Cyclical ketosis, glycogen depletion, and nutrient partitioning

Meal & exercise timing in the contexts of “damage control” and nutrient partitioning are frequent topics on this blog.  I generally opt for a pre-workout meal, but nutrient timing hasn’t panned out very well in the literature.  That’s probably why I’m open to the idea of resistance exercise in the fasted state.  A lot of pseudoscientific arguments can be made for both fed and fasted exercise, and since a few blog posts have already been dedicated to the former, this one will focus on the latter.

The pseudoscience explanation is something like this: since fatty acids are elevated when fasting, exercise in this condition will burn more fat; and chronically doing so will increase mitochondria #.  The lack of dietary carbs might enhance exercise-induced glycogen depletion, which itself would bias more post-workout calories toward glycogen synthesis / supercompensation.  Much of this is actually true, but has really only been validated for endurance training (eg, Stannard 2010, Van Proeyen 2011, & Trabelsi 2012; but not here Paoli 2011)… and the few times it’s been studied in the context of resistance exercise, no effect (eg, Moore 2007 & Trabelsi 2013).  However, there are some pretty interesting tidbits (beyond the pseudoscience) which suggest how/why it might work, in the right context.

Exercising fasted or fed for fat loss?  Influence of food intake on RER and EPOC after a bout of endurance training (Paoli et al., 2011)

John Kiefer, an advocate of resistance exercise in the fasted state, mentioned: “the sympathetic nervous system responds quicker to fasted-exercise. You release adrenaline faster. Your body is more sensitive particularly to the fat burning properties of adrenaline and you get bigger rushes of adrenaline.”

Much of this is spot on.  That is, ketogenic dieting and glycogen depletion increase exercise-induced sympathetic activation and fat oxidation (eg, Jansson 1982, Langfort 1996, & Weltan 1998).

The question is: can this improve nutrient partitioning and physical performance?  Magic 8-Ball says: “Signs point to yes.”  I concur.

Contrary to popular beliefs, glycogen depletion per se doesn’t harm many aspects of physical performance.  A lot of fuel systems are at play; you don’t need a full tank of glycogen.

Effect of low-carbohydrate-ketogenic diet on metabolic and hormonal responses to graded exercise in men (Langfort et al., 1996)

High-intensity exercise performance is not impaired by low intramuscular glycogen (Symons & Jacobs, 1989)

Increased fat oxidation compensates for reduced glycogen at lower exercise intensities (eg, Zderic 2004), and ketoadaptation may do the same at higher intensities.

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Ketosis in an evolutionary context

Humans are unique in their remarkable ability to enter ketosis.  They’re also situated near the top of the food chain.  Coincidence?

During starvation, humans rapidly enter ketosis; they do this better than king penguins, and bears don’t do it at all.

Starvation ketosis

 

Starvation ketosis

Humans maintain a high level of functionality during starvation.  We can still hunt & plan; some would even argue it’s a more finely tuned state, cognitively.  And that’s important, because if we became progressively weaker and slower, chances of acquiring food would rapidly decline.

Perhaps this is why fasting bears just sleep most of the time: no ketones = no bueno..?

Observation: chronic ketosis is relatively rare in nature.  Angelo Coppola interpreted that to mean animals may have evolved a protective mechanism against ketosis (if you were following along, please let me know if this is a misrepresentation).

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Circadian phase delays and metabolism

Remember the “jet lag-resistant” mice?  Guess what: screw with circadian biology and metabolism pays the price.

In brief, vasopressin was classically thought of as an anti-hypotensive hormone.  The vasopressin analog Desmopressin is used to treat bed-wetting.  But vasopressin biology is much more interesting than that: mice lacking both vasopressin receptors require very little time adapting to large circadian phase changes.  And as with many fundamental concepts in chronobiology, this is intimately linked with metabolism.

People with certain polymorphisms of the vasopressin receptor, V1A, exhibit elevated blood glucose levels and are at greater risk for diabetes (Enhorning et al., 2009):

genotype

This risk is strongest in men in the highest quartile of fat intake, and is statistically more significant after adjusting for age and physical activity:

Fat consumption

This study wasn’t designed to be a very powerful indicator of diet-disease relationships, but a little speculation: some think higher fat [and lower carb] intake should be protective against diabetes… which may be true, for people who can tell time.  Alter one nucleotide in the vasopressin 1A receptor gene and the game changes.

