Long Chain Triglyceride Feeding Reduces Exercise Performance by >55% - Cambridge Scientists Find Reduced Mitochondrial Efficiacy in Rat Hearts.

Image 1: The ketogenic diet is also
referred to as the long chain
triglyceride diet by some dieticians
(image from fingercandymedia.com)

In view of the current low-carb hype, people tend to forget that, after all, carbohydrate consumption has been shown time and again to improve the performance of endurance athletes. And despite the existence of a few studies about "fat adaption" which report equal or even improved endurance performance in athletes on low carb diets, previous findings of Murray and his colleagues from the Department of Physiology, at the University of Cambridge clearly showed detrimental effects of short term high fat feeding (9 days) on the exercise capacity of rats. These results are corroborated by findings of Holloway et al. (Holloway. 2011) who found cardiac high-energy phosphate metabolism and cognitive function to be impaired in healthy human subjects on a high-fat diet. Now, it is quite obvious that these findings stand in contrast to all the beneficial effects about which you have read at the SuppVersity and even much more mainstream scientific webpages, such as Science-Daily, lately. Well, I guess this makes the results of Murray et al.'s latest study particularly interesting (Murray. 2011b).

Illustration 1: Study design.

In order to find out what the differential effects of medium and long chain triglyceride feeding on rats were the scientists allocated 33 rats to one out of six groups (cf. illustration 1), of which three were allowed to live a lazy rat-life, while the other three groups (the exercise groups)

... were habituated to a motorised treadmill (Columbus Instruments, OH, USA) over a 14 day period, running at gradually increasing belt velocities

until the rats were "proficient at running on the treadmill for 5 min at a velocity of 10 m/min on a 5° incline". And while I do not think you would call running on a 5° incline at a speed of 10m/min (=0.6km/h or 0.37miles/h) exactly "athletic" in human terms, this was only the initial speed the treadmill was set to in the exercise tests in the course of which the speed was increased by an additional 1 m/min with each minute until the rat fatigued.

Other than one may have expected, none of the fat-feedings induced significant changes in body weight in the sedentary rats, when compared to their chow fat controls (cf. figure 1). The +59% increase in visceral (epididymal) fat, the LCT fed rats experienced, is however a clear marker of impeding metabolic derangement and indicates, in the presence of otherwise unchanged bodyweight, a significant loss of lean body mass in the long chain triglyceride fed rats.

Figure 1: Selected biomarkers of sedentary and exercised rats after 15 days of standard chow, high medium chain triglyceride or high long chain triglyceride diet in comparison to chow fat, non-exercised control
(data calculated based on Murray. 2011b)

In the exercised rats, on the other hand, medium chain triglyceride feeding had quite similar effects (+44% vs. sedentary chow fat control), although the shorter MCTs did not exert any significant detrimental effect on the exercise capacity of the rats.

Image 2: Current research
suggests that MCT oils are
probably not useful to athletes
who are not on a very low
carbohydrate diet. The replacement
of long chain with these shorter
chain triglycerides, on the other
hand, could make sense from a
performance point of view

Medium Chain Triglycerides, the performance fats? While there was no decrease in performance observed in the MCT group in the study at hand, the performance increase some supplement companies will promise in order to sell their MCT oils and/or MCT-enriched supplements, was non-existent as well. In this regard, Murray et al. remark that

[i]t has been theorised that MCT-rich diets might improve energy utilisation during exercise, perhaps through increased ketogenesis, however there is little conclusive evidence for this.

Interestingly, one study that is often cited in this context (Fushiki. 1996) in which the swimming endurance capacity of mice fed an MCT-rich diet over 6 weeks increased, used a LCT-fed mice as controls. In view of the results of the study at hand, this "ergogenic effect" of MCTs has to be reevaluated. It is in fact much more likely that MCT-fed rats just avoided the detrimental effect of the LCT diet.

So what does all that go to say for you, as an active or even athletic human being who is trying to find the appropriate and delicate balance between health, looks and performance? A fundamentally important observation was made in this context by the same group of Cambridge scientists a few month before (Murray. 2011a), when they found that endurance exercise training blunts the deleterious effect of high-fat feeding on whole-body energy efficiency and mitochondrial respiration - much to the scientists surprise highly trained endurance athletes appeared to even thrive on the "bad" high fat diet.This is an observation I would attribute to what I initially referred to as "fat adaption", i.e. an improvement in both rate and energy efficacy of fatty acid oxidation in a group of people whose bodies are used to literally "run out of carbs", no matter how many energy gels they are consuming in the course of a competition.

With regard to the fatty acid specific differences Murray et al. observed, one could speculate that in an intermediate phase, i.e. for example in the first 2 weeks of low-carb dieting, where most dieters complain about low energy levels, brain fog and other symptoms of suboptimal energy metabolism, the use of MCTs to provide "carb-like instant energy" could provide an adequate strategy to bridge the time-gap your body needs to ramp up mitochondrial fatty acid oxidation in order to fuel your metabolic demands from dietary fats, alone.

If you have read the Amino Acids for Super Humans write-up on l-carnitine, you are probably already aware that supplementation with L-3-hydroxy-4-N,N,N-trimethylaminobutyric acid (l-carnitine) could help to speed up / sustain your ability to use (long chain) triglycerides as fuel by shuttling the fatty acids into and (this is commonly overlooked) out of your cellular power plants (if you want to know more about LCAR, ALCAR, LCLT & co, read Part IV of the Amino Acids for Super Humans Series).

That being said, it would be interesting to see a similar LCT feeding study with appropriate adaptation times in order to decide whether the rats just were not accustomed or generally unable to efficiently metabolize the long chain triglycerides and to access what the long-term consequences of the upregulation of PPAR-gamma and UCP3 in the heart muscle will look like. I'll keep you updated!