An Objective Review of John Kiefer’s Carb Back-Loading (Part 2)

Continued from part 1


The Limitations of CBL

Some general concerns with CBL

Firstly, I don’t think that eliminating carbs all day is needed for most people, and is potentially detrimental to some, especially those who generally don’t feel good on low carbs, or athletes with high carb requirements. Given the requirement to train in the late afternoon/early evening, CBL is also not practical for those who train in the morning or afternoon. However, Kiefer does address this issue and adapts CBL for people who have work/family commitments that would clash with early evening training. To me, this somehow contradicts all what is said in the rest of the book with regards to physiology and circadian rhythms.

Though I mentioned that knowing you can include some junk food now and again without compromising fat loss is a strength of CBL, encouraging people to splurge on junk food in the evenings – especially when it is stated that goals will be compromised with “healthy” foods (more on that later) – would only serve to encourage unhealthy eating habits. In fairness to Kiefer, he does encourage the consumption of vegetables during the low-carb phase of the day, which if adhered to, would greatly reduce the risk of vitamin and mineral deficiencies.

I also find it ironic that Kiefer writes extensively about the GLUT4 glucose transporter with regards to its ability to shuttle glucose into the muscle cell after training (with the aim of promoting anabolism and muscle glycogen resynthesis), yet advises the consumption of sugar (sucrose) rich foods. As sucrose consists of half glucose and half fructose, the efficiency of muscle glycogen replenishment (and Kiefer’s perceived anabolic response) would be greatly reduced given that fructose is primarily metabolised in the liver. Furthermore, excessive fructose consumption may increase plasma triglycerides (a risk factor for cardiovascular disease).

Additionally, as “no calorie counting [is] necessary” with CBL (although AM protein and fat guidelines are given in the appendices), the vast consumption of “pizza, donuts, pasta, cupcakes, pretzels, popcorn, French fries, ice cream… pecan pie and [Kiefer’s] personal favorite, cherry turnovers” could quite easily result in a massive fat intake predisposing many to fat gain.


Questioning some specific claims of CBL


Right off the bat in the first words of chapter one Kiefer writes:

“Carbs are a drug. As with any drug, knowledge of effects—and side effects—is the only way to guarantee the right outcome. Drugs often hit the market before all the effects show, leaving consumers scrambling for answers, alternatives and adjuncts.”

The comparison he makes between carbohydrates and drugs (and the development of drugs) is completely incorrect and bordering on the ridiculous. The term drug according to Wikipedia can be defined as:

“A substance which may have medicinal, intoxicating, performance enhancing or other effects when taken or put into a human body or the body of another animal and is not considered a food or exclusively a food.”

As carbohydrates ARE considered a food, they don’t fall under the definition of a drug. It therefore appears that Kiefer is willing to sacrifice scientific accuracy in order to get the reader’s attention. Straight away, this tactic puts carbs on a pedestal and heavily implies that knowing how to manipulate carbs - as outlined in the following chapters in the book - will create astounding results; this is simply false.

The book is also scientifically unsound throughout. Furthermore, Kiefer not only cherry-picks data for some of his claims, he also misrepresented some of the research thinks that by dumping 42 pages worth of references nobody would notice. Having checked up on some of the cited references for some of the more questionable claims, many do not support, and some actually contradict Kiefer’s assertions. For example, in chapter 15, Kiefer references the Keim et al. (1997), as discussed in part one, and states that:

“People who eat a big breakfast and start fasting at 7pm lose mostly muscle tissue. People who skip breakfast and eat after 7pm lose body fat and may actually gain muscle. This, dear readers, is fact.”

Notwithstanding the limitations of this study (i.e. the use of BIA and the small sample size of 10 women), the women in the late eating group did not gain muscle (as suggested by Kiefer). In fact, late night eating attenuated losses in LBM relative to consuming the majority of energy earlier in the day. Since this is one of two studies on which CBL is based, the following paragraph highlights why Kiefer may be prepared to bend the truth and state that his assumptions are ‘fact’:

“To maximize the burning of fat and growth of muscle tissue during Carb Back-Loading it seems obvious to eat in sync with how the body also achieves that goal, by having fewer calories in the morning and more at night.”

In order to justify the absence/minimisation of carbs during the day, Kiefer paints a dark picture with regards to insulin and fat gain:

“The earlier carbs slip into the diet, the earlier the body stops burning fat… Limiting carbs, especially in the first half of the day, forces the metabolism to rely on fat for energy needs… Limiting carbs—and therefore limiting insulin release—is crucial for another reason. This is when insulin affects fat cells and muscle cells the strongest, allowing them to store carbohydrates.”

