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Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n = 10, %carbohydrate:protein:fat = 59:14:25) diet, and the other a low-carbohydrate (LC; n = 10, 10:19:70) diet for an average of 20 months (range 9 to 36 months).
I just discovered your site and have been thoroughly enjoying many of the articles and appreciate that you get so in depth in your explanations. I’m in my late 40’s and, while not an extreme endurance athlete, I am moderately active with 18-20 mile rides 3x a week as well as some boxing and body weight resistance (push up, pull up, etc) mixed in. I’ve generally been paleo and stick to quality macros for the most part (grass fed meats/dairy, organic veg and oils) and zero supplements. I recently started following keto (after reading this article) about 10 days ago and things seem good thus far. I do, however, want to avoid any of the negative side effects you mention and also not lose any lean muscle. I’m currently about 174 lbs, 5’8″ and about 19% bodyfat – I’m taking in about 95g protein, 130g fat and <20g net carbs. I'm eating all quality – wild salmon, grass fed beef, pastured eggs, coconut oil, Brain Octane and Grass fed butter in coffee, sardines, etc. With a smattering of organic veg, but it seems real easy to bust through the carb barrier. *I'M ALSO TAKING KETOCANA PRE-WORKOUT* and I notice this is keeping me going throughout a ride or the gym.
And it all culminated with me stepping into Dr. Jeff Volek’s world famous laboratory at University of Connecitut to subject myself to extensive blood testing, chunks of muscle removed from my legs, fat sucked out of my butt-cheeks, urine, stool and gut microbiome testing, oxygen and carbon dioxide testing and countless hours of treadmill running to discover what a full twelve months of eating a ketotic diet had actually done to my body.
I talk about that quite a bit here :https://bengreenfieldfitness.com/2015/09/things-your-pee-can-tell-you-about-your-body/
One more thing that I noticed is that my HR does not move Beyond a certain point. I can still perform quite at a high level and faster than most people at my box but weirdly enough it’s like there’s a block on my HR which doesn’t allow it to move beyond 160 bpm. I’m not sure if this is good or bad! Could I go even faster if my HR would pass this limit?? It is a physiological barrier created by the glycogen sparing mechanism that doesn’t allow my body to move after a certain point so it won’t have to tap into my glycogen stores or force my body to go into gluconeogenesis?? If I added some more carbs around my workouts would it be easier to get the glycolytic pathway to work more effectively since it’d be faster and easier fuel? I read about the downregulation of PDH enzymes after prolonged keto and I constantly worry that I dont use my glycolytic pathway as effective anymore. I LOVE this lifestyle but at the same time, as athletes; we’re always thinking on how to improve performance. What are your thoughts?! Thank you so much!!

The second type of cellular fuel comes from fat and fat metabolism products called ketone bodies.   The average sized human body can store hundreds of thousands of calories in the form of fat, so we could say that this system of energy is almost unlimited, depending on how long one goes without food.  Eventually, it would get used up, but people have been known to fast for months and live through it.
After 2 years in ketosis suddenly I find my blood glucose has risen to high levels even while in ketosis. I thought it was the dawn phenomenon, stress hormones like cortisol but now I am beginning to think I am eating too many exongenous keytones like too much MCT oil? I am not taking exogenous keytone supplements but wondering if too much oil/ fat in the diet generates exogenous keytones which inhibits the livers production of endogenous keytones. I have read if the liver is producing endogenous keytones it is not at the same time producing glucose through gluconeogenisis?
An interview with University of Florida researcher and scientist Dominic D’ Agostino. In that episode, “A Deep Dive Into Ketosis: How Navy Seals, Extreme Athletes & Busy Executives Can Enhance Physical and Mental Performance With The Secret Weapon of Ketone Fuel“, Dominic highlights his research into the use of ketones to enhance breathhold time and reduce the brain’s requirements for oxygen.
Would be curious to receive feedback on any of the above! And if anyone is interested in more info on my future Ketone product which will taste great, have 11.7g of BHB, 30 servings and priced lower than all the competitors, then message me on FB under Rhys Kabra, or email [email protected] for status updates on the upcoming new Brand of Ketone products! :)
“To achieve the relatively high rates of intake (up to 90 grams/hour) needed to optimize results in events lasting longer than three hours, athletes should practice consuming carbohydrates during training to develop an individual strategy, and should make use of sport foods and drinks containing carbohydrate combinations that will maximize absorption from the gut and minimize gastrointestinal disturbances.”
For any long 90+ minute workouts or competitions for which glycogen depletion is a potential issue, use Glycofuse, but use half of the recommended serving of it, and add one scoop of Catalyte electrolytes, one scoop of Aminos, and one serving of medium chain triglycerides in the form of Brain Octane, KetoCaNa or KETO//OS (pick your poison, it’s up to you).

I would do breath ketone measurements. That's exactly what I do and this is what I use
:https://greenfieldfitnesssystems.com/product/ketonix-breath-ketone-monitor/
While it is believed that carbohydrate intake after exercise is the most effective way of replacing depleted glycogen stores,[72][73] studies have shown that, after a period of 2–4 weeks of adaptation, physical endurance (as opposed to physical intensity) is unaffected by ketosis, as long as the diet contains high amounts of fat, relative to carbohydrates.[74] Some clinicians refer to this period of keto-adaptation as the "Schwatka imperative" after Frederick Schwatka, the explorer who first identified the transition period from glucose-adaptation to keto-adaptation.[75]

Being in optimal ketosis for a prolonged period of time (say, a month) will ensure that you experience the maximal hormonal effect from eating a low-carb diet. If this doesn’t result in noticeable weight loss, you can be certain that too many carbs are NOT part of your weight issue and not the obstacle to your weight loss. There are, in fact, other causes of obesity and being overweight. The next three tips in this series might help you.
Insulin is a hormone that lets your body use or store sugar as fuel. Ketogenic diets make you burn through this fuel quickly, so you don’t need to store it. This means your body needs -- and makes -- less insulin. Those lower levels may help protect you against some kinds of cancer or even slow the growth of cancer cells. More research is needed on this, though.

A study in the Journal of Applied Physiology showed that people who do twice-a-day workouts, but defy standard nutrition recommendations by not eating for two hours after the first session (thus depleting carbohydrate stores with the first session) experienced a better ability to burn fat (with no loss in performance) compared with a group that trained only once a day and ate carbohydrates afterward.
Jalali says people following the diet have the best chance of keeping the weight off if they stay on it long term. And that’s not always easy to accomplish. The weight may come back if you go back to your regular eating habits. And regaining weight may lead to other negative effects. “Chronic yo-yo dieting appears to increase abdominal fat accumulation and diabetes risk,” notes Clark.
For any long 90+ minute workouts or competitions for which glycogen depletion is a potential issue, use Glycofuse, but use half of the recommended serving of it, and add one scoop of Catalyte electrolytes, one scoop of Aminos, and one serving of medium chain triglycerides in the form of Brain Octane, KetoCaNa or KETO//OS (pick your poison, it’s up to you).
The presence of abnormally high levels of KETONES in the blood. These are produced when fats are used as fuel in the absence of carbohydrate or available protein as in DIABETES or starvation. Ketosis is dangerous because high levels make the blood abnormally acid and there is loss of water, sodium and potassium and a major biochemical upset with nausea, vomiting, abdominal pain, confusion, and, if the condition is not rapidly treated, coma and death. Mild ketosis also occurs in cases of excessive morning sickness in pregnancy.
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