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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New study: high intensity exercise on a low carb diet.

Switch an athlete from their standard carbohydrate-rich diet to a low carb ketogenic one and suddenly performance tanks.  It is known.  Give them a few weeks to adapt, however, and it recovers.  This much was established for mainly endurance-related performance parameters by Steve Phinney and colleagues in the 1980’s (eg, Phinney et al., 1983).  Then, along came Antonio Paoli, Dominic D’Agostino, and others who showed a similar phenomenon in gymnasts, a population that routinely exercises at higher levels of intensity (Paoli et al., 2012).  Notably, in these studies the athletes were allowed adequate time to adapt to the new metabolic milieu – sometimes referred to as ketoadaptation.  Three weeks appears to be the minimum amount of time required for ketoadaptation; ie, studies of shorter duration generally show: low carb = poor physical performance.

…which is why I was surprised to see this one:

Effects of a short-term carbohydrate-restricted diet on strength and power performance (Sawyer et al., 2014)

These researchers subjected ~30 strength-trained individuals to a battery of performance assessments before and after 7 days of a low carb [ketogenic] diet.  Usually I would’ve stopped reading at this point because 7 days is too short.  But there were some nuances in the way this particular study was designed which piqued my interest.

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Advanced glycation end products (AGEs)

About a decade ago, Michael Brownlee posited that AGEs were one of The Four Horsemen responsible for the microvascular complications of diabetes.

Kill ‘em all

Thereafter, the image below (or a closely related one) appeared in at least one talk at every major diabetes conference for about 5 years.  Then it faded – maybe not because it is wrong, but rather just too simplistic to be useful (similar to CICO & ELMM).

Brownlee

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Skipping meals, intermittent fasting, grazing, etc.

or… Circadian Meal Timing!

They say if you’re going to [intentionally] skip a meal, it should be breakfast – and hey, that’s probably the easiest meal to skip.  However, a recent study showed skipping dinner FTW (well, not exactly).  I’ve never seen a proper study directly comparing the effects of skipping different meals, but here are a few that come close.  The findings may surprise you.

omelette

note: with the exception of Fernemark (Exhibit B), these studies are mostly macronutrient-controlled. That is, protein, fat, and carbs are similar between the groups; the only thing that differs is when they were ingested.  This can be tricky and/or very nuanced in some instances, like if dinner was smaller (fewer calories) but more protein-rich, for example… but in order to include 5 relevant studies and not bore you to death, you’ll have to check the full texts for those details.

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Nutrient Partitioning: …a *very* high protein diet.

Or: what happens when you eat a ton of protein?

RDA: 0.8 g/kg

Active individuals: 1.2-2.0 g/kg (via ISSN)
Comment (1): I think sedentary, physically inactive, and non-exercisers should be in this range to offset disuse atrophy.  And they should exercise.
Comment (2): Do athletes really need more protein than non-athletes?  They have exercise, a powerful anabolic stimulus.  More protein may improve performance or body composition, but they might not *need* it, in terms of nitrogen retention… there’s probably a study on this.

NEED =/= OPTIMIZATION

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