By Dr. Haran Sivapalan
It’s tempting to dismiss cycle commuting merely as a way of logging junk miles. Cycling to work, to the shops or on the school run, however, affords a lot of health benefits. Earlier this year, a meta-analysis of over 45,000 people found that those who commuted by bicycle enjoyed leaner body composition, better cardiorespiratory fitness and healthier blood lipid levels. With regards to this latter measure, commuters had slightly lower levels of a particular type of blood fat – triglycerides. This is of interest because, depending on our genetics, some of us are more susceptible to high levels of blood triglycerides, which in turn can increase our risk of weight gain, diabetes and heart disease.
What are triglycerides?
Triglycerides are the most common type of fat in the body. In terms of chemical structure, a triglyceride molecule is composed of glycerol and fatty acids. As you may recall from Do Your Genes Help You Burn Fat? blog, fatty acids are a good source of energy. Accordingly, triglycerides, which are a rich source of fatty acids, are useful both as a fuel for exercising muscles and as an energy store (in fat or ‘adipose’ tissue).
Why are high levels of blood triglycerides bad for our health?
High blood triglyceride levels are associated with an increased risk of weight gain, obesity and Type II diabetes. This is because excess triglycerides are likely to be stored away as visceral fat tissue (hence weight gain and obesity), which can impair our sensitivity to insulin (hence the Type II diabetes).
High levels of triglycerides are also linked to heart disease. To understand why this is the case, we first need to get our heads around how triglycerides are transported in the bloodstream.
Triglycerides are not soluble in water, so they have to be carried around in special particles called lipoproteins. When we eat a fatty meal for instance, we package triglycerides along with another fat-like substance, cholesterol, into lipoprotein particles called chylomicrons. These particles then transport triglycerides to be used by other tissues, such as exercising muscles, or to be stored in adipose tissue.
Our liver also makes triglycerides. Triglycerides produced by the liver are packaged along with cholesterol into lipoprotein particles called VLDL (Very Low Density Lipoprotein). VLDL particles are then released into the bloodstream, again for their triglycerides to be used by other tissues.
With the above in mind, a high blood triglyceride level essentially means we have lots of lipoprotein particles, laden with triglycerides and cholesterol, circulating through our bloodstream.
As our body metabolises and uses the triglycerides within these lipoproteins, however, it leaves particles that largely contain cholesterol. Some of this cholesterol is subsequently taken up by white blood cells and is deposited in fatty plaques within the linings of our arteries. These fatty plaques, called atheromas, can then obstruct blood flow to vital tissues, starving them of oxygen. When this occurs in the coronary arteries supplying the heart, we describe it as heart disease. Overall then, by stimulating the deposition of fatty plaques in our arteries, chronically high blood triglyceride levels increase our risk of developing heart disease.
How do our genetics affect triglyceride levels?
As well as containing triglycerides and cholesterol, lipoprotein particles carry specialized proteins called apolipoproteins. These regulate the transport and metabolism of the lipoprotein particles and their contents, and therefore influence the levels of cholesterol and triglycerides circulating in our bloodstream.
One apolipoprotein in particular, ApoA5, helps to lower our blood triglyceride level. It’s still being researched, but it’s thought that ApoA5 inhibits the production of certain lipoprotein particles, while also stimulating the breakdown of triglycerides within these particles.
So, how do genes fit in? Variants of our APOA5 gene, which encodes the ApoA5 protein, affect the activity of ApoA5, thereby influencing our blood triglyceride levels. Moreover, APOA5 gene variants have also been linked to differences in our risk of obesity, Type II diabetes and heart disease, all of which are related to high triglyceride levels.
Depending on which APOA5 gene variants we inherit, we may need to be more mindful our blood triglyceride levels.
How can cycling help?
Exercise is a great means of lowering your blood triglyceride levels.
While all exercise tends to be beneficial for your blood lipid profile, studies suggest that, with regards to aerobic exercise such as cycling, more intense activity is related to greater reductions in blood triglyceride levels. If you’re specifically looking to reduce your blood triglyceride levels then, it may be wise to include high-intensity sprint intervals and hill sessions in your training.
By contrast, volume seems to be the key as far as resistance training is concerned. When you’re in the weight room, a high number of sets and reps (as opposed to a high-load, low rep approach) has a bigger impact on blood triglyceride levels.
From a coaching point-of-view, the knowledge of whether you are genetically likely to have a higher level of blood triglyceride levels, can help us tailor your training even greater.
To quote the great Fausto Coppi “No hour of life is lost that is spent in the saddle”. “Ride your bike, ride your bike, ride your bike”… if you are riding then you are progressing…improving and burning calories simple…
Rides to work can be mixed up with sprint, threshold, tempo and endurance efforts depending on the distance and of course the duration of ride and most importantly where safety of the rider is paramount… but it can be done…
Depending on where and when you ride, a ride to work with some form of efforts and an easy recovery ride home where it generally means the traffic is busier, works perfect giving you some intensity with a recovery balance.
If you then add in a fasted ride in the morning allowing some fat burning with a breakfast once you arrive then you are making the most of your “commuting time” then freeing up that dreaded… I have been at work all day now I need to drag myself onto the trainer conundrum also giving you more time with the family/wife/girlfriend… junk miles… umm really?
This blog comes courtesy of Dr. Haran Sivapalan, Science Writer at FitnessGenes, with input from Ian Jenner, Spokes coach, for the ‘Coaching Perspective’.
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