Monday, January 11, 2010

Paying the energy bills.

People have asked me whether having cut calories back when trying to lose weight it is important to compensate for additional calories that have been ‘spent’ through exercise.

Firstly let me make it clear if your body needs say 2100 calories a day to live and allow you to do all the things you are asking it to do (run your brain, breath, move, digest food, eliminate that food, constantly re-build cells etc. etc.) and you only give it 1100, it has to have that energy from somewhere. It runs contrary to the laws of physics for it not to have to take that energy from somewhere.

So in ‘the economy’ of your body evolution has coded three different types of energy, that which you are earning and processing, a i.e. your food intake in it's various forms which it always uses first, the energy involved in your active infrastructure (muscles, skeleton organs etc.) and that which it has stored in the bank against hard times – fat..

Fat is natures energy store. Every gram contains 9 calories as opposed to 4 in every gram of protein or carbohydrate. It is (as far as survival goes) like gold.
So why not if we have too much just eliminate it out of the poop chute?
The reason is that we evolved in a world where food supply was not constant and in winter particularly, those who had been able to store up excess energy from the plentiful times had a greater chance of survival (and therefore were more likely to re-produce) than those who could not.
There was no advantage to be had in getting rid of precious energy you may need during the hard times. It is this evolutionary fact (which we see in operation in many many other animals), that gives us the problems we now have.

The difficulty we now face is that we now have no times of famine (well most of us do not) and we are surrounded by shelves of supermarket groaning with energy dense foods. Trouble is evolution is glacially slow and ours has not had time to adjust and has not yet caught up.
So back to the original question. Let us suppose you embark on a sensible calorie restricted diet where the intake needed to maintain your body and the activities you are doing is 2100 and you aim for a loss of say 2lb per week aim to take in 1100 calories per day. This is quite a drastic change from the say 2500 per day you were consuming.

Being dedicated and focussed you take yourself off to the gym and having strapped on your trusty heart rate monitor you exercise to the tune of 600 calories. In effect you have just robbed you body of 600 calories as your normal maintenance level has gone from 2100 to 2700.
This is something of a shock to your system as you are now actually 1700 short on the day.
Now unfortunately as yet the body has not evolved a direct line from your conscious mind to your cybernetic regulatory system. It is no good saying don’t worry I am only doing this for a week or two, feel free to use up my fat stores normal service will be restored as soon as I am X stones Y pounds.

What your ‘evolutionary body thinks is “cripes! The food (income) has run out I have energy bills to pay (the deficit you have created) and I have to pay it and quickly."

Now (aside from where it is needed to perform certain functions in the body like protect nerves etc.) fat really only has one main purpose and that is paying the energy bill. But it is very good at that. However it is not the only substance in your body that can pay the energy bill. Your muscles, organs and skeleton can too.

But let us look at muscles for a moment. In evolutionary terms these are the earning sections of your economy. They allow animals to run, jump, walk to where the food is, to hunt food down, lift rocks and branches to find grubs etc. So while they can pay energy bills they can also be employed to keep the income coming in - call it your earning infrastructure.

We know that if you work muscles with physical exercises and particularly heavy weight exercises your body would rather repair them and keep them in good working order than it would use them to pay the energy bills. Of course it would if they are there you can eat if they are not you cannot.

This makes evolutionary sense. Those early humans who had the muscle power to hunt and gather, got more food than those who did not.

Consequently your body responds differently to say a 1000 per day deficit if you are accounting for and eating those additional calories than if you are not. It registers that the muscles are being used that energy volumes are increased even though there is still a deficit. Exercising and increasing intake is sometimes called 'high energy flux'.

What we know is that if you are in high energy flux and your deficit is the same as if you were just in calorie depravation your body reacts differently.

In high energy flux your body knows it has to maintain it’s investment infrastructure (the muscles and skeleton etc) as they will be needed to keep the income flowing in therefore it pays the energy bills out of it’s fat reserves.

If you force it into what is sometimes called ‘starvation mode’ by going on very low calorie intake (wether by choice or by creating that state by exercising and not increasing intake) it tries to hang on to it’s ‘gold deposit’ of fat as it has no idea how long the famine will last and after all it is not using it’s infrastructure anyway so it can sell a bit of that off.

What does this mean to people trying to lose weight? It means that if you send your body into energy deficit but do not use your infrastructure you lose a higher proportion of muscle than you do fat. This in turn decreases the need for calories (after all the investment infrastructure cost more to maintain than the fat deposits) which makes sense really seeing as there is a shortage of food. Thus decreasing your need for energy.

You will lose weight by starving! But what happens when you have had enough of starving yourself and the will power goes? You have sold off some investment infrastructure (muscle and skeleton) and the amount of energy you need to stay alive has fallen from say 2100 calories per day to 2000.

But no body gives you an accurate read out and you return to your previous eating habits and consume 2500 calories a day. So even though you have lost weight you are now putting it back on at a rate greater than you were before because the level needed to maintain your physical body has fallen. So now rather than being in excess to the tune of 400 cals per day you are in excess to the tune of 500 calories per day.

Not only that but unless you make efforts to re-build that investment infrastructure that excess will be laid down against either another famine or when you next decide to go on a starvation diet. No wonder the fat piles back on.

If you are looking to lose fat, strive for a state of high energy flux. Let your body know it needs all the infrastructure it has to maintain these levels of energy input and let it be confident in using up some of it’s fat stores. That way lies the lean fit you I suspect you want!


  1. I thought you were offering to pay mine for me - last winters came in at over £600 when I saw your title x

  2. I am not even thinking about what mine will be, not only that I don't have the insulation on my bod I used to have!