Putting Carbs to Good Use: Meta-Review Reports Ergogenic Effect of Carbohydrates in Endurance Athletes

One of the leitmotifs, many of my posts here at the SuppVersity share, is the idea that (almost) everything works for someone. From the feedback I am receiving, from the crowd this blog is attracting, I gather that my general advice against high carbohydrate intake is (as human as that may be) often misinterpreted as "carbs are evil, beware of all carbs"! For the average pizza eating fast-food junkie, this certainly is an adequate message, because even if he believes that carbs are the root of all disease, without a MAJOR change in his dietary habits (I am not talking of ordering the normal, instead of the super size menu at McDonalds, here) he will probably still get way more carbs out of his diet than it would fit his sedentary lifestyle.
If, however you are an athlete or avid gym-goer you may probably already start to notice that following what you took to be a one-solution-fits-it-all recommendation lead to performance decreases, laziness, brainfog, lack of sexual desire, bad sleep and many of the other symptoms you would find, when you googled one of the ambiguous terms "adrenal fatigue" or "general fatigue syndrome"... Carbs are more than just insulin triggers, and fatteners. Glucose is the gasoline in your fuel tank and - most importantly - its the substrate your nervous system thrives on. And while it might not be necessary to eat them, very active (and lean) individuals may derive similar benefits from a moderate carb consumption as the athletes from the 50 studies included in a meta-review by Themesi et al. (Themesi. 2011).

The scientists' results suggest that intake of a <8% carbohydrate beverage (~50-80g) [TT] in the course of an endurance event (≥1 h) significantly "enhances endurance exercise performance in adults" as measured by submaximal exercise performance and time to exhaustion [TTE]:

The ES [effect size] for submaximal exercise followed by TT was significant (ES = 0.53; 95% CI = 0.37–0.69; P < 0.001) as was the ES for TT (ES = 0.30; 95% CI = 0.07–0.53; P = 0.011). The weighted mean improvement in exercise performance favored CHO ingestion (7.5 and 2.0%, respectively). TTE (ES = 0.47; 95% CI = 0.32–0.62; P < 0.001) and submaximal exercise followed by TTE (ES = 0.44; 95% CI = 0.08–0.80; P = 0.017) also showed significant effects, with weighted mean improvements of 15.1 and 54.2%, respectively, with CHO ingestion. Similar trends were evident for subanalyses of studies using only male or trained participants, for exercise of 1–3 h duration, and where CHO and PLA beverages were matched for electrolyte content.

Against this background, can the relevant question really be: "To carb or not to carb?" Probably not. You better follow Vince Andrich's recent advice and ask yourself "Are you working your sugar-bags (muscles) hard enough to earn your fair share of carb intake?" in order to make sure that you use just as much carbs as it takes to optimize performance without compromising health and body composition.

Effects of Macronutrient Composition on Metabolic Signaling: Higher Protein Diet Favors Glycogen Storage in Muscle Over Adipose Tissue

Those of you who have already listened to the latest, revamped (and improved) episode of Dr Scott Connelly's BodyRx Show will already have heard of Suzanne Devkota's and Donald K Layman's study (Devkota. 2011) on the effects of different meal compositions on the postprandial glucose disposal. For the rest of you who have missed the episode and those of you who like their info white-on-black, here are the main results...

For 10 days, Devkota and Layman fed 60 rats a diet containing either 60% of energy from carbohydrates, 12% protein, 28% fat (CHO) or 35% carbohydrate, 35% protein, 30% fat (PRO) and evaluated plasma levels of insulin, glucose and C-peptide, as well as muscle and adipose tissue Akt, p70S6K and Erk 1/2 (markers of glucose and protein metabolism and cellular growth, respectively).

The graphs in figure 1 illustrate their most significant finding quite nicely. Other than in the case of the protein-fed rats, blood glucose is preferentially stored in fat tissue in the 30-90 min time window upon the ingestion of a meal in the high carb (CHO) group

Figure 1: Muscle and adipose tissue Akt expression (marker of glucose metabolism) after "high" protein (PRO) and high carbohydrate (CHO) meal, respectively (Devkota. 2011

The authors summarize this effect of macronutrient partitioning on metabolic signaling that is supported by the rest of their data as follows:

Animals chronically consuming the CHO diet produced greater metabolic signaling in adipose tissue to handle excess glucose and blunted signaling in skeletal muscle consistent with interpretation of insulin resistance. Conversely, animals consuming the PRO diet produced greater metabolic signaling in skeletal muscle with little signaling in adipose.

