I haven’t posted recently due to a busy easter period but the next article is a continuation of a series of posts on fat loss and removal. Fat loss is not just about doing lots of activity or going to weight watchers. It involves a number of complex processes that will result in a net burning of “fat.” It highlights why a bad diet doesn’t result in fat loss even if training regularly. It also highlights why fat reduction is reduced if activity is not prioritized.
Although I may be stating the completely obvious removing fat from fat cells so it can be used as energy is the emphasis of burning body fat.
The speed of this depends on the activity of hormone sensitive lipase (HSL) (which is partly regulated by the hormones insulin, testosterone, cortisol, estrogen, growth hormone and the catecholamine’s epinephrine and noradrenalin).
Primarily the catecholamine’s (transported in the blood) activate HSL in turn breaking down fat cells in to glycerol (a carbohydrate) and three fatty acids (the catecholamines include noradrenalin commonly referred to as adrenalin).
Glycerol can be used for energy as a carbohydrate; fatty acids can also be utilized for energy though interestingly they can also be restored by the body as part of a fat cell if not burnt as energy.
This process is called (re-esterification) which may happen if blood flow is sluggish.
The key regulator of HSL is a compound called cyclical adenosine monophosphate (cAMP).
When this is in abundance fat oxidation is increased.
In turn elevated insulin (which typically increases when carbohydrates are consumed) lowers cAMP slowing the rate of fat mobilization. cAMP is increased or decreased when the catecholamine’s bind to adrenoreceptors depending upon what receptors they bind to.
The two most important adrenoreceptors are beta 2 receptors (which will promote cAMP levels) and alpha 2 receptors (which will decrease cAMP levels).
As you can see catecholamine’s can promote and inhibit fat mobilization, though this is dependent on the other relevant relative hormone activity and the proportion and distribution of both types of adrenoreceptors in the body as to if there will be a net increase in fat mobilization.
As you can see at a cellular level there are a number of factors that increase or limit fat burning- focussing upon one part of this process does not necessarily mean long term fat burning- in fact it could mean the opposite.
With increased blood flow from increased activity the free fatty acids will bind with a substance in the blood called albumin and are transported around the body.
When energy is demanded by tissue such as muscles or the liver the free fatty acids can be burnt as energy after being transported in to the mitochondria (where energy is produced) helped by an enzyme called carnitine palmityl transferase (CPT).
CPT activity is moderated by your aerobic capacity and muscle glycogen levels- this indicates that that improved aerobic fitness is an advantage when looking to burn fat as well as glycogen depletion (minimizing the amount of stored carbohydrate in the body).
So what are the takehome points from this (obviously it may need a rereed- but if you can not be bothered then this is a shorter format).
Activity stimulates fat breakdown, energy demands will dictate how and where this fat is burnt, when dietary carbohydrates are low then fat burning is prioritzed). Exercise intensity needs to vary to alter the hormonal stimulus relating to fat burning though your fitness levels will dictate your fat burning “potential.” Simple!
IanMellis.com 