Think Muscle - Bodybuilding and Fitness

Carbing Up on the Cyclical Ketogenic Diet

by Lyle McDonald, CSCS
Author of The Ketogenic Diet

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Although ketogenic diets are useful for fat loss, while simultaneously sparing muscle loss, they have one significant drawback: they cannot sustain high intensity exercise. Activities like weight training can only use carbohydrates as an energy source, ketones and free fatty acids (FFA) cannot be used. Therefore the lack of carbohydrates on a ketogenic diet will eventually lead to decreased performance in the weight room, which may result in muscle loss, and carbohydrates must be introduced into a ketogenic diet without affecting ketosis. Probably the most common way to do this is to do a weekend carb-load phase, where ketosis is abolished. During this time period, assuming training volume was sufficient to deplete muscle glycogen (see last article), the body can rapidly increase muscle glycogen levels to normal or supra-normal levels prior to beginning the next ketogenic cycle.

Anyone who has read both "The Anabolic Diet" (AD) by Dr. Mauro DiPasquale and "Bodyopus" (BO) by Dan Duchaine should realize that there are two diametrically different approaches to the carb-up. In the AD, the carb-up is quite unstructured. The goal is basically to eat a lot of carbs, and stop eating when you feel yourself starting to get bloated (which is roughly indicative of full muscle glycogen stores, where more carbohydrate will spill over to fat). In BO, an extremely meticulous carb-up schedule was provided, breaking down the 48 hour carb-up into individual meals, eaten every 2.5 hours. The approach which this article will provide is somewhere in the middle. This article will discuss a variety of topics which pertain to the carb-load phase of the CKD, including duration, carbohydrate intake, quality of carbohydrate intake, fat gain, and others.

Duration and Amount of Carb Load

Arguably the two most critical aspects of a successful carb-load are the duration of the carb-load and the total amount of carbohydrates consumed during this time period. In brief, to achieve optimal glycogen levels, both the duration of the carb-load and the amount of carbs eaten must be correct. The rate limiting step in glycogen resynthesis appears to be activity of the enzymes involved in glycogen synthesis (1). Regardless of carbohydrate intake, there is a maximal amount of glycogen which can be synthesized in a given amount of time. That is to say, consuming all of your carbohydrates in a 4 hour time span, with the goal of returning to ketogenic eating that much sooner, will not work. Only when the proper amount of carbohydrates is consumed over a sufficient period of time, can glycogen compensation and/or supercompensation occur. Following exhaustive exercise and full glycogen depletion, glycogen can be resynthesized to 100% of normal levels (roughly 100-110 mmol/kg) within 24 hours as long as sufficient amounts of carbohydrate are consumed (1,2). Assuming full depletion of the involved muscles, the amount of carbohydrate needed during this time period is 8-10 grams of carbohydrate per kilogram of lean body mass (8-10 g/kg). With 36 hours of carb-loading, roughly 150% compensation can occur, reaching levels of 150-160 mmol/kg of muscle glycogen. To achieve greater levels of muscle glycogen than this (175 mmol/kg or more) generally requires 3-4 days of high carbohydrate eating following exhaustive exercise (3). It should be noted that carb-loading has primarily been studies following endurance training, not weight training and there may be differences in how the body handles carbs following weight training. The first 6 hours after training appear to be the most critical as enzyme activity and resynthesis rates are the highest, around 12 mmol/kg/hour (4). Following weight training, with a carbohydrate intake of 1.5 grams carbohydrate/kg lean body mass taken immediately after training and again 2 hours later, a total of 44 mmol/kg can be resynthesized (4). Over the the first 24 hours, the average rate of glycogen resynthesis ranges from 5-12 mmol/kg/hour depending on the type of exercise performed (5). In general, aerobic exercise shows the lowest rate of glycogen resynthesis (2-8 mmol/kg/hour), weight training the second highest (1.3-11 mmol/kg/hour), and sprint training the highest (15 to 33.6 mmol/kg/hour). (5,6). The reason that glycogen resynthesis is lower after weight training than after sprint training may be related to the amount of lactic acid generated as well as the muscle damage that typically occurs during weight training (5). At an average rate of 5 mmol/kg /hour, approximately 120 mmol/kg of glycogen can be synthesized over 24 hours. This can be achieved with the consumption of 50 grams or more of carbohydrate every 2 hours during the first 24 hours after training. Intake of greater than 50 grams of carbohydrate does not appear to increase the rate of glycogen synthesis. Over 24 hours, at 50 grams per 2 hours, this yields 600 grams of carbohydrates total to maximize glycogen resynthesis. These values are for a 154 pound (70 kilogram) person. Significantly heavier or lighter individuals will need proportionally more or less carbohydrate. Simply keep the value of 8-10 grams of carbohydrate per kilogram of lean body mass as a guide. In the second 24 hours, glycogen resynthesis rates decrease (1) and a carbohydrate intake of 5 grams/kg is recommended to further refill muscle glycogen stores while minimizing the chance of fat gain. For many individuals, the small amount of additional glycogen resynthesis which occurs during the second 24 hours of carbohydrate loading is not worth the risk of regaining some of the bodyfat which was lost during the preceding week.