To fuel your workouts, it thus seems not only unnecessary, but even detrimental, to consume high amounts of carbohydrates. A "lower"  [note: even the high protein diet that was matched to the USDA's acceptable macronutrient distribution ranges (AMDR) had a carbohydrate content of 35% and thus a 1:1 protein to carb ratio!] carbohydrate intake, on the other hand, appears to prime your body to store glycogen primarily in muscle tissue. On a "high" protein, "lower" carb diet, you thus get the performance benefit without the unwanted fat gain and isn't this what we all are looking for?

Protein's Effects on Gene Expression: Higher Protein Lower Carbohydrate Diet Spares Gylcogen, Lowers Insulin and Reduces Lipogenesis

High protein diets have become the "gold standard" within the fitness community. On the countless bodybuilding, fitness and weight loss related bulletin boards on the Internet, athletes, gymrats and even overweight house-wives report outstanding benefits of a higher than normal protein intake on weight gain and/or fat loss. French scientists (Stepien. 2011) have now taken a closer look at the mechanism behind these success stories and found a strong (epi)genetic component (for an introduction to epigenetics, I recommend listening to Dr Rouse's interview series on Carl Lenore's Super Human Radio).

 Figure 1: Effect of high protein diet on genes regulating lipogenesis [lipo = fat; genesis = production] in the liver (Stepien. 2011)

Stepien et al. fed 80 male winstar rats either a normal or a high protein (50% protein) diet for 1,3,6 or 14 days and evaluated the mRNA levels [indicators of how active these genes are] of genes "involved in carbohydrate and lipid metabolism", energy expenditure (EE) and substrate oxidation, as well as liver glycogen, plasma glucose and hormones. What they observed stands in line with the positive anecdotal evidence you will find if you google muscle gain or fat loss "success stories":

    In liver, HP feeding 1) decreased mRNA encoding glycolysis enzymes (GK, L-PK) and lipogenesis enzymes(ACC, FAS), 2) increased mRNA encoding gluconeogenesis enzymes (PEPCK), 3) first lowered, then restored mRNA encoding glycogen synthesis enzyme (GS), 4) did not change mRNA encoding b-oxidation enzymes (CPT1, ACOX1, bHAD).

So, interestingly, with the exception of the 1st day of the experiment (where the increase in protein intake resulted in a short-term increase in fat oxidation), fat oxidation was stable (cf. 4) The "fat burning" effect, which is often ascribed to high protein diets, thus is not existent - or let's say its not a direct one, but a result of the synergy of other genetic and metabolic adaptations and the calorie restriction all weight loss regimens have in common.

Figure 2: Postprandial macronutrient balance as assessed during a 4 h period after the intake of a calibrated meal consisting of 4 g of an adequate diet.  (Stepien. 2011)

Here is where the insulin lowering effect, the reduced hepatic glucose uptake and the reduction in lipogenesis (cf. fig. 1) come into play. Combined with an overall increase in postprandial energy expenditure (observed only under long term high protein feeding conditions, cf. fig 2, HP14) and a slight but significant increase in the percentage of fat (LOX, fig. 2) that is used to fuel these demands, these genetic and metabolic adaption (most prominently the lower insulin levels and the reduction in lipogenesis) are the most probable mechanisms to explain the reduced fat gains and increases in fat loss on high protein weight gain and weight loss diets, respectively.

Carbohydrate Restriction Reduces Liver Triglycerides More Effectively Than Calorie Restriction - With Equal Weight Loss Outcomes.

A calorie is not a calorie, I hope you knew that even before Garry Taubes published his famous NY Times best-seller. Yet, in case you are still looking for respective studies to show to medially indoctrinated family members or friends, who still believe that - even if fat is not the enemy - half ratios would be the key to health & longevity, you might be interested in the results of a very recent investigation by Browning et al. (Browning. 2011).

