the “optimal” way to eat, with respect to timing.

    I definitely notice I carry more muscle while doing 23/1 IF

    Hunger is not a problem provided you eat plenty of protein and fat, the circadian rhythm of ghrelin will eventually adjust to match your 23/1 eating schedule.

    The disadvantage is like you said, consuming all your food in a small window. Afterwards your always pretty much “done” for the day and just lay around being lazy.

    • http://www.caloriesproper.com/ William Lagakos

      Hi Kindke,
      Thanks for the comment – your experience with Warrior Dieting seems to be in line with these data. If I exercised in the evening I might be tempted to try it, but I don’t like the idea of trying to do the gym & take down a huge breakfast before a long day of work. Works fine on non-exercise days though.


      • Kindke

        The large single meal is better eaten in the afternoon or evening, cortisol is very high in the morning so its counter-productive to be eating then.

        Assuming you wake at 8am and go to bed 11pm, Ive found the best time for the meal is around 3-4pm.

        Always workout before meals. Catabolism buffers anabolic rebounding,

        • Kindke

          /BTW 23/1 wasnt so great for fat loss in my experience I lost 10lbs before stalling. I could only lose further by cutting carbs to atkins induction levels.

        • http://www.caloriesproper.com/ William Lagakos

          Exercise after fasting for 23 hours!
          My case for pre-workout nutrient timing: http://caloriesproper.com/?p=2055

          • Kindke

            yeh ive seen alot of people advocate pre-workout nutrition but it doesn’t work for me, my performance is substantially better if im fasted. Eating usually makes me more sloppy and lazy.

            I think the best way to approach 23/1 is workout in the morning then have the big meal for lunch, or workout in the afternoon and have the big meal for dinner.

            either way exercising after 23 hrs of fasting should be fine, catabolic activity should always set you up for an anabolic rebound, why do you calorie restriction doesnt work for reducing fat mass? :)

          • http://www.caloriesproper.com/ William Lagakos

            thanks for the insights. while I’m all for preworkout nutrition, I’ll be the first to admit it’s going to be highly individual-specific ymmv. IOW, I don’t think any theoretical benefits would outweigh getting consistently crappy workouts.

  • http://nigeepoo.blogspot.com/ Nigel Kinbrum

    “By the end of the study, they lost 2.5% body weight and 4% body fat.” Vice-versa.

    • http://www.caloriesproper.com/ William Lagakos

      57% of the weight they lost was fat mass, not LBM (Figure 1).

      • http://nigeepoo.blogspot.com/ Nigel Kinbrum

        Oops! My question still applies. Fat mass % loss was a lot higher than body weight % loss. I still don’t see where the 57% figure came from.

        • http://www.caloriesproper.com/ William Lagakos

          From Figure 1:
          0.8 kg fat loss / 1.4 kg BW loss = 0.57 or 57%. Total fat mass is less than BW, so changes in fat mass are proportionately bigger.

          • http://nigeepoo.blogspot.com/ Nigel Kinbrum

            Ah! I was confusing % changes with absolute changes. Thanks.

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  • davep

    Interresting article! Any recommandations for endurance athletes?

    • http://www.caloriesproper.com/ William Lagakos

      Hi Davep,
      No real recommendations, but I suppose it might be prudent to watch the timing of your fasts relative to training. IOW, do you perform better on a full stomach, after a 4, 8, or 24 hour fast, etc., etc.

  • thisisbetty

    Hi Bill! Do you have any thoughts on whether IFing for females is potentially problematic?

    Personally I feel great just eating when hungry which for me is kind of a late breakfast/lunch and then a decent sized dinner .. some days I’m hungrier that others and some days I eat earlier, but typically it’s a fast of 15 plus hours. (8pm to 10 or 11am)

    I’ve been trying to go to bed on a fairly empty stomach as I sleep better and I’m convinced that we burn off fat when sleeping and that the body can do other repairs and such better while asleep if it’s not having to deal with major digestion. (I know … my medical knowledge is stunning! : > )

    .. anyway I’m just curious what you think as I’ve seen some women say that they have real trouble trying to fast. Maybe it’s just that they take it too far and don’t eat when actually hungry.