Type of Carbohydrates

The type of carbohydrate consumed during a carb-up can affect the rate at which glycogen is resynthesized. During the first 24 hours, when enzyme activity is at it's highest, it appears that the consumption of high glycemic index (GI) foods such as simple sugars promote higher levels of glycogen resynthesis compared to lower GI foods like starches (5,7,8). Glycogen resynthesis during the second 24 hours has not been studied as extensively. It appears that the consumption of lower GI carbs (starches, vegetables) promotes higher overall levels of glycogen resynthesis while avoiding fat gain by keeping insulin levels more stable (9). Most individuals find that their regain of bodyfat, as well as retention of water under the skin, is considerably less if they switch to lower GI carbohydrates during the second 24 hours of carbohydrate loading. Fructose (fruit sugar, which preferentially refills liver glycogen) will not cause the same amount of glycogen resynthesis seen with glucose or sucrose (5, 8). Whether liquids or solid carbohydrates are consumed also appears to have less impact on glycogen resynthesis as long as adequate amounts are consumed (10). Anecdotally, many individuals have had success consuming liquid carbohydrates such as commercially available glucose polymers during their first few meals and then moving towards slightly more complex carbohydrates such as starches. Liquid carbohydrates should raise insulin even more than solid carbs, which is useful during the initial hours of the carb-load.

Timing of Carbohydrates

While it would seem logical that consuming dietary carbohydrates in small amounts over the length of the carb-up would be ideal, at least one study suggests that glycogen resynthesis over 24 hours is related to the quantity of carbs consumed rather than how they are spaced out. In this study, subjects were glycogen depleted and then fed 525 grams of carbohydrate in either two or seven meals. Total glycogen resynthesis was the same in both groups. (11) From a purely practical standpoint, smaller meals will generally make it easier to consume the necessary carbohydrate quantities and will keep blood sugar more stable. In Bodyopus, it was recommended that dieters wake up during the night to consume carbohydrates. However this tends to dissuade many dieters from trying the diet at all. The study cited above suggests that eating strictly every 2 hours does not have a large impact on overall glycogen resynthesis rates. Empirical evidence shows that individuals who do not awaken to eat carbs during the night, but consume enough carbohydrates over the length of their carb-up, do achieve glycogen compensation anyway. If an individual must go a long time without eating (i.e. during sleep), a possible strategy is to consume the amount of carbohydrates that would have been consumed during that time period (i.e. 8 hours at 50 grams per 2 hours or 200 grams of carbs over 8 hours) can be consumed at once to keep blood glucose levels and glycogen resynthesis rates as high as possible (5). Consuming these carbs with some protein, fat and fiber will slow digestion and give a more even blood glucose release, helping to promote glycogen resynthesis. Those wishing truly maximal glycogen resynthesis may wish to experiment with eating small carb meals throughout the night.