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Protein “requirements,” carbs, and nutrient partitioning 

One way to determine protein requirements is the nitrogen balance technique.  If all of the nitrogen from dietary protein intake is equivalent to that lost via feces, urine, and sweat, then one is in nitrogen balance.  Growing children and pregnant women are usually in positive nitrogen balance, because much of the nitrogen is being invested in the growth of new tissue.  Cachectic cancer patients and sarcopenic elderly may be in negative nitrogen balance, because they’re losing lean mass.

Protein requirements to maintain nitrogen balance are largely dependent on total energy intake.  More calories in, less protein needed.  For people in negative energy balance (losing weight), this usually means more protein is required else muscle will be wasted.

Exercise lowers, not raises, protein “requirements,” because exercise is a potent anabolic stimulus; it helps preserve nitrogen at any level of dietary protein.  That’s not to say more won’t improve functional outcomes; just that it’s not “necessary” to prevent muscle loss.

Need =/= optimization.

Lastly, total grams, not percent of calories, is the most relevant way to talk about protein requirements in the context of nutrient partitioning and body composition.  This is just how protein operates.

Part 2.  The poor, misunderstood Randle Cycle

“The glucose-sparing effect of fat-derived fuels” …when you’re body starts burning more fat (and fat-derived fuels; ie, ketones), it’s use of glucose declines.  Thus, it’s “glucose-sparing” (spares glucose for the brain and obligatory glycolytic tissues, yada yada yada).

During starvation, much of that glucose comes from amino acids from skeletal muscle proteins, so it can also be phrased as: “the muscle-sparing effect of fat-derived fuels,”  which is equally biologically relevant, because similar to zeroglycemia, an unabated loss of muscle is incompatible with survival.

That is, in starvation, where the “protein” is skeletal muscle, not dietary (because starvation)… but what about when following a low carb or ketogenic diet – do ketones (fat-derived fuels) exert a muscle-sparing effect in this context?

One study compared the impact of two isonitrogenous diets, low carb (Diet A) vs. high carb (Diet B), on nitrogen balance and showed that, except at very high levels of energy intake, nitrogen balance was consistently better on high carb.

carbs vs protein req

 

However, 51 kcal/kg is the textbook number of kcals “required” for young, moderately active adults.  With this understanding, it could be interpreted to mean that nitrogen balance is better with low carb (Diet A) for people in energy balance; and better with high carb (Diet B) if energy deficit.

edit: 51 kcal/kg is for athletes; probably about 20-25% less for non-athletes.

Or not: in another study, a low carb diet promoted better nitrogen retention albeit less weight loss than an isocaloric low fat diet.  The low carb group lost slightly more fat mass, which, combined with nitrogen balance data, suggest modestly improved body composition.  The differences were small, because this was a “non-ad lib” isocaloric diet study.  In the absence of large differences in intake, the most we can expect from such studies are subtle alterations in nutrient partitioning (which are usually difficult to detect).

Cancer cachexia is a condition of severe muscle wasting, and one study set out to determine, more directly, if ketones spared muscle in this context.  The study only lasted one week, but I suspect a certain degree of expedited ketoadaptation because: 1) it was very low in carbohydrate; 2) the fat was primarily MCTs; 3) they supplemented oral ketones; and 4) energy expenditure is elevated in this population.  Both the control and ketogenic diets were modestly hypercaloric, but nitrogen balance was more favorably improved by the high carb diet, in contrast to the above studies.

Thus, ketones don’t work in the context of a hypercaloric diet; however, pharmacologically elevating ketones via intravenous infusion in fasting subjects does work (because it’s more like starvation).

The muscle-sparing effect of fat-derived fuels is conceptually and physiologically more relevant to starvation, not nutritional ketosis.

Part 3.  Protein “requirements”

Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial (Pasiakos et al., 2013) 

Protein intake was 1x, 2x, or 3x the RDA; fat was 30% of calories, and carbs made up the rest; on a weight maintenance diet and again on 30% calorie restriction (it was technically a 40% energy deficit, because they tried to ramp up energy expenditure with exercise).

