The FastDay Forum

Dr M put up a post on 22 Feb 2013 here addressing the question 'Does intermittent fasting lead to muscle breakdown and protein deficiency?' and concluding 'No'.

But he points out that he personally never goes without food for more than 12 hours (something he repeated in the ABC TV clip). 'If your protein intake is adequate, and we actually recommend an increased protein intake on fasting days, then you are not going to get “muscle protein breakdown”.'

Dr M put up a post on 22 Feb 2013 here addressing the question 'Does intermittent fasting lead to muscle breakdown and protein deficiency?' and concluding 'No'.

But he points out that he personally never goes without food for more than 12 hours (something he repeated in the ABC TV clip). 'If your protein intake is adequate, and we actually recommend an increased protein intake on fasting days, then you are not going to get “muscle protein breakdown”.'

I'd been saving all my calories for the evening, but on reading that post I decided to start having a "breakfast" on my fast days of a small tin of tuna with some lime juice. This works out at about 70 calories but with 15g of protein, leaving me plenty of calories left for my evening meal but hopefully smoothing out my protein intake.

Thanks for that. I did some searching on http://caloriecount.about.com and it does seem that tuna is about the purest protein you can get in a natural product, which means it is the least calorific way of getting protein on a fast day. Half a 'normal' tin (about 70g drained) is about 70 calories and 16.3g protein: 93% of the calories are protein. Not much of a vegetarian/vegan option of course...

I confess I am a teensy bit concerned about this protein issue and how much we should be getting on fast days and the maximum period we should go without it. (Protein, that is... )

[carorees]

Oh, that might well be why. It does seem to be a bit cautious though, after all one day without 45-65g of protein is hardly going to cause all your muscles to atrophy? And isn't that what autophagy is for anyway to do a bit of dismantling old worn out parts and recycling them into new shiny bits?

Any comments on my thesis above that going a bit under your daily protein needs on two days is hardly going to cause much damage? Am I missing something?

Any comments on my thesis above that going a bit under your daily protein needs on two days is hardly going to cause much damage? Am I missing something?

Nope, Varady's sub 30g ADF trials do not identify any issues.

At 500 cals with a "normal" protein as a % of cals the protein would be perhaps 18 to 44g (15 to 35%).

People are generally knitting smoke when advocating higher protein levels, let's see evidence !

Some research here: http://www.ncbi.nlm.nih.gov/pubmed/9665093 - referenced by Wikipedia.

As Dr M points out, the evidence from Dr Varady supports the contention that IF leads primarily to fat loss. It remains an open question (to me, anyway) whether a slightly longer 'total' fast of say 20 hours is a good thing (as might be inferred from the work of Dr Longo [reduced IGF-1] or Dr Mattson [cellular stress]), or potentially damaging for muscle mass (per Dr Lau). Dr Mosley does seem to be hedging his bets on this one a bit by stressing that he himself never goes more than 12 hours without feeding.

[We have drifted away from the original topic of TDEE onto the topic of protein on a fast day, do we need this moving onto a new topic?]

[carorees]

Done!

http://ajcn.nutrition.org/content/81/1/69/F1.medium.gif

True fast - zero food for 36 hours alternate days. Average weight loss 1.4kg of which 0.6 kg was FFM (which includes water etc).

"Significant reductions were observed in fat mass (P < 0.001) and fat-free mass (P < 0.05) after the intervention"

Suggests you won't waste away on low protein even with 36h fasts. BMI of the males was 25 and females 22.5 so may not be representative of overweight / obese subjects.

Thanks Phil (for anyone else: the original paper is at http://ajcn.nutrition.org/content/81/1/69.full), but not sure I am much wiser.

0.6kg loss of fat-free mass seems significant (43% of total weight loss), but OTOH if it includes water it is pretty meaningless.

FFM always includes water, you have to do nitrogen balances to estimate muscle protein loss.

The typical assumption of 3500 cals/lb assumes about 75% fat loss as fat is itself 4086 cals/lb.

Unfortunately it seems to me the scientific answer to the question of what impact intermittent fasting has on muscle loss through protein deficiency is 'no one knows - yet'. In particular the question of whether a longer fasting period (within the say 36-hour maximum fasting window) might result in increased muscle wastage. Hence, I think, Dr M's caution about keeping up protein levels on a fast day and his personal preference for taking in some food (i.e. protein) at least every 12 hours.

http://www.ncbi.nlm.nih.gov/pubmed/22889512 showed a non-significant fat free mass gain using only 15% of cals as protein with 25% of TDEE calories on alternate days fasting. They ate at lunchtime, so this contrasts the one above and suggests eating something with <30g of protein avoids FFM loss in ADF in obese women.

Great catch Phil! This seems to be the research from Dr Varady that Dr M has referred to. Sounds like you have read the paper not just the abstract? So on fast days what exactly did the subjects eat and when (esp. protein)?

It's in the IF trial summary sheet (row 13) - lunchtime meal at 15% protein.

From memory it was the same meal plan as at http://ajcn.nutrition.org/content/90/5/ ... nsion.html - will check later...

All subjects consumed 25% of their energy needs on the fast day (24 h period), and 125% of their energy needs on the feed day (24 h period). Subjects were provided with 3 calorie-restricted meals on each feed day and one calorie restricted meal on each fast day. The feed/fast days began at midnight each day. Fast day meals were consumed between 12.00 pm and 2.00 pm to ensure that each subject was undergoing the same duration of fasting. The feed day meals consisted of a breakfast (1/3 of daily calories), lunch (1/3 of daily calories), and dinner (1/3 of daily calories). Subjects were instructed to consume the entire breakfast meal between 6.00 am and 8.00 am, the entire lunch meal between 12.00 pm and 2.00 pm, and the entire dinner meal between 6.00 pm and 8.00 pm.

Composition data per 2000 calories :-

Code: Select all

Table 1. Nutrient composition of the ADF-HF and ADF-LF diets.a and b

Nutrients   ADF-HF   ADF-LF
Total fat (g)   100 (45%)c   55 (25%)c
Saturated fat (g)   30 (14%)c   13 (6%)c
Monounsaturated fat (g)   45 (20%)c   30 (13%)c
Polyunsaturated fat (g)   25 (11%)c   12 (6%)c
Trans fat (g)   0   0
Cholesterol (mg)   328   112
Protein (g)   75 (15%)c   75 (15%)c
Carbohydrate (g)   200 (40%)c   300 (60%)c
Fibre (g)   27   27

I was under the impression that we only need around an ounce of protein a day. That's all the body metabolises. It's an eighth of a chicken breast. Why is everyone so worried about their protein intake? I can't imagine any diet where you would be deficient under normal circumstances. Please explain.