Is Calories In – Calories Out really right?
We have discussed before the “myth” of calories in – calories out. This is the outdated fitness concept that losing weight is based on burning more calories than you consume and reduces the entire process to little more than a math equation.
As I’ve noted in this post on basal metabolic rate our body is a dynamic system and it makes adjustments to the “calories out” variable when the “calories in” variable is changed. One half hour on an elliptical machine doing cardio maybe consumes about 200 calories. Then at work your co-worker brings homemade chocolate chip cookies, and your small two cookie indulgence just added 160 calories! This is a no-win game.
Fortunately, the model described above is definitely not the way this works, especially if you are doing more intense intervals of exercise.
The Real Metabolic Effect of Intense Exercise
In the video “Sugar – the Bitter Truth“, Dr Robert Lustig discusses the true metabolic effect of exercise beyond the calories expended during the activity itself. I would add that the more intense the exercise, the more pronounced these effects are. The three effects Dr. Lustic mentions are:
A – Exercise of the muscles decreases muscle insulin resistance. Your muscles prefer glucose as fuel and quickly deplete the glycogen (stored glucose) in the muscle during exercise. This depletion signals the insulin receptors on the surface of muscle cells to upregulate so that the presence of blood insulin (which coincides with dietary glucose intake and availability) stimulates the GLUT-4 transporter on the cell membrane which allows the muscle cells to bring glucose in from the blood and rebuild these glycogen stores, as well as being converted to energy production if the muscle is still being exercised. Metabolically, excess insulin stimulates fat storage, so the more insulin and glucose taken up by the muscles, the less tendency there is for fat storage.
B – Exercise reduces stress hormones. This is a really complicated subject, as cortisol is the major stress hormone and is actually increased as a result of intense exercise – this could be a bad thing if not managed since cortisol is a catabolic hormone (breaking down muscle protein) which also can increase fat storage. The key however is to consume adequate nutrition post-workout to release insulin, which then negates the cortisol, and of course becomes anabolic and stimulates muscle growth. Muscle growth is not cheap metabolically and will consume calories as it continues through the next few hours and at some level beyond. The real beneficial effect of exercise on cortisol however is the fact that exercise tends to release your pent-up low-level mental stress through the release of dopamine (those feel-good hormones) which can help relieve that all day long elevated cortisol.
C – exercise increases the speed of the Kreb’s cycle in mitochondria (aka metabolism). The mitochondria are small organelles in the interior of cells which are responsible for taking the macro-nutrients which come into the cell and converting them into energy by using a chain of enzymatic reactions known as the Kreb’s cycle to create ATP. Excess macronutrient which exceed the capacity of the Krebs cycle are discharged as citrate, which is eventually converted to fat storage. The stimulation of the muscles and the increased demand for energy generated by exercise is like turning up the thermostat on the mitochondria – the mitochondria adjust by increasing energy output through speeding up the Krebs cycle. A faster Krebs cycle means less citrate bypass which means less substrate for de novo lipogenisis (creation of fatty acids) which ultimately are stored as fat tissue.
Other Hidden Benefits to Exercise
There are of course other beneficial health effects which happen as well, I will post more in the future, but if you are interested check out this article in the meantime.
So, do not pay a huge amount of attention to those little calorie counters and focus your exercise instead on creating intensity which will generate these metabolic efficiency benefits. This is what will raise your Basal Metabolic Rate (i.e. boost your metabolism) and result in increased calorie consumption through the course of the day. That is the true benefit of exercise, not how many calories you burn while exercising.