RDA

All groups lost weight, but the ratio of fat to muscle loss was significantly higher in the 2x and 3x RDA groups, which amounted to ~120 and 185 grams of protein per day, respectively.  The 3x group didn’t fare as well, possibly, because that much protein induces a high degree of satiety – this group ended up consuming significantly fewer calories than the 2x group.  So the interplay between energy intake and protein requirements is back on the table: the added energy deficit apparently increased protein requirements to some level above 185 grams per day.  Not much, given the small difference in muscle loss, but increased none the less.

Side note: be cautious when interpreting a study about the amount of protein required for xyz endpoint, because such studies usually only measure one of many important markers, and they don’t report absolute changes in size, strength, etc.  Also, context matters.

For example, Moore and colleagues (2014) showed that 0.24 g/kg (17 grams for a 70 kg adult) was enough to maximally stimulate myofibrillar fractional synthetic rate (mFSR):

mFSR

However, in the contexts of three square meals and energy balance (or deficit), 0.72 g/kg (50 g/d) is woefully inadequate.  Point being: mFSR (in this case) is only one measurement and shouldn’t be extrapolated to total daily requirements.  Perhaps you could eat six 17 g servings in order to fully maximize 24-hour mFSR, or you could realize that going above what saturates mFSR isn’t a bad thing, or wasteful.  mFSR is just one of many measurements of muscle protein balance.

My opinion

For those who need exact numbers, hopefully one point I’ve made is that there’s no answer to this question.  I’d guess that most people “need” 100+ grams of protein per day (more if losing weight), and 100 grams is probably too much in one sitting.  Also, need =/= optimization, and context matters.

Nutritional ketosis doesn’t appear to reduce the amount of dietary protein necessary to maintain lean mass.  The muscle-sparing of fat-derived fuels works during starvation; in other contexts, all bets are off.

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Carb Back-Loading, take II

I recently had the pleasure of speaking with John Kiefer and his crew about Carb Back-Loading proper; we discussed the protocol and many other hormonal effects associated with this pattern of nutrient & exercise timing.  Interesting stuff; plenty of fodder for future blog posts…

Brief refresher: skeletal muscle insulin sensitivity is higher in the morning than in the evening.  Exercise boosts insulin sensitivity selectively in muscle, which is relatively more important in the evening.  Thus, an evening carb-load may benefit from exercise to effectively partition the energy influx into skeletal muscle [and away from adipose tissue].

Summary of Part 1 of my CBL review: studies on nutrient timing sans exercise aren’t entirely consistent, in part, due to reciprocal regulation of insulin sensitivity in skeletal muscle and adipose tissue.  That is, excess energy from an evening carb-load, without the exercise-induced, skeletal muscle-specific boost in insulin sensitivity, may be biased less toward muscle growth and more toward fat storage, because unlike skeletal muscle, the sensitivity of adipose tissue to insulin appears to improve as the day progresses… and without exercise to offset this, as in the studies discussed below, this may lead to suboptimal results.

*one thing Kiefer stressed, and I agree, is that the effects of any given intervention may be population-specific.  For example, he pointed out that diurnal insulin sensitivity is less robust in obese and aged populations.  So if two findings aren’t in full agreement, click the link to the study and check this first… context matters!

 

 

Tl;dr: I think high intensity exercise and possibly the time of day it’s performed, and regular bouts of fasting, are important factors that mediate the efficacy of CBL and similar protocols. Continue reading

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Carb Back-Loading and the Circadian Regulation of Metabolism

Carb Back-Loading (CBL) redux, part I

Step 1: eat little in the morning (maybe some fat+protein; definitely no carb)
Step 2: exercise in the afternoon/evening
Step 3: eat the carbs, all of them.  Preferably high glycemic carbs.
Other: no dietary fat post-workout; protein periodically throughout the day.

What makes CBL different from its predecessors is the stress on the timing – exercise and carbs in the evening.  John Berardi’s “Massive Eating” dietary guidelines are similar: protein+fat meals all day except pre- and post-workout, which are protein+carb meals.  Martin Berkan’s “LeanGains” is fasting most of the time (including pre-workout), exercise in the afternoon, then a big post-workout meal (quite similar to CBL).  My only tweak, as discussed below (and previously here and here), would be a pre- rather than post-workout meal [in some contexts].