When to Begin Carb-Up

The carb-up should begin immediately following training. A delay of even 2 hours between the end of training and the start of the carb-up causes glycogen resynthesis to be 47% slower than if carbs are consumed immediately. (10,12). Ideally you should consume a large amount of liquid carbs immediately after training. A good rule of thumb is to consume 1.5 grams of carbs/kg lean body mass, with approximately one half as much protein, immediately after training and then again two hours later. Additionally the consumption of carbohydrates prior to (and even during) the workout prior to your carb-up will lead to higher rates of glycogen resynthesis, most likely as a result of higher insulin levels when the carb-up begins (1,10). It is recommended that individuals consume a small carbohydrate meal approximately 1-2 hours prior to the training session that precedes the carb-up.

Training and the Carb-Up

An important issue regarding the carb-up is the type of exercise that precedes the carb-up. Typical carb-ups have been studied in endurance athletes, not weight trainers so extrapolations must be made with care. It has been long known that only the muscles worked immediately prior to the carb-up are supercompensated. Recall from above that a delay of even several hours slows glycogen resynthesis greatly. Muscle groups which have been trained several days prior to the start of a carb-load will not be optimally supercompensated. This suggests that, for optimal results, the whole body should be worked during the workout prior to the carb-up (this is the basis for the whole body workout on Friday, discussed in the last article). It should be noted that many individuals have achieved fine results not working the entire body prior to the carb-up, using a more traditional split routine workout. Additionally the type of training preceding the carb-up affects the rate and amount of glycogen resynthesized following training. Muscles that have been damaged with eccentric training show lower rates of glycogen resynthesis following training (13,14). However this decrease in resynthesis does not show up immediately. In muscles which have undergone eccentric trauma, glycogen levels are typically 25% lower following a carb-up but this difference does not become apparent until three days after training (or when soreness sets in) (13,14). For individuals performing a 1 or 2 day carb-up, the type of training prior to the carb-up is probably not that critical. For bodybuilders performing a 3 day carb-up prior to a contest, eccentric muscle trauma should be avoided as much as possible.

Other Macro-Nutrients

Another issue regarding the carb-load is the amounts and types of other macronutrients (protein and fat) which should be consumed. The co-ingestion of protein and fat do not affect the levels of glycogen storage during the carb-up as long as carbohydrate intake is sufficient (15). However, many individuals find that fat blunts their hunger and prevents them from consuming enough carbohydrates to refill glycogen stores. Recall that carbohydrate level will be 10 gram/kg lean body mass during the first 24 hours. This will make up 70% of the total calories consumed during the carb load. Preliminary research has shown that a high carbohydrate to protein ratio may increase testosterone (16) and it is suggested that individuals consume 70% carbohydrates, 15% protein and 15% fat during the first 24 hours of their carb-up. Many bodybuilders may feel that this percentage of protein is too low but this is not the case. First and foremost, a high calorie intake reduces protein requirements and increases nitrogen retention (17). As a result, less dietary protein is needed when caloric/carbohydrate intake is high. Protein should be consumed with carbohydrates as this has been shown to increase glycogen resynthesis, especially after training (18). Additionally, combining carbohydrates with protein after weight training raises insulin and growth hormone, which may enhance anabolism (19). Further the most protein lifters need is 1 gram per pound of bodyweight under extremely intensive training conditions (20). Even at 15% protein calories, most individuals will be consuming sufficient protein during the carb-up. Example calculations appear below.

What About Fat Gain?

