Protein Shakes, and the Calorie Nonsense

[Snypa]

"I count it as "energy value of protein assimilated" + "energy cost of assimilation" = calories used" I agree, it appears a very reasonable argument. This is not what I'm debating however:


calorie data given in nutritional tables are derived from bomb calorimetry data (e.g. when we combust it in the flow of oxygen, this is how much energy we get out). this ONLY really coincides with the energy we get by digesting protein for energy- not the energy associated with building tissue etc.

I hope this makes more sense, maybe lack of clarity in my argument was leading to confusion.

[NU_nutrition_TS]

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"the calorie value on protein is still valid"
leap haha. Being that you are implying (by mistake perhaps) that this value is equal to the value of energy required to maintain the tissue. Protein has a calorific value, in all respects, however the debate is whether the combustion values are the same as the bio-utilised amount.

Couldn't agree more with this. This is what really does my head in - food is not combusted in the human body like it is in a bomb calorimeter (the former is chemical energy production in an open system while the latter occurs in a closed system), yet people still insist on equating the two! A bomb calorimeter is a much more efficient fuel 'burner' than is the human body. With the conversion of most macros into ATP, the efficiency is below 40%.

It makes a refreshing change to have someone who is well-versed in the science wade in on this perennial 'old chestnut'!

[Elvis]

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calorie data given in nutritional tables are derived from bomb calorimetry data (e.g. when we combust it in the flow of oxygen, this is how much energy we get out)..

absolutely, my background is chem. eng. so I'm well aware

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this ONLY really coincides with the energy we get by digesting protein for energy- not the energy associated with building tissue etc.

building tissue is two things it is depositing material with a calorific value and it is powering the chemical reactions required to achieve this, I don't see your distinction, unless you are saying the energy requirements of this work is significantly different in efficiency to other metabolic processes

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I hope this makes more sense, maybe lack of clarity in my argument was leading to confusion.

no, but I will happily concede if our diet does not allow us to be anabolic we probably require less calories

[Elvis]

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With the conversion of most macros into ATP, the efficiency is below 40%.

surely what matters most is if it is significantly different macro to macro, if it's a consistent error it's not such an issue

[NU_nutrition_TS]

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surely what matters most is if it is significantly different macro to macro, if it's a consistent error it's not such an issue

It's not an error it is a fact - if you consume 100 kcals of carbohydrate you make around 40 kcals worth of ATP, which is the actual 'fuel' your body uses. When your muscles use that ATP to contract and do work it is itself very inefficient.

When you come to storing 'excess calories' as fat you have to convert them into fatty acids and glycerol and connect each of three fatty acids to a glycerol molecule - this is the synthesis of a larger molecule from smaller units (anabolic) and the whole process requires energy to accomplish. So 100 kcals worth of excess food is not going to be stored as anywhere near 100 kcals worth of body fat. Which makes the whole calorie counting exercise a complete nonsense!

[Elvis]

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Which makes the whole calorie counting exercise a complete nonsense!

do you mean exercise as in on a treadmill or as in the process of adding up calories consumed?

[NU_nutrition_TS]

Both! Calories used in exercise vary with the age, basal metabolism and current bodyweight/composition of the person performing it, ambient temperature and many other factors. So a book of tables or a readout on a piece of exercise equipment tells you very little about how much energy you are actually using during any activity. Further, for most activities, the amount of calories you are likely to use is insufficient to cover even a small snack - and most people engaging in exercise a) find their appetite increases and b) they assume it will safely allow them a small snack as a reward for their hard work!

We have already seen how inefficient the human body is at converting the energy in food to usable ATP energy in the body and converting that energy to useful work. Taking these together, the whole notion of calorie counting and balancing is, at the very best, a very rough and constantly shifting/adapting guide to proper weight/body composition management.