There’s a summary of this blog post at the bottom… it might be helpful to read that first (see: “Tl;dr:”).  Also, please note that much of this post is about the fringe of theoretically optimizing nutrient partitioning, like improving from 85 to 90%, or 40 to 45%, not 40 to 90%…  I’m not that deluded.

My initial take, in general, is that this book is loaded with gems about nutrition, exercise, biochemistry, and physiology.  It’s also very readable and has a lot of good recommendations.  In this post, I want to discuss one specific aspect of CBL: tissue-specific circadian regulation of metabolism.

 

nutrient timing

 

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Paleo Plants and Carnivory

From what I gather, it’s been difficult to pinpoint the role of plants in the diet of our ancestors for a variety of reasons.  For example, evidence of plants on cooking tools and dental remains is suggestive but doesn’t disprove the possibility that said evidence came from preparing the plants for some other purpose (eg, tools, weapons, or medicine), or that the stomach contents of an herbivore was ingested (which gets partial credit).

That said, after reviewing a few studies on the topic (see below), it’s safe to say that plants were eaten, probably frequently, and the types & quantities varied seasonally & geographically.  Collectively, the data suggest we aren’t carnivores.

…you had to have something to hold you over until the next fish fell prey to your deadly hunting spear…  

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Lipid Hypothesis 2.0: Eat Butter

The original lipid hypothesis stated, more or less, that lowering blood cholesterol would reduce premature mortality from heart disease.  At the time, it was thought that dietary cholesterol and saturated fat increased the ‘bad’ type of blood cholesterol, so the advice was to restrict those foods.  All of that was wrong.

Time

Lipid Hypothesis 2.0: Eat Butter

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Fasting, circadian biology, and epigenetics

From the best I can gather, one of the more immediate players in circadian biology is the coenzyme nicotinamide adenine dinucleotide (NAD), which participates in a variety of redox reactions.  Fasting increases the intracellular NAD/NADH ratio, setting off a cascade of events involving epigenetics and the regulation of metabolism.  HT to Jack Kruse for really cracking into this nut.

NAD activates sirtuins, a family of deacetylase enzymes.  This is epigenetics.

SIRT1

 

SIRT1 regulates the activity of BMAL1 and CLOCK, two circadian transcription factors, which target NAMPT, an enzyme that synthesizes NAD.  And in a curious feed-forward mechanism, CLOCK and BMAL1 enhance SIRT1 expression… genetic deletion of any of these players induces insulin resistance (Zhou et al., 2014), and this can be recapitulated with constant darkness: reduced BMAL1 and SIRT1, hepatic insulin resistance; the latter can be reversed with resveratrol (which may or may not be acting through SIRT1; this is controversial).  While alcohol does no great favors for circadian biology, if you’re going to imbibe, perhaps a resveratrol-rich Argentinian malbec served, and this might be the important part, at night, when all of this stuff is going on… coincidentally [fortunately], that’s precisely when most choose to imbibe.

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More on physical performance and ketoadaptation

The various studies on how low carbohydrate diets impact physical performance are very nuanced.  Here’s what I mean by that.

Exhibit A. Phinney 1980

Phinney 1980

In this [pioneering] study, obese patients were subjected to a variety of performance assessments in a baseline period, then after 1 and 6 weeks of weight loss via protein-sparing modified fast (1.2 g/kg ideal body weight from lean meat, fish, or fowl; probably around 80 grams of protein/d, 500-750 kcal/d). They lost a lot of weight, 23 pounds on average, two-thirds of which was body fat. There was no exercise intervention, just the performance assessments.

During the ‘exercise to exhaustion’ treadmill exercise, RQ steadily declined from baseline to week 1 to week 6, indicating progressively more reliance on fat oxidation.  This was confirmed via muscle glycogen levels pre- and post-exercise: during the baseline testing, they declined by 15%; after 6 weeks of ketoadaptation, however, they only declined by 2%, while ‘time to exhaustion’ increased by 55%.  After only 1 week of the diet, time to exhaustion plummeted, as expected, by 20%.