Possibly the biggest fear many individuals on a ketogenic diet have about the carb-load is the potential to regain body fat due to the high number of calories being consumed (almost double maintenance during the first 24 hours). We will see that fat gain during the carb-up should be minimal as long as a few guidelines are followed. In a study which looked surprisingly like a CKD, subjects consumed a low-carb, high fat (but non-ketogenic) diet for 5 days and depleted muscle glycogen with exercise (21). Subjects were then given a total 500 grams of carbohydrate in three divided meals. During the first 24 hours, despite the high calorie (and carb) intake, there was a negative fat balance of 88 grams meaning that fat was actually lost during the period of high-carbohydrate eating. When muscle glycogen is depleted, incoming carbohydrates appear to be used preferentially to refill glycogen stores, and fat continues to be used for energy production. Additionally the excess carbohydrates which were not stored as glycogen were used for energy (21). In general, the synthesis of fat from glycogen (referred to as De Novo Lipogenesis) in the short term is fairly small (22,23). During carbohydrate overfeeding, there is a decrease in fat use for energy. Most fat gain occurring during high carbohydrate overfeeding is from storage of excessive fat intake (24). Therefore as long as fat intake is kept relatively low (below 88 grams) during the carb-up phase of the CKD, there should be a minimal fat regain. In a similar study, individuals consumed a low-carb, high fat diet for 5 days and then consumed very large amounts of carbohydrates (700 to 900 grams per day) over a five day period (25). During the first 24 hours, with a carbohydrate intake of 700 grams and a fat intake of 60 grams per day, there was a fat gain of only 7 grams. As with the previous study discussed, this indicates that the body continued to use fat for fuel during this time period. In the second 24 hours, with an intake of 800 grams of carbohydrate and a fat intake of 97 grams, there was a fat gain of 127 grams (25) indicating that the body had shifted out of 'fat burning' mode as muscle glycogen stores became full. This is unlike the suggestions being made for the CKD, where the carbohydrate intake during the second 24 hours will be lower than in the first 24 hours. A large fat gain, as seen in this study would not be expected to occur on a CKD. As long as fat intake is kept low and carbohydrate intake is reduced to approximately 5 gram/kg lean body mass during the second 24 hours, fat regain should be minimal. Once again, individuals are encouraged to keep track of changes in body composition with different amounts and durations of carb-loading to determine what works for them. Those looking to maximize fat loss may prefer only a 24 hour carb-up. This allows more potential days in ketosis for fat loss to occur as well as making it more difficult to regain significant amounts of body fat.

How Long Does Glycogen Compensation Last?

Pre-contest bodybuilders (and other athletes) want to know how long they will maintain above normal glycogen levels following a carb-up so that they can time the carb-up around a specific event. With normal glycogen levels, and no exercise, glycogen levels are maintained at least 3 days. (26,27) It appears that above-normal glycogen stores can be maintained at least 3 days as well. (28)

Implications of the carb-load on the adaptations seen in ketosis As discussed in the previous chapters, there are a number of potentially beneficial adaptations which occur during ketosis in terms of decreased protein use and increased fat use. A question which arises is how the insertion of a 1-2 day carbohydrate loading phase will affect these adaptations. To this author's knowledge, no research has examined any effects on ketosis to repeated carbohydrate loading. In general, the adaptations to ketosis take three full weeks in ketosis to occur. A question without an answer is whether these adaptations will take longer, or whether they will occur at all, with repeated carbohydrate loading. Anecdotal experience suggests that they do, but research is needed in this area. Since no physiological measures of the adaptations to ketosis have been measured (except in the short term), it is impossible to make any conclusions regarding the long term adaptations to a CKD. Based on anecdotal reports, it seems that the adaptations do occur, but that they simply take longer. For example, most people starting a ketogenic diet (of any sort) go through a period of low energy, where they are mentally 'fuzzy'. Those who stay on straight ketogenic diet (no carb-load) generally move past this stage by the second or third week of dieting. In contrast, those on a CKD seem to take slightly longer to overcome this feeling. As a personal example, this author experienced a great deal of fatigue in the first week of being on a CKD, a smaller (but still above baseline) amount of fatigue during the second week, and essentially no fatigue on the third week. This suggests (but requires further research) that the adaptation of the brain to ketosis may take slightly longer due to the insertion of a carb-load phase. This also suggests that individuals may want to do two weeks of an CKD prior to their first carb-up, to allow the adaptations to occur more quickly. Of course, if this compromises training intensity, it is not a viable option.

Adjustments to the Carb-Load

To a great degree, the carb-load can be the part of the CKD which either makes or breaks the diet. A balance must be struck between carb-loading enough to support intense weight training without gaining back the bodyfat lost during the previous week. Many individuals do well with an unstructured approach to the carb-load. They simply eat a ton of carbs, get some protein and fat in there, and do just fine. However for many individuals this does not work well and there is too much fat spillover during the carb-load, making the CKD a 2 steps forward, 1 step backwards ordeal. In this case, the following modifications can be made.