The scientists put a group 18 non-alcoholic-fatty-liver patients on either a carbohydrate-restricted (<20g/day) or a calorie restricted (1200-1500kcal/day) diet - just to make sure you get this right: the carb-restricted group ate as much calories as they wanted! - and measured hepatic triglyceride levels before and after the 2 week dietary intervention. Probably to the surprise of many members of the medical orthodoxy, both groups lost about the same amount of weight (in fact the low-carb group lost -4.6kg, while the low-calorie group lost only -4.0kg!), yet the low-carb group had a much greater reduction in hepatic triglyceride levels:

Liver triglycerides decreased significantly with weight loss (P , 0.001) but decreased significantly more (P = 0.008) in carbohydrate-restricted subjects (-55.6%) than in calorie-restricted subjects (-28.6%).

So, even if you are not particularly interested in your liver health, the fact that by eating to satiety and just dropping your carb intake to <20g/day you can lose the same ~4.5kg you would lose if you starved yourself for 14 days should prick your ears.

Want to Burn More Fat During Your Cardio Training? Eat Low Carb Before Workout!

Modulation of substrate utilization is the key to effective weight loss. For years we have been told that "training in the zone" (referring to a specific heart rate) would do the trick - recent research does yet suggest otherwise: High Intensity Interval Training (HIIT) has been shown to be at least as effective in burning off unwanted body fat, as the longstanding "gold standard", Low Intensity Steady State (LISS) in the "fat burning zone".

Researchers from the Department of Exercise Science and Sports Studies at Springfield College, Springfield, MA, USA, have now found that apart from the type of exercise you chose to perform, the nutrition, especially in the hours before working out, determines whether you will predominantly burn fat or carbs to sustain the workout.

In their study (Gregory. 2011), Gregory et al. compared the metabolic responses of a group of 8 "active, pre-menopausal" women to a 30 minute exercise regimen performed after either a low carbohydrate (LC: 392 kcal @ 15% carbohydrate, 68% fat, and 18% protein) or a low fat (LF: 396 kcal @ 78% carbohydrate, 7% fat, and 15% protein) meal. Respiratory gas exchange (RER), blood glucose (G), insulin (IN), triglycerides (TG), and free fatty acids (FFA) were measured. While "no significant differences existed between test meals for fasting blood measurements", the post-exercise results showed significant differences:

Postexercise (PE) FFA (mEq·L-1) levels were significantly greater following LC [1.1 (0.3) vs. 0.5 (0.3)]. PE TG (mg·dL-1) levels were significantly greater following LC [152.0 (53.1) vs. 114.4 (40.9)]. RER was significantly lower at all time points following LC compared to LF.

With the respiratory gas exchange being a measure of the relative contribution of fatty acids to fulfill the exercise-induced energy demand (Chessex. 1995), the researchers rightly conclude "ingestion of a single LC meal resulted in greater lipid oxidation at rest and during exercise as compared to a single LF meal." But, let's be honest - did you expect anything else?

Overweight Korean Adults Benefit from Protein Rich "Oriental" Diet - More than from Conventional Diet Program.

Americans and Europeans are by no means the only people with unhealthy weight problems. Korea, where the traditional diet is gradually replaced by an Americanized fast-food diet, faces a similar obesity epidemia. The solution, on both sides, appears to be the same: a significant increase in protein intake.

Compared to a 2006 conventional dieting regime the subjects who participated in the 12 week high protein dietary intervention described in a recent study (Joo. 2011) lost more weight (- 4.7 kg vs. -2.3 kg), had a greater reduction in waist circumference (- 6.8 cm vs. 3.3 cm) and lost more body-fat (- 4.2 kg vs. -2.0 kg). In view of the obesity related health issues it is also noteworthy, that...

... the triglyceride reduction was significantly greater (- 30.16 mg/dL, p < 0.001) in the PRO Diet group after intervention compared to the conventional group.

Unfortunately, the original study is missing the dietary guidelines the subjects were provided (the file is not on the server), so you have to content yourselves with the following short summary as to what a "PRO Diet" looks like:

The PRO Diet aims to reduce consumption of refined starches (cooked rice, noodles, white bread) and to encourage the consumption of high protein. Additionally, the PRO Diet encourages the intake of "favorable" carbohydrates with a low glycemic index (GI) and "favorable" fats with high unsaturated fatty acids, while avoiding "unfavorable" carbohydrates with high GI and "unfavorable" fats such as high saturated fatty acids or trans fats.