    • http://www.caloriesproper.com/ William Lagakos

      Hi Betty,

      Thanks for the comment. It sounds like you have a great system that works well (if it ain’t broke…), especially because you “feel great.” With regard to gender-specific aspects of intermittent fasting, nothing comes to mind except that implementing an IF protocol seems highly dependent on things like lifestyle, work/class schedule, etc. However, there are probably experts on hormone cycles, eg, who might have something more insightful to offer (anyone care to chime in?). For example, I simply don’t know if different IF protocols work better on one hormonal landscape as opposed to another.

      all best,

      • thisisbetty

        Yes I do have something that works for me. I think that the concept of IF has helped me figure out when I have actual hunger (instead of just eating when I’m ‘supposed’ to) .. so I’m curious because I’ve heard some women say they have had negative experiences with it. thx much.

      • Sir Harrington

        there is very little gender-specific IF research out there.. maybe this can offer some hints: http://suppversity.blogspot.co.at/2013/06/ramadan-improves-body-composition-of.html

        • http://www.caloriesproper.com/ William Lagakos

          Thanks, Sir Harrington.

          thisisbetty, check out Adel’s article on IF – the main topic is Ramadan Fasting, but he discusses other research that might be of interest to you.

        • thisisbetty

          Thx Sir H (and Bill) … that’s a cool/interesting post. I’m still going through its links. : >

  • Rachel Gerson

    Have there been studies on if the subjects gained all of the weight back after ending their IF? I’ve played around with both IF and low-carb and in both cases have gained 100%+ the weight I lost when I began to eat 3 meals again.

    • http://www.caloriesproper.com/ William Lagakos

      No, but those studies would be great!
      My guess is that if the people went back to eating how they were at baseline, then their body weights would return to baseline levels as well.

  • Rod

    Great article. It seems to advocate eating once a day. That’s what I am headed toward as I am slowly inching back starting eating times. I really would like understand what effects working out has on fasted individuals. I will sometimes play 2-3 hours of basketball having not ate for 16 hours, at 42 years of age, and although I’m sore, there isn’t much of an affect. Should there be?

    • http://www.caloriesproper.com/ William Lagakos

      Hi Rod,
      Thanks. I don’t think fasting prior to bball should really cause any problems. You could always try a small meal prior to game time to see if it affects the soreness.

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  • Wenchypoo

    Question: should we be concerned with Dawn Phenomenon here, whether we’re diabetic or not? It seems the Warrior diet (done without the accompanying exercises) would feed into Dawn Phenomenon, but I’m just a curious housewife with a broken science bone.

    Other than that, I agree that it seems to be the most optimal way of eating. God knows it helps with the food budget!

    • http://www.caloriesproper.com/ William Lagakos

      Interesting. I don’t know. Meal composition might be a factor… if there’s no insulin surge and all of the other hormones are settled within a few hours, then maybe not. But if there’s a big insulin spike and some reactive hypoglycemia overnight, then you might wake with higher blood glucose levels… this is really all speculation, though.

      • Wenchypoo

        Thank you. I guess we’ll give it a whirl and see how we do.

        • http://www.caloriesproper.com/ William Lagakos

          Keep me posted!

  • zecg

    Great site, great content. I just wanted to root for my own team, which is team EOD. I’ve been doing a no-nonsense no-excuses strict EOD for 4 years now and the weight loss stops after some time (surprise!). So, now I’m oscillating between 67 and 72 kgs (stable for more than three years). Was 95-100 kg when I started, a (cheeso-)vegetarian for 15 years. I bicycle a lot, doing 32 km per working day (commute there-back) and 200, 300, 400 and 600 km brevets. In summer months, I do more than 2000 km per month.on bicycle, with a lot of climbing. Initially my protocol was quite strict, no eating two days in a row, which meant that I had to fast for two days if I wanted to switch days. But seeing as 600km brevets take 40 hours, I had to revise that. So now I eat during the ride if the ride is longer than 200km; otherwise, EOD restrictions still apply.

    There’s a few surprising things to recommend with EOD:
    1. less cognitive effort, no calorie counting, entire day free from thinking about food
    2. less sleep required on off-days; go to sleep at 1, still wake at 7 fresh and ready for breakfast.

    • http://www.caloriesproper.com/ Bill Lagakos

      thanks for the feedback. Congrats on your progress!

  • Colin P. Müller

    I’ve done the Warrior Diet for years, well before even knowing what IF was. It’s simply natural for me to consume all of my calories in a relatively short window. Despite a genetic propensity towards being obese, I’m fit and healthy without even putting in much of a effort.

    • http://www.caloriesproper.com/ Bill Lagakos