Until this weekend.
I’ve been reading an interesting book called Trick and Treat by
Barry Groves. For the first time I understand the science (and therefore the falsity!) of the calories in, calories out theory.
So, in my words (and some of his) here’s the nub of it. Please bear in mind that I’m no scientist (which incidentally doesn't make me any less 'qualified' to be an expert about my relationship with food and my body).
This is my understanding of his explanation, of the way it works and it may not be 100% correct… or the way I have explained it may not be completely clear and concise (I’m not one for being concise!). Anyway, here’s what I’ve understood, which I think is a good starting point . If you’re interested, his book is well worth a read.
What is a calorie?
A calorie is a unit of heat.
How are calories measured in food ?
By burning the food in a device called a ‘bomb calorimeter’ and measuring the amount of heat it gives off.
A BOMB CALORIMETER
1 gram of carbohydrate burned in a bomb calorimeter gives an energy value of 4.2 calories
(Groves says it’s actually kilocalories but for the purposes of this post I won’t go there).
1 gram of protein gives 5.25 calories - but you have to take 1 calorie away because protein doesn’t oxidise properly (not sure I quite get that bit but let’s go with it!)
1 gram of fat gives 9.2 calories
Round these up to the nearest whole number and you get:
Carbs 4 cals
Protein 4 cals
Fat 9 cals
These are the figures that are used in calorie charts to work out how many calories there are in various foods .
There are two flaws in this system.
Flaw number 1
Our bodies do NOT burn food in the same way as they are burned in a ‘bomb calorimeter’. (No? Really!)
Our digestive process, unlike the bomb, is pretty inefficient. In our bodies, the chemical process which oxidises sugar to provide energy produces carbon dioxide. About half is exhaled when we breathe, the other half is excreted in our sweat, urine and faeces as energy containing molecules - so the energy value which we lose this way needs to be taken away from the original food intake…
With me so far?
Surinder Phul (www.eatwell.co.uk) a very wise nutritional therapist who we spoke to about calories and other things when we were writing Beyond Chocolate, wasn’t wrong when we asked her…
“We know the calories in calories out theory doesn't work… but we don’t understand why, can you explain?”…
She took a deep breath and said…
“We’ll, it’s that… the way it works is...it’s… complex…”
And that was about it!
It’s complicated and complex but not impossible to get your my around.
So here goes.
Flaw number 2…
The body does not use all the food we eat to provide energy.
That strikes me as important - the body DOESN’T use all the food we eat to provide energy.
For example, the main function of protein in our diet is to build and repair cells, not to provide energy. So, (and I’m cutting the explanation down a bit here) meat contains about 23 grams of protein per 100g, a person who weighs say, 70 kilos, needs to eat about 300g of meat (or equivalent other protein) just to supply her basic protein needs (presumably to keep her cells in good order of repair?). If she ate that as lean chicken that would be about 465 calories. These calories are NOT used to supply energy, so they would have to be deducted from her total calorie intake…
Much of the fat we eat is also used to provide materials used by the body in processes other than the production of energy. I’m fascinated by this science! Fat is used in the manufacture of:
Bile acids (any of various steroid acids, produced in the liver and stored with bile, that emulsify fats during digestion).
Prostaglandins (any of a class of unsaturated fatty acids that are involved in the contraction of smooth muscle, the control of inflammation and body temperature, and many other physiological functions.
Prostacyclins (a type of prostaglandin that is a metabolite of arachidonic acid, inhibits aggregation of platelets, and dilates blood vessels).
Leukotrienes (produced by white blood cells in an immune response to antigens, that contributes to inflammatory reactions.
Thromboxanes (cause constriction of vascular and bronchial smooth muscle, and promote blood clotting)
Hormones (any of various internally secreted compounds, such as insulin or thyroxine, formed in endocrine glands, that affect the functions of specifically receptive organs or tissues when transported to them by body fluids.)
And there is more, but I’m starting to get the picture…
The way our bodies use food is indeed complex and to me, quite fascinating.
All the calories that are used for the processes above also contribute nothing to energy production and so must be deducted from our total calorie intake when we talk about calories in calories out.
Trying to work out how much energy the food we eat actually produces and how much of it will be stored as fat, without the above information, gives a very inaccurate answer and so it’s a waste of time… incredible given that it’s the foundation of almost every diet and healthy eating plan known to woman!