The old adage of "bad saturated fats" and the hilarous concept of the glycemic index aside, regular visitors of the SuppVersity will recognize these dietary recommendations - certainly no coincidence ;-)

Scientific Evidence Links High Carbohydrate Intake to the Development of Alzheimer's and Other Neurological Diseases

"Fats are bad, carbs are healthy!" I hope nobody out there still believes this late 20th Century slogan. If you do, chances are you will soon forget about it due to the neuronal damage you are inflicting to your brain by eating a high carb diet.

In a very recent review, a group of international scientists (Seneff. 2011) summarize the current state of research as follows:

[...] an excess of dietary carbohydrates, particularly fructose, alongside a relative deficiency in dietary fats and cholesterol, may lead to the development of Alzheimer's disease. A first step in the pathophysiology of the disease is represented by advanced glycation end-products in crucial plasma proteins concerned with fat, cholesterol, and oxygen transport. This leads to cholesterol deficiency in neurons, which significantly impairs their ability to function. Over time, a cascade response leads to impaired glutamate signaling, increased oxidative damage, mitochondrial and lysosomal dysfunction, increased risk to microbial infection, and, ultimately, apoptosis. 

They also compiled a comprehensive list of take-home-massages, some of which may have far reaching consequences:

• Researchers have identified mitochondrial dysfunction and brain insulin resistance as early indicators of Alzheimer's disease.

• ApoE-4 is a risk factor for Alzheimer's disease, and ApoE is involved in the transport of cholesterol and fats, which are essential for signal transduction and protection from oxidative damage.

• The cerebrospinal fluid of Alzheimer's brains is deficient in fats and cholesterol.

• Advanced glycation end-products (AGEs) are present in significant amounts in Alzheimer's brains.

• Fructose, an increasingly pervasive sweetening agent, is ten times as reactive as glucose in inducing AGEs.

• Astrocytes play an important role in providing fat and cholesterol to neurons. [...]

• Glycation damage interferes with the LDL-mediated delivery of fats and cholesterol to astrocytes, and therefore, indirectly, to neurons. [...]

• Synthesis of the neurotransmitter, glutamate, is increased when cholesterol is deficient, and glutamate is a potent oxidizing agent.

• Over time, neurons become severely damaged due to chronic exposure to glucose and oxidizing agents, and are programmed for apoptosis due to highly impaired function. [...]

• Simple dietary modification, towards fewer highly-processed carbohydrates and relatively more fats and cholesterol, is likely a protective measure against Alzheimer's disease.

So, if you have not already forgotten what you just read, make sure to cut back your carbohydrate consumption, limit fructose intake and stop being afraid of fats and cholesterol before you cannot remember anymore.

Lower Protein to Carb Ratio Impairs Akt/TOR Signaling Pathway after Fasting in Rainbow Trout

"Boy, you need your carbs post workout!" This cornerstone of conventional bodybuilding wisdom is crumbling and a new study, if it had been done in humans, not in rainbow trout, would potentially refute this myth once and for all - at least, if one follows the popular (but false) assumption that it is because you are in a carb depleted or overall fasted state after a strenuous workouts.

A group of European scientists (Seiliez. 2011) investigated the effect of diets with different protein to carbohydrate ratios on the Akt/TOR Signaling Pathway after fasting for 48h. What they found contradicts conventional wisdom:

Activation of the Akt/TOR signaling pathway by refeeding was severely impaired by decreasing the proteins/carbohydrates ratio. Similarly, post-prandial regulation of several genes related to glucose (Glut4, glucose-6-phosphatase isoform 1), lipid (fatty acid synthase, ATP-citrate lyase, sterol responsive element binding protein, carnitine palmitoyltransferase 1 and 3-hydroxyacyl-CoA dehydrogenase) and amino acid metabolism (serine dehydratase and branched chain α-keto acid dehydrogenase E2 subunit) only occurred when fish were fed the high protein diet. On the other hand, diet composition had a low impact on the expression of genes related to muscle protein degradation.

So, not only did an increase in carbohydrates negatively impact muscle protein synthesis stimulated by the Akt/TOR signaling pathway, interestingly it also failed to reduce muscle protein degradation, which is the second reason people use in favor of a high carb meal after workouts (/fasting). 