The first statement about carbs increasing insulin release, which causes the body to stop burning fat (lipolysis) is true. However, fat gain can only occur if lipogenesis (fat storage) chronically exceeds lipolysis (e.g. with a 24 hour window). If lipogenesis exceeds lipolysis within a 24h period an individual’s fat balance will be positive (net fat gain). Conversely, if lipolysis exceeds lipogenesis fat balance will be negative (net fat loss). This fat balance is largely determined by total caloric intake, NOT carbohydrate intake. As such, lipogenesis will only exceed lipolysis in the hours after a meal (the postprandial period). The following graph, taken from an article on James Krieger’sWeightology site, demonstrates things nicely.

“After meals, fat is deposited with the help of insulin. However, between meals and during sleep, fat is lost. Fat balance will be zero over a 24-hour period if energy intake matches energy expenditure.”
“After meals, fat is deposited with the help of insulin. However, between meals and during sleep, fat is lost. Fat balance will be zero over a 24-hour period if energy intake matches energy expenditure.”

Regarding Kiefer’s second statement about carbs being stored as fat (AKA de novo lipogenesis: DNL), though the enzymatic pathway for converting dietary carbohydrate to fat exists in humans, DNL rarely occurs in quantitative amounts under most conditions. For example, one scenario in which a significant increase in DNL would occur is during chronic overfeeding of carbohydrates (whereby carb intake exceeds total energy expenditure). By this I mean 700-900g per day for several days, with already full glycogen stores. This doesn’t mean that carbs CAN’T make you fat; they CAN if you eat too many, just predominantly in an indirect manner. In other words, when you eat more carbohydrate, you oxidise more carbohydrate for energy and therefore oxidise less fat. When you eat less carbohydrate, you burn less carbohydrate and more fat. However, if your calorie intake is identical, you also eat more fat so things cancel each other out. Therefore, carbs WILL make you fat if you overeat, but they do so indirectly, by blunting fat oxidation, rather than being directly converted to fat per se. So, after taking protein into account, it would seem to come down to total calories, again.

What’s more, if raising insulin during the day did affect fat loss goals independent of total caloric intake, Kiefer’s recommendations to consume protein (including whey isolates), would compromise these goals due to the insulinogenic effects of protein.

In chapter 17, Kiefer attempts to make a case for evening training based on cortisol response to training (a hormone considered to be catabolic and therefore counterproductive for hypertrophy goals):

“training in the evening causes a lower cortisol response [relative to other times of the day]… This creates an anabolic and anti-catabolic environment greater for evening training than for morning training.”

However, a recent study by West and Phillips (2012), demonstrated that cortisol in response to weight training was positively correlated with gains in LBM over a 12-week period. As it is known that cortisol has the ability to liberate and utilise substrate (e.g. glucogenic amino acids) for fuel, it may be the case that the higher levels of cortisol in those who gained the most LBM was a typical response to simply training harder.

In order to justify his post-training dietary protocols, Kiefer goes as far as to create a straw man, and states that:

“The recommendation is to focus on low-glycemic carbs post-training to stay lean. The argument revolves around having carbs available for hours and avoiding insulin spikes which can make people fat.”

This notion is blatantly false as it is commonplace in gym lore to slam fast-acting carbs post-workout with the aim of spiking insulin.

He further states that:

“After the completion of training, stopping the proteolysis that occurs requires a large insulin spike: the larger, the better. Achieving a big spike takes high-glycemic, high-insulinemic carbs, which we can enhance by adding the right proteins and amino acids.”

Though a rise in insulin is required to inhibit protein breakdown, it needn’t be spiked, especially if the person isn’t training in a fasted state. Indeed, muscle protein breakdown appears to be inhibited with insulin just above fasted levels (15 mU/L), while muscle protein synthesis maximised with insulin 3-4 times fasted levels (15-30 mU/L). Following the consumption of a mixed pre-exercise meal (75g CHO, 37g PRO & 17g FAT), at the one hour mark, insulin is 5x fasting levels, and at the 5h mark, insulin is still elevated enough to minimise protein breakdown. Admittedly, insulin response of such a mixed meal may not be applicable to CBL since carbs are generally reserved for post-workout nutrition. However, Power et al (2009), demonstrated that 45g of a whey protein isolate was enough to elevate insulin enough to minimise protein breakdown for at least two hours, demonstrating the lack of urgency to spike insulin PWO if proper pre-workout nutrition is in place.

It seems as though Kiefer’s recommendations to massively spike insulin rationalise his use of extravagant around-workout supplement concoctions, highlighted in the figure below.

Screen Shot 2013-05-03 at 15.03.40
Screen Shot 2013-05-03 at 15.03.40

Though I could spend an entire article in itself detailing why these protocols are unnecessary, the crux of my issue is that having three different types of protein as well as added leucine, all in the same meal, is utterly ridiculous. If you recall from my article series on BCAAs, a whole protein containing 3-4g of leucine is enough to maximally stimulate muscle protein synthesis and inhibit muscle protein breakdown. As such, consuming sufficient amounts of a whey isolate (roughly 25-35g) would provide the same benefit but without the added hassle/expense, not to mention the horrid taste because of the free-form amino acids. Add a creatine monohydrate supplement on top of that (and perhaps some caffeine if you feel you need it) and you’re good to go.