And there’s another thing…
We are told by ‘experts’ that a calorie is a calorie. That all calories were created equal. What they mean by that is that two diets made up of exactly the same number of calories but totally different foods, will lead to the same amount of weight gain or loss. Over the past century many diet studies how found that this just is not true!
Some studies have shown that high fat diets are much better at reducing weight than low fat diets (I’m not advocating ANY kind of diet here, just reporting the data as I’ve read it).
And these ‘experts’ criticise the findings saying that they can’t be true because that would violate the laws of thermodynamics… apparently.. Funnily enough, I think the experts might just be the ones who are wrong… again.
This narrow view of calories in calories out may well comply with the first Law of Thermodynamics but not the Second Law.
So, here’s a hopefully brief expo on laws of thermodynamics!
1st Law is a conversion law.
2nd Law is a dissipation law.
It’s the second law which governs the use of energy in chemical reactions within our bodies.
Here’s the analogy that Barry Groves uses in his book:
The energy in the petrol that you put in your car, makes the car move but it also produces heat through friction and noise, which is wasted energy.
The 2nd Law is all about efficiency. How much of the energy that we put in does useful work and how much is wasted?
Although all the energy in the petrol is accounted for and complies with the 1st law (in other words it is all converted to energy), the moving car itself, if the waste products (heat & noise) are removed from the equation, does not comply with the 1st law.
The second law was developed in that context - in other words it was developed to account for the inefficiency of machines (like our bodies!). The 2nd Law says that no machine is completely efficient.
Inevitably some of the available energy from the food we eat is is lost as heat or in the internal rearrangement of chemical compounds and other changes. And as different foods use different metabolic pathways, with different levels of efficiency, there will of course be variations in the level of efficiency in different foods. Therefore the idea that ‘a calorie is a calorie’ violates the 2nd Law of Thermodynamics as a matter of principle.
Our bodies do not use all calories in the same way.
Surinder did say it was complex.
So, where does that leave me?
Well I finally understand that:
Not all calories are burned by our bodies to create energy.
That some of the energy that is produced cannot be used up by things like exercise - it's wasted in various ways.
That our bodies use different foods (and their calories) in different ways and for different functions.
That eating fat doesn't make you fat.
That eating fewer calories doesn't automatically (and for the long term) make you thin.
It leaves me convinced that counting calories is an unhelpful and misleading and that diets based on calorie counting have positively contributed to weight gain for hundreds of thousands of women. By treating all calories as equal, by trying to limit calorie intake without understanding how they work, by not tuning-in and eating according to out hunger and satiety, we have been sold false truths. False truths which have a VERY high price. Overeating, poor food choices and obesity. We have been treating 300 calories of, let's say pasta as exactly the same as 300 calories of butter and yet they are used in completely different ways by our bodies. One produces energy one does not.
I have a fantasy that the powers that be have coined this ‘calories in calories out’ phrase because they think it’s a simple, scientific sounding way of saying to people ‘eat less, move more’. Ever heard that one? Both are simplistic, misleading, patronising and ultimately useless. We are not stupid. I wish I’d been taught more about how my body works in science lessons at school and less about how plants photosynthesise. I am fed up of being patronised. Of course overeating leads to weight gain. And trying to stop us overeating by having us count how many calories we consume is clearly not the way! If it were we'd all be slender, fit and healthy by now. Not more overweight than we have ever been (as a nation).
Information is power. When I understand what goes on in my body, it helps me make choices that feel right and that make a real difference.
It’s time we stopped talking calories!
For quite a while after I stopped dieting I would still find my eyes straying to the calorie count on the back of packets. I found one way to stop that, I reduced the amount of packet food I bought :-)
And I created a mantra for myself… calories shmalories… I’d say it to myself every time…
Until I stopped thinking that way and started seeing food as food. Food I like or don’t like, food that I feel like eating or don’t feel like eating, food that I think of as healthy and nourishing and food that I think of as tasty but empty of nourishment, food that leaves me hungry again very soon after I've eaten and food that satisfies me for a while, food I crave and food I want and enjoy (and the wisdom to know the difference…)
The more I understand the more I am inspired to find out more about how my body works and what it needs, by tuning in, by listening, by reading more inspiring books.
Are you a calorie counter? Or have you been in the past?
What do you think of all this?
I’d love to know!