|Image 1: The ketogenic diet is also |
referred to as the long chain
triglyceride diet by some dieticians
(image from fingercandymedia.com)
|Illustration 1: Study design.|
... were habituated to a motorised treadmill (Columbus Instruments, OH, USA) over a 14 day period, running at gradually increasing belt velocitiesuntil 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)
[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.
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!