1. Shorten the length of the carb-load. Considering that the body stays in a 'fat burning' mode for at least the first 24 hours of the carb-load, any carb load shorter than 24 hours should make it generally impossible to gain appreciable fat. In fact some individuals have had success with the CKD buy doing 2 24 hour carb-load phases during the week, for example on Wednesday and Sunday.

2. Clean up the carb-load. While part of the attraction of the CKD is the ability to eat whatever you want during the carb-load, a steady diet of donuts and chicken wings on the weekend can short-circuit fat loss. Making better food choices, starting with high GI carbs and moving to more complex starches as the hours pass, can make all the difference between a successful and an unsuccessful fat loss CKD.

3. Watch total macronutrient intake. Although it's a bit of a pain, monitoring total carb, protein and fat intake during the carb-load can help prevent fat spillover, especially when coupled with strategy #2.

4. Use specific supplements like Citrimax and Alpha-lipoic acid. Although the human data on Citrimax (the trade name for hydroxycitric acid) is few and far between, empirical evidence suggests that it's use during the carb-load significantly decrease carb spillover to fat and leads to better carb-loads. Additionally, Citrimax tends to blunt hunger and can help to prevent overeating during the carb-up. A dosage of 750-1000 mg taken three times daily, at least 30 minutes before meals, is the recommended dose. Additionally, alpha lipoic acid (ALA) is an anti-oxidant and glucose disposal agent (29) which has shown great use during carb-ups for many individuals on the CKD. In comparison to chromium, magnesium and vanadyl sulfate, ALA appears to work significantly better. A dosage of 200-600 mg per day is a good place to start as far as dosage but be forewarned that it can get expensive quickly.

Summary of Guidelines for the Carb-Load

1. 8-10 grams of carbohydrates per kilogram of lean body mass should be consumed during the initial 24 hours of the carb-load. This will make up 70% of the total calories consumed. During the second 24 hours, approximately 5 grams/kg should be consumed which will be approximately 60% of the total calories consumed.

2. Protein intake should be approximately 1 gram per pound during all phases of the carb-load. In the first 24 hours, this will represent about 15% of total calories, in the second 24 hours, this will represent about 25% of total calories.

3. Fat intake should be kept at 15% of total calories during the first 24 hours, or a maximum of 88 grams of fat. Fat intake should be roughly cut in half during the second 24 hours of the carb-load.

Sample calculations for a carb-load for different body weights So simplify the calculations for the carb-load, the following charts give approximate amounts of protein, fat, carbohydrate, and total calories for the carb-load phase, based on different amounts of lean body mass.

During the first 24 hours of carb-loading, carbohydrate intake should be 10 grams per kilogram of lean body mass or 4.5 grams of carbs per pound of lean body mass . This will represent 70% of the total calories consumed. The remaining calories will be divided evenly between fat (15% of total calories) and protein (15% of total calories). Figure 1 gives estimated amounts of carbohydrate, protein and fat for various amounts of lean body mass.

Figure 1: Summary of nutrient intake during first 24 hours of carb-loading
Lean body mass (pounds) Carb (grams) Fat (grams) Protein (grams) Total calories*
100 450 43 98 2600
120 540 51 115 3100
140 630 60 135 3600
160 720 68 153 4100
180 810 76 172 4600
200 900 85 193 5100

* The total calories consumed during the first 24 hours of the carb-load will be approximately twice what was being consumed during the lowcarb week.

During the second 24 hours of carb-loading, carbohydrates will make up 60% of the total calories, protein 25% and fat 15%.

Figure 2: Summary of nutrient intake during second 24 hours of carb-loading  
Lean body mass (pounds) Carb (grams) Fat (grams) Protein (grams) Total calories
100 227 20 90 1448
120 270 25 108 1737
140 310 30 126 2014
160 360 35 144 2331
180 405 40 162 2628
200 450 45 180 2925

Once again, the above amounts should be considered guidelines only. Experimentation coupled with good record keeping will help an individual determine the optimal amounts of nutrients to consume during their carb-up.


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