Discussion in the nutrition community has been flourishing around the concept of high-fat diets lately, and the concept of metabolic flexibility seems to have some logic behind it, which is why the professional cycling world has been paying attention.
Why would the cyclist bother though? Can’t we just lose fat by eating less on a regular diet? Why the need for another dietary gimmick? In fact, why lose fat at all?
The concept goes something like this: by intermittently restricting your body of carbohydrates, you’re forced to develop your ability to turn fats into energy, therefore becoming more efficient at doing so.
To simplify, this idea of ‘metabolic flexibility’ is adding flexibility to your body’s metabolism, thus increasing the body’s ability to derive energy from fats.
There are a couple of reasons such a movement might have merit in the cycling world. Not only does the human body generally have vast stores of fat to access as energy, both reducing body-fat and increasing power-to-weight, but fat has shown to be a ‘cleaner’ energy, producing less inflammation at the cellular level than energy from carbohydrate.
This latter point is contested, as well as being potentially irrelevant due to the fact that no research has yet shown that the human body can source energy from fat at extremely high heart-rates. Regardless though, the ability to derive energy from fat and reserve our carbohydrate stores for moments in need remains a huge potential benefit.
Research has shown that certain dietary fats are more easily converted into energy than others. Since the concept of all saturated fats being unhealthy has been debunked, analysis of what each branch of saturated fats does has surfaced.
Medium chain triglycerides, the types of ‘saturated’ fat abundant in grass-fed cows’ butter or young coconut oil, for example, have been shown as highly beneficial to the body, as well as being easily transferable into ‘ketonic’ energy.
Fat compositions therefore become very important for the cyclist wanting to improve their metabolic flexibility.
One example being grain-fed/barn-raised cattle versus cattle that walked around in pastures eating grass before their sacrifice. Comparing the fat compositions shows much less beneficial fats (omega 3, ALA) and more inflammatory trans-fats and omega 6 in the grain-fed/barn-raised animal produce.
This application is relevant for both the dairy and meat, and I suggest researching further how much benefit can be derived from quality meat and dairy, if cellular inflammation and metabolic flexibility are topics of your interest.
So what’s the catch? Well it’s a big one. As mentioned above, no research is yet to suggest that completely carbohydrate-free energy production is plausible for high heart-rate exercise. Conventionally, fat is still understood to provide a slower energy supply than that of carbohydrate at high heart-rates that require highly-responsive energy production, but it is up for debate whether or not this can change as the metabolism evolves.
Garmin-Sharp and Belkin are two professional cycling teams that have suggested carbohydrate-fasting (and thus fat metabolism) of their riders for many years now. Metabolic flexibility has become a seemingly amicable physiological trait for endurance performance, and professional cyclists have forever (unconsciously) aligned with the concept by fasting on long, slow training rides.
Cycling for the most part lies in the intersection – the proverbial grey zone – of energy systems. Unlike other endurance sports, a racing cyclist spends large amounts of time at lower heart-rate zones, before explosions at the extreme high end. Their are obvious exceptions, depending on course, rider, and whether the race is a multi-stage tour or a one-day event.
Mountain stage intensities vary depending on riders, but the average heart-rate zone would be aerobic threshold (AT) or higher for the climbs, and less than 50 per cent while descending (with exceptions).
Breakaways, on the contrary, tend to place a rider at or just below their AT for many hours at a time. This scenario wouldn’t allow for any fat-derived energy unless the cyclist had trained their body to be capable of processing fat into energy at AT heart-rates, which hasn’t yet been documented as possible.
Considering this, cycling is unlike the comparable ultra-marathons of running, for example, which are generally competed at below AT, but for much longer periods of time. Instead, the cyclist’s physiology must be prepared for shorter stints below AT intensity as well as random bouts above.
So what about becoming lean? This year Vicenzo Nibali’s Astana team publicly attacked his flabby belly before the Tour de France that he dominated. He was heckled as being fat in the Criterium du Dauphine weeks before the Tour, and once leaning up pre-Tour he was quoted as having said he simply stopped eating desserts and reduced his pasta quota.
This to me, seems a hilariously simple response, quintessential of Italy’s fortified food traditions. How he actually reduced his calorie intake while completing his hardest training of the year baffles me. Two possible answers are he either replaced such calories with fats, proteins, or wine, or perhaps he is a liar.
I don’t care, I just think the general traditionalist mentality of burning fat is flawed within the cycling world.
To burn fat, many mainstream coaches will advocate occasional days of staying in ‘the fat burning zone’ to ‘lean up’. This is the heart-rate zone where your body derives the highest proportion of its energy from fat. The catch is you’re still actually burning more fat at heart-rates above this glorified zone, it’s just the ratio of the sourced energy is leaning in favour of carbohydrates.
On top of this, the muscle damage and fatigue the body endures from higher heart-rates correlates to higher fat-burning as a part of the recovery process (through required energy consumption). It’s also important to remember that cholesterols exist in all cells, so the right fats (like the examples mentioned above) too play a part in muscle recovery.
So what’s the take-home message? Metabolic flexibility. The potential to allow the cyclist to improve their body’s efficiency at burning fat, and burn more fat at higher heart-rates.
As the cyclist trains their body via intermittent carbohydrate starvation to derive more energy from fats, this metabolic training takes place. The cyclist will therefore not only lean-up but theoretically rely less on the body’s glycogen stores at lower heart-rates, saving the precious calories for moments deep in the ‘hurt station’.
As Ernest Shackleton lived on mostly seal blubber for months on end, it appears we might just be able to follow in his foot steps (without the constipation) if we keep our heart-rates below paramount.
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