For people following the research and writings of low carb proponents such as Mauro di Pasquale these results may not be surprising. However, before flushing your weight gainer down the toilette, you should really reevaluate your personal and training goals. For an athlete whose exercise bouts are long and frequent, carbohydrate repletion may well turn out to be beneficial. If not for muscle growth, then for performance maintenance. A general demonization of carbs would thus be similarly inappropriate as the "fat scare" of the late 20th century. It all depends on who you are and what your athletic and aesthetic goals are.

Rat Study: High Carb Diet Induces Hepatic Steatosis and Increases Heart Fat by 43%

For a large part of the 1980s and 1990s fats have been considered the "source of all evil". Now, it is our carbohydrate consumption which is held to be responsible for diabetes, obesity and the other ugly faces of "the metabolic syndrom". A recent study by a group of scientists from Sao Paulo (Haubert. 2010) seems to confirm this "revised" hypothesis.

Over a period of 21 days, the scientists fed a group of rats (experimental) a 70% carbohydrate diet with astonishing or rather shocking results (cf. table 1)

 

Within three weeks the rats developed a fatty liver and their heart fat mass increased by 43%. While the scientists did not provide much information about the overall underlying mechanism of these changes, they emphasize the pronounced decline in tissue vitamin E produced by the high carb consumption. In how far additional vitamin E may have prevented some of the fat accumulation yet remains unknown and would warrant further investigation.

Eat Rice, Stay Healthy!?

A recently published study (Fulgoni. 2010) analyzing data from 25 374 eligible participants identified as rice consumers study on the correlation of rice-eating to several markers of metabolic health showed that people who ate at least one serving of rice (white or brown) a day tend to have

better health and diet parameters including less total fat, saturated fat, and added sugars; higher amounts of more than 12 essential vitamins and minerals, including iron, folate, and other B vitamins; more fruit and legumes; nearly 4 tsp (16 g) less added sugar; and 7 g less solid fats. For the 19- to 50-year-old subgroup, main results (P < .05) also showed rice consumption associated with reduced likelihood of being overweight or obese, 34% reduced risk of high blood pressure, 27% reduced likelihood of having an increased waist circumference, and 21% reduced risk of metabolic syndrome.

This, however, should not encourage you to just add one serving of rice to your bad diet habits, because the most important information coming from the study is the first one: Rice eaters tend to have better diet parameters. In other words their general dietary regimen is more healthy, no wonder they have a reduced likelihood of obesity and health issues. Overall, rice is still a very dense source of energy and overeating on it would not be advisable, both from a caloric, as well as (this is more important) from a nutritious point of view - with its high amount of carbohydrate one serving of rice may well amount to all the carbs you may eat, if you follow a heart healthy low carbohydrate diet. Bottom line: Moderation is the key!

Dieting: Nutrient Composition Probably Less Important than On-Going Low vs. High Carb Debate Suggests

In a soon to be published study Kerksick, et.al. (Kerksick. 2010) investigated the effect of 6 dietary regimens on weight loss in 141 obese women (38.7 +/- 8.0 yrs, 163.3 +/- 6.9 cm, 93.2 +/- 16.5 kg, 35.0 +/- 6.2 kg*m-2, 44.8 +/- 4.2 % fat). Interestingly, the members of all groups with restricted dietary intake + exercise achieved similar rates of weight loss (cf. Figure 1)

Figure 1: Changes in weight for High Energy Diet (HED), No Diet (ND), Very Low Carbohydrate High Protein Diet (VLCHP), Low Carbohydrate Moderate Protein Diet (LCMP), High Carbohydrate Low Protein Diet and no diet + no exercise Control (CON)

What I consider most important, though, is the statistical spread of the results. For me this confirms what I have been telling people over and over: There is no "one solution fits it all", it is quite obvious that - from a metabolic point of view - the low insulin level on low carb diets is a major plus (I am a low, but not no-carber, myself). Eating little to no carbs, on the other hand, just does not work out for some, so that they may eventually end up gaining weight instead of losing it (cf. Figure 1).

Bottom line: If you want to lose weight (not fat if you are already lean), eat less calories than you need, exercise and make sure you get proper amounts of nutrients (protein, fats, vitamins and minerals).