Going back to Kiefer’s point about avoiding low glycaemic index (GI) carbs post-workout, he further states that:

“The few health and diet gurus who’ve jumped on the back-loading bandwagon suggest evening options based on pop-diet culture, e.g. low-glycemic carbs. Not only is this advice wrong, but fat-inducing… You need to eat very high-glycemic carbs for Carb Back-Loading to work… The body releases growth hormone at night, but it won’t begin doing so until insulin levels return to normal and stay at that level for about two hours. Eating the high-glycemic goodies causes a big rush of blood sugar and jolt of insulin, then a quick drop as things settle back to normal, leaving the nocturnal hours free of insulin and full of growth hormone.”

This reasoning is incorrect on several levels. Firstly, growth hormone is not anabolic within physiologic ranges (and perhaps even with supra-physiologic doses). In addition, it appears that growth hormone release occurs at the onset of sleep independent of the blood glucose and insulin levels that occur in response to a meal consumed in the hours prior to sleep. Furthermore, if someone trains at around 5pm, as Kiefer suggests, they would be consuming their post-training shake at roughly 6:30pm and start eating dinner at around 8-8:30pm. Assuming somebody would want to get to sleep by 11pm, this would allow a 2.5-3 hour window for insulin to return to basal levels. However, Tipton et al (2001) observed that only 6g of essential amino acids plus 35g of sucrose was enough to keep insulin elevated above basal levels for almost three hours. As such, it would be reasonable to suggest that a much larger meal, as recommended by Kiefer, would keep insulin elevated for much longer that three hours, regardless of GI of the carbs contained within the meal. Here’s the kicker, Kiefer in fact recommends consuming highly insulinogenic protein sources (e.g. eggs, milk and whey isolate) prior to bed, and according to his logic, would be shooting himself in the foot by doing so.

There are literally dozens more examples that I could’ve chosen from, but I aim to keep this review to a reasonable/readable length (to my standards, at least). To give you a taster, these include things such as:

  • Inventing cool-sounding phrases such as Modulated Tissue Response (MTR), which involves “the ability to select which tissues grow and which shrink”.
  • Vastly oversimplifying some physiological processes to the point of being incorrect (e.g. “Testosterone is anabolic for muscle tissue; estrogen is anabolic for fat tissue”).
  • In chapter 35, he states that whey isolate doesn’t interfere with fat burning (implying that it doesn’t affect levels of insulin or free fatty acids), but provides a reference demonstrating that the opposite is true.
  • In chapter 41 (I couldn’t believe my eyes when I read this), “The worst, in almost all protocols, is the supplementation requirements.” To be fair to Kiefer, I have seen much worse.
  • His recommendation to train fasted in chapter 43, in order to increase fat oxidation during exercise, doesn’t seem to make a difference in terms of 24 hour fat balance.
  • Finally, in chapter 50, Kiefer writes, “I don’t recommend cardio, at least not long duration, steady- state cardio. I don’t care about the goal: this type of cardio is essentially useless, even for marathon training.Researchand the experience of many of the best coaches in the world would disagree.

Summary and Practical Recommendations

The general concept of CBL is supported by science. However, this science is limited to two studies with their fair share of limitations, rendering the topic inconclusive in the absence of compelling evidence. Moreover, if we consider shifting only carbohydrate as opposed to overall caloric intake, the data supporting the concept of CBL diminished to a single study. Nevertheless, if we consider the overall impact of calorie/carbohydrate placement on body composition from these two studies, though significant, in reality such differences are trivial.

Though CBL has some positive aspects to take away, as well as being generally supported by science and solidly referenced throughout, for me, it contains few too many incorrect and bold claims, which seem to rationalise specific recommendations (e.g. the elaborate supplement protocols).

Because of the rigidity of CBL with respect to its training and dietary recommendations, adherence may become an issue for all but the most dedicated dieters/trainees. After all, adherence to a specific protocol is the single most important determinant of long-term success.

In my opinion, the total macronutrients consumed by the end of the day will have the largest impact in terms of body composition changes; Kiefer even admits this (at least in regards to meal frequency), “the breakdown and distribution of calories and macro nutrients throughout the day matters far more than the number of meals”. At the end of the day, CBL will get some people results, but it will do so because of the caloric deficit and sufficient protein, not because of the intricate protocols.

As such, with respect to carb placement for body composition and performance, total intake is the primary consideration. A secondary consideration would be the positioning of these carbs in relation to training (around-workout nutrition) in order to optimise training performance. Once these factors are in place and consistently achieved, then, and only then, should someone have the option to experiment with hypothetical protocols.