Distinguishing between the effects of protein leverage and ketosis

ketosis
protein
proteinleverage
(Jack Bennett) #1

Consider a thought experiment of three different versions of a 2500 kcal diet (isocaloric).

SAD
50% carb - 1250 kcal / 313g carb
40% fat - 1000 kcal / 111g fat
10% protein - 250 kcal / 63g protein

"high-protein"
24% carb - 600 kcal / 150g carb
46% fat - 1150 kcal / 128g fat
30% protein - 750 kcal / 188g protein

ketogenic
5% carb - 125 kcal / 31g carb
65% fat - 1625 kcal / 181g fat
30% protein - 750 kcal / 188g protein

The SAD version of the diet has low protein and would likely create a lower level of satiety for a given calorie level.

This experiment is obviously artificial. In particular, the isocaloric assumption is pretty weak. Adding in substantial protein would probably lower total energy intake: if a hypothetical test subject is satisfied from 2500 kcal of SAD, they would probably be equally satisfied with a higher protein intake with lower energy.

I’m trying to pin down the key distinctions between the keto version and the high protein version. The protein leverage effect should be similar in both of those cases since the protein intake is now much higher in each case.

The main question on my mind is: how do we separate out the appetite-suppressing / satiety effects of (1) increased protein intake (protein leverage) and (2) ketosis?

I’ve done some searches on this but haven’t found any useful research into this specific question. Does anybody know of any work in this area?

(Bob M) #2

You’d also have to take into account the supposedly higher energy expenditure caused by higher protein:

I’ve seen short term (less than 2 weeks) studies, see Kevin Hall’s studies, comparing low carb versus lower fat. But I haven’t seen a more reasonable version, i.e., lasting longer than a month, to attempt to answer these questions.

(Jack Bennett) #3

Good point - the higher “thermic effect” of protein would be a real factor as well.

I think there are likely to be multiple compensatory and/or higher order effects that would come into play with those three radically different diets.

I came across some of Hall’s recent work in the area which is interesting. I wish that a group would do a nice long-term RCT to answer these questions.

(Bob M) #4

True. I was trying to find a protein study they recently did, and it might be the one I posted. However, I thought the study I was looking for used a cross-over design, where the participants ate one diet for a while (a week?), then ate a different diet for a week. (The study in the link I posted might be it - haven’t had time to read.) They basically replaced carbs with protein. But, now you have both reduced carbs and higher protein. Maybe it’s the reduction in the carbs that’s the benefit? Or the combination of the two?

I’d rather see two low carb diets compared, one higher fat, lower protein, and one higher protein, lower fat, with carbs the same.

(You've tried everything else; why not try bacon?) #5

So you are assuming that the amino acids from the protein in the diet would be metabolised, rather than used for structural (catabolic) purposes?

(Jack Bennett) #6

That’s a good question. I had always wondered how protein was considered 4 kcal/g when it was also used structurally. I think I asked the question here some time back and it was explained as mass balance of old proteins being recycled for energy.

(You've tried everything else; why not try bacon?) #7

The caloric content of foodstuffs is the amount of heat they give off when burned in a bomb calorimeter. This was all that could be measured a century and a half ago, before they even knew anything about the roles protein, fat, and carbohydrate play in human metabolism. So it’s actually quite anachronistic that we still use calories today to measure food input.

Proteins, interestingly, have a designed lifespan, which could be anything from a few seconds to several years, depending on the protein. And of course they get scavenged early if they get damaged (say from oxidation or such).

(Jack Bennett) #8

Agreed, the question seems far more complex than just “protein averages about 4 kcal/g”, because it’s not all used that way.

I would guess that some of the following things might be true:

  • After a workout, or during other anabolic activity, protein is used more structurally and less of it is burned for energy. So the protein consumed at that time might be “less caloric” because it’s used for building blocks. (It will also show up on the scale as “weight gain”: i.e. increase in lean mass.)
  • During autophagy, or other catabolic activity, protein is recycled and more of it is burned for energy
  • In the absence of dietary glucose (starch, sugar, etc), a larger fraction of dietary protein is used for the manufacture of essential glucose (i.e. gluconeogenesis). The protein used for this purpose delivers about 4 kcal/g of energy (the number on the label).

There are a lot of other hypotheses that you could come up with around protein. I’m curious to read more and find out which of them have been answered, and to what level of certainty.

(Bob M) #9

The research for protein to me seems like the more protein, the higher the energy expenditure, and the more muscle mass people either retain or gain.

Like anything else, though, the term “protein” is fraught with errors. For instance, Peter Ballerstedt shows how plant proteins are often “crude proteins” and these vastly overestimate the amount of usable protein.

For us meat eaters, it’s likely not a big deal, though if you’re using a program to track macros, you might want to toss any “protein” estimates from plants in the garbage bin.

As for gluconeogenesis and protein, that’s a tricky one. I doubt we know enough about it, especially for low carb people, eg, someone like me on this diet for 7 years.

(You've tried everything else; why not try bacon?) #10

My understanding is that the pathway that metabolises amino acids is so expensive of energy that if there is fat and carbohydrate to use instead, the body’s gonna use it. There are exceptions, of course: a small amount of amino acid is always being used for gluconeogenesis and making nitric oxide (from the liberated nitrogen), and in famine conditions, the body actually metabolises amino acids over fatty acids (to some extent) until quite late in the process (in late starvation, of course, fatty-acid metabolism regains its priority, which is why the Holocaust survivors were so thin when rescued). But in general, it is safe to say that amino acids are never metabolised unless absolutely necessary.

There is always a certain amount of proteolysis going on, because every protein has its lifespan (plus, some get damaged from oxidation, etc.), but the amino acids liberated from proteolysis generally enter the labile pool for re-use in making new proteins, instead of being metabolised.

I also question whether 4 kilocalories is actually the amount of energy liberated from amino-acid metabolism. Firstly, there is the energy cost of proteolysing a given protein into its component amino acids (likely not all that high, because it’s catalysed by a protease), and then there is a high energy cost to metabolising the amino acids (which is why they are usually either saved in the labile pool or excreted).

Also, the yield of ATP per molecule is not as large as the yield for glucose and fatty acids, and it’s ATP that actually powers the cells. To assess the energy yield of a macronutrient involves accounting for all the ATP consumed in handling it, plus all the ATP eventually generated by the end of the process. My impression is that it’s a lot more complicated than assuming that the energy yield is simply the heat derived from burning the macronutrient. For this reason, I kind of wish that the bomb calorimeter had never been invented.