“Not all calories are the same” is a phrase you will hear more and more of as you progress with LCHF but what exactly does this mean?
Calories from Carbohydrates – Supply Based Energy
As discussed, consuming carbohydrates is an “inefficient” way for your body to obtain energy. Why? Because as soon as you consume them you create a blood sugar (insulin) spike in “unused” energy that MUST be converted to fat via lipogenesis and stored (weight gain). The degree of this spike varies according to the individual: age, fitness, carb tolerance, etc. but there will be a spike nonetheless and the weight gain is almost instant. Any energy that is consumed through carbohydrates is available at 4 kcal/g. Since the blood stream can only hold about 2000 kcal of glucose (cpl teaspoons of sugar), once this is depleted there is no energy left for the non-keto-adapted person and their blood sugar crashes. They then need to consume more carbs to increase blood sugar once again with associated glucose spike and weight gain. The cycle repeats over and over again with weight increasing all the time in a viscous cycle. Consider this to be a supply side form of energy, the control of which is haphazard, unregulated and limited i.e. highly inefficient.
Calories from Fat – Demand Based Energy
Now let’s consider the keto-adapted person whose primary source of energy comes from fat. For a start, fat has a calorific value of 9kcal/g, over twice as much as carbs! Further, when consuming fat there is virtually no blood sugar spike (weight gain), with stored “on-board” fat also being readily available. So what exactly does this mean in practice?
Consider a person of say 80kg in weight with 10% body fat composition. This means they have 8kg of body fat or 8000 x 9 = 72,000 Kcal of freely available energy, even without eating anything! Compare that to only max 2000 Kcal of blood glucose for the non-keto adpated person. Further, for the keto-adapted person the supply of energy via ketones derived from fat burning is one based on requirements i.e. demand, or regulated according to current energy requirements, with no blood glucose (insulin) spiking and associated weight gain. In fact the opposite is true; you will start to lose weight! Also, the keto-adpated person does not experience the large swings and crashes in blood sugar that the high carb individual does, with blood sugar remaining largely steady at all times. Consider this to be a demand side form of energy i.e. highly regulated and efficient.
So which source of fuel would you prefer??