Let’s talk about calories. The backbone of the dieting industry.
What is a calorie... exactly?
“A calorie is defined as “the energy needed to raise the temperature of 1 gram of water by 1 °C”
So a calorie is a measurement of energy. A unit of energy if you like.
We use this measurement to determine how much energy is in food.
We worked how much energy we need to run our bodies
So obviously we can work out how much food we need to provide that energy to run our bodies….
And if we want to lose fat, we just need to eat less than we need to run our bodies
Seems easy right.
Well, it’s a little more complicated.
Let’s use a an electric kettle as an example
With the kettle, the energy in the form of electricity heats the water and then it comes out as steam.
Energy in-energy out
Calories in-calories out. Often known as CICO
That’s what the calories in calories out model would have you believe.
But...humans aren’t kettles.
We are complex creatures, maybe like a car than a kettle.
So lets move to the car analogy. Its not a perfect analogy but there are some similarities.
So this is a common questions
“How much should I eat to lose a kilo a week?”
Mathematician worked out that 1 gram of fat has an energy value of 4.5 calories so 1 kg of fat equals 4500 calories.
The thought was that if you reduced you daily calorie intake by 642.85 calories a day, you will lose a kilo week -Right?
Let’s use the car analogy.
The question could be “How much petrol will I need to drive 100km?”
Well according to the mathemeticians it will be 8 litres of fuel to drive 100 kms.
But we all know the answer is that it depends...
It depends on
These questions are all obvious right?
But yet we persist with the idea that as humans, we are more like a kettle than a car.
Energy in -energy out
Calories in -calories out.
The factor that makes us even more complicated than a car is our fuel system.
It is not a simple tank that just delivers what we need.
Our fuel is tightly regulated by hormones. They are involved in a complex feedback system where a change in one hormone causes a cascade of changes in all the other hormones.
Our body is regulated hormone receptors, not calorie receptors.
So what happens when you reduce your calories long term?
Well, interesting, (or shockingly) we have known for a very long time what happens when reduce our intake of fuel.
Our body reduces its output.
It reduces body temperature
It will slow its heart rate
It will slow down growth of hair and nails
It will feel lethargic
These is all part of our basal metabolic rate. The energy required just to run our body at rest.
All of this was demonstrated in the Minnesota semi-starvation study down way back in the in 1945.
The aim of this study was to document the effects of semi starvation (such as occurred in WW2) on human physiology and psychology and then the best way to rehabilitate them.
In this famous study they took 32 men.
For 3 months, they fed them 3200 calories a day, they exercised and they maintained their weight.
For the next 6 month they halved their calories down to 1560.
Now if you’re a seasoned dieter like I was, this sounded like quite a reasonable amount of calories. The diet was meant to mimic the diet of WW2 so it was largely carbohydrates, potatoes, bread pasta etc.- not much protein. The aim was for the men to lose 25% of their original body weight. As expected the men all began to lose weight. They still exercised. As time went on though, they needed to reduce their intake more and more to continue to lose weight. Towards the end of the study some men were in 400 calories a day.
Physically their basal metabolic rate slowed. They were tired, cold, hungry. Their heart rate slowed, they needed jumpers in summer. Their respiratory rate slowedTheir hair fell out.
Psychologically they became obsessed with food. It was the dominant topic of conversion. They would hoard recipe books. They were irritable, sometimes irrational and spent their time wishing this experiment to end.
Sounds alot like diet behaviour to me.
After 6 months, they went back to mormal eating. There was several arms in this phase but the most fascinating part of it is that then men regained all their lost weight with the resumption of normal eating. They then surpassed this number and gained more. They reported feeling fat.
And the birth of yoyo dieting begins..
This is why diets based on calorie restriction fail in the long term
The temptation is though to do it because short term it will work.
I hear this all the time
I just want to kick start my weight loss.
I need to lose weight by such and such date.
But the cost of this is reducing your mnetabolic rate for a very long time
So what the solution?
This has been the conundrum for people who have excess body fat to lose but are told dieting wont work.
The first step is to ensure the metabolic hormones are back in balance. Hormones like Insulin, Glucagon, Leptin and Ghrelin amongst others are often out of balance. That wonderful feedback loop we talked about earlier is broken. The driving cause is excess insulin in the body. Insulin is our major fat storing hormone and when insulin is high we become fat storing machines. Eat Low Carb Real Food.
The second step is intermittent fasting. High eating days and low eating days .
The body’s metabolism does not slow as it is not chronic calorie restriction. It is not the same amount of food each day. Some days you eat more, some days you eat less.
This should only be done once insulin is lowered and you have access to your fat stores.
Feasting and fasting.
Take care wonderful humans
Lucy and Mary
Dr Lucy Burns and Dr Mary Barson
Real Life Medicine