This was, as mentioned above, a pioneering study in the field of ketoadaptation. It also challenges one of the prevailing theories of ‘fatigue’ …while carb-adapted, the subjects fatigued after 168 minutes, with muscle glycogen levels of 1.29 (reduced by 15%); while ketoadapted, they fatigued after 249 minutes with muscle glycogen levels of 1.02 (reduced by 2%).  In other words, they had less glycogen to begin with, used less glycogen during exercise, and performed significantly better (running on fat & ketones).

Exhibit B. Vogt 2003

Highly trained endurance athletes followed a high fat (53% fat, 32% carbs) or high carb (17% fat, 68% carbs) diet for 5 weeks in a randomized crossover study. In contrast to Phinney’s study, these participants were: 1) highly trained; and 2) exercised throughout the study.

Maximal power output and VO2max during a similar ‘time to exhaustion’ test was similar after both diet periods.  Same for total work output during a 20 minute ‘all-out’ cycling time trial and half-marathon running time.  Muscle glycogen was modestly, albeit statistically non-significantly lower after ketoadaption; however, ketoadapted athletes relied on a higher proportion of fat oxidation to fuel performance as indicated by lower RQ at every level of exercise intensity:

Vogt RQ

Again, this is the essence of ketoadaptation. Physical performance as good as or better using fat and fat-derived fuels.

One reason Phinney’s glycogen-depeleted ketoadapted subjects may have done so well is their reliance on ketones (probable) and intramyocellular lipids (IMCL) (possible).  In Vogt’s study, IMCL increased from 0.69 to 1.54% after ketoadaptation…

Also, food intake and body fat declined, and training volume increased in the low fat group; whereas food intake increased, and body fat and training volume declined in the high fat group.  Reminiscent of anything?

High fat, low carb -> eat more, exercise less, STILL LOSE BODY FAT.

Vogt data

Sorcery?  No.  Diet impacts more than just mood and body composition – resting energy expenditure increased in the ketogenic dieters.  This isn’t an isolated finding.

Exhibit C. Fleming 2003 

This was another study in non-trained athletes, consuming high fat (61% fat) or control (25% fat) diets for 6 weeks.  The tests were the 30-second Wingate, to examine supramaximal performance, and a 45-minute timed ride, to examine submaximal performance.

This study differed from the previous two in several significant ways.  For starters, peak power output declined in both groups, slightly more so in the high fat group (-10% vs. -8%).  Furthermore, RQ didn’t wasn’t significantly lower during this test in the high fat group, which possibly suggests they weren’t properly ketoadapted.  In Phinney’s study, the large energy deficit ensured ketoadaptation; this study lacked that aspect, somewhat more similar to Vogt’s, although unlike Vogt’s, these participants weren’t athletes which presumably makes ketoadaptation more difficult.

There are many factors at play… I wasn’t kidding when I said these studies are very nuanced!

Exhibit D. the infamous, Paoli 2012 

These were ‘elite artistic gymnasts,’ who could likely beat you in a race running backwards.  The ketogenic phase consisted of 55% fat and much more protein than the control phase (39% fat; protein: 41% vs. 15%). The significantly higher protein content was modestly offset by slightly more calories in the control phase, which reduces the amount of protein required to maintain nitrogen balance.

In this study, performance was, for the most part, ‘maintained,’ with relative increases in a few of the tests; eg, the “legs closed barrier.”  Changes in body composition were more robust: significantly reduced body fat and increased lean body mass after 30 days of ketogenic dieting (with their normal exercise routine).

Paoli data

The major confounder in this study was the use of an herbal cocktail only in the ketogenic diet group; despite this, the results are largely in line with the other studies.  For more on this study, see here.

Exhibit E. the most dramatic one to date: Sawyer 2013 

Please see here for the details, but in brief, strength-trained athletes showed improvements in high intensity exercise performance after only 7 days of carbohydrate restriction.  The nuances of this particular study are discussed more here.

barbell

Collectively, these studies show that physical performance in both endurance and high intensity realms does not always suffer, can be maintained, and in some cases is improved by ketogenic dieting.  Important factors are duration (to ensure adequate ketoadaptation), energy balance, and regular physical activity (athletes and regular exercisers can adapt to burning fat much quicker than sedentary folks).

 

calories proper

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