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Part II
Ketogenic Diets
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Introduction
In the last article, we covered some basic dietary aspects specific to the goal of improving body composition. We are now going to go into more detail on the specifics, and the next few articles will discuss the most focused-on topic among dieters today, macronutrients.
The term macronutrients generally refers to the nutrients in our food that provide calories, which fall into four general categories: fat, carbohydrates, protein, and alcohol. We aren't going to talk much about alcohol here except to say that you should obviously limit intake if you are concerned with body composition. Fats provide 9 calories (technically kilocalories, but general usage is to refer to them as calories) per gram, while protein and carbohydrates each provide 4 calories per gram. There are exceptions, but these numbers are the important ones to remember.
These articles are going to focus on weight loss. While macronutrients are certainly important during periods of weight gain, there is much less debate about them, and it is generally agreed upon that all three should be consumed in adequate quantities during this period. While we will certainly discuss the ideal amounts of macronutrients to consume during periods of weight gain or maintenance, weight and fat loss will be the central issue during most of the discussion of macronutrients.
The Keys to Weight Loss
What is the single most important factor in a successful weight loss diet? Some will say, "low fat." Some will say, "low carb," or "low sugar." The correct answer is "low calorie." You can cut out all the fat in your diet, or you can cut out all of the carbs, you could even cut both, and you still wouldn't consistently lose weight unless your caloric intake was below maintenance level. This isn't to say that altering macronutrient ratios can lead to weight loss independently of caloric intake (we will see some studies that indicate that this can work below). It just means that results will not be consistent unless caloric intake is low. So, if one is having extreme difficulty losing weight, the first step should always be to start keeping track of calories.
What is the second most important factor determining weight loss? Again, it is not the macronutrients you consume. It is exercise. This isn't a training article so we won't go into specifics, but eating less and exercising are the simple fundamentals of weight loss. Everyone knows this, but they all too often are ignored – people stop eating carbohydrates and take twenty supplements and expect weight loss to be automatic. It is a good idea to concern yourself both with these and eating the right macronutrients and foods. However, if you only concern yourself with macronutrients and ignore these two fundamentals, your efforts are not likely to yield any significant results.
Ketogenic Diets
When discussing macronutrient manipulation, this is the best place to start, as ketogenic diets are the most extreme. Although it is not commonly realized, there are essentially two types of low carb diets. The first is simply a diet classified as "low carbohydrate," which generally refers to diets where less than 45% of calories come from carbohydrates, less than the minimum recommendation of most health organizations (which usually falls in the 45-55% range). We will discuss these further later on. The second type is classified as "very low carbohydrate" or "ketogenic," usually defined as less than 10% of calories coming from carbohydrates or less than 50 grams of carbohydrates daily.
Ketogenic diets, which were originally used to control epilepsy and some other disorders in children, are uniquely different from low carbohydrate diets where carbohydrate intake isn't restricted quite as much. On a ketogenic diet, the state of carbohydrate deprivation is extreme enough that the body begins producing large amounts of "ketones," a fuel derived primarily from fat, as a substitute.
There are a number of potential reasons why ketogenic diets can be beneficial for fat loss. For one, the primary ketone produced, beta-hydroxybutyrate, may act as an appetite suppressant. Since a ketogenic diet is almost inevitably low glycemic, rapid changes in blood sugar levels are prevented and insulin levels are reduced. Because ketones and protein are both generally used only in low amounts as energy sources during exercise, a ketogenic diet can increase the use of fat as a fuel source during aerobic exercise. Ketones are also generally a less efficient fuel source, increasing the number of calories burned relative to the number consumed.
In addition to the long list of possible benefits, the research on ketogenic diets is equally as impressive. For example, in one of the most recent studies [1], overweight or obese men and women (averaging 30-35 years of age) were put on either a ketogenic diet (10% carbohydrate, 60% fat, 30% protein) or a standard diet (55% carbohydrate, 25% fat, 20% protein), each with a 500 calorie deficit, for periods of a month or more. The foods used by both groups were generally healthy.
According to dietary records, the group on the ketogenic diet ended up consuming more calories (about 250 more daily than the other group). Despite this, the group on the ketogenic diet lost more weight. Much more importantly, the percentage of weight lost from fat was greater in the group on the ketogenic diet, indicating a greater degree of lean tissue preservation. Additionally, the proportion of trunk fat lost was greater on the ketogenic diet by a three-fold degree. In summation, the ketogenic diet yielded greater weight loss, greater muscle preservation, and a greater proportion of fat lost from the region that people strive most to lose fat from.
A number of other studies have been conducted in the past few decades, and although not all of them have had the same findings regarding weight loss and preferential loss of fat, the majority have. Regarding nutrient partitioning effects, one meta-analysis indicated that the average percentage of weight lost from fat on a normal diet is 71%. While there probably aren't enough studies on ketogenic diets to pool the results in the same fashion, one article lists the percentage of weight lost from fat on ketogenic diets from various studies as 97%, 95%, and 80% [1]. It is clear from this and other research that ketogenic diets are more muscle-sparing than traditional diets.
One of the most important studies is one that is closer to applying to bodybuilders, as it used subjects that were not overweight or obese. Normal-weight men were either put on ketogenic (8% of energy from carbohydrates) diets or served as controls for six weeks and told to eat enough to maintain their body weight. In the control group, there were no significant changes in body composition. In the group that consumed the ketogenic diet, fat mass was decreased by 7.5 lbs and lean mass was increased by 2.4 lbs at the end of the six weeks [2]. This indicates that, even in normal individuals, ketogenic diets can have positive nutrient partitioning effects.
The Problems with Ketogenic Diets
Ketogenic diets seem to be everything a bodybuilder could want. So, why isn't everyone on a ketogenic diet?
Well, the primary problem with ketogenic diets, both for bodybuilders and for everyone else, has to do with sustainability. Most of the studies on ketogenic diets have been short-term, usually a matter of weeks. There have been longer studies, usually offered as arguments for the sustainability of ketogenic diets, but when one takes a look at these studies, dietary compliance among the subjects was rather low. In one six month study, subjects instructed to get less than 15% of their calories from carbohydrates ultimately ended up increasing their intake to 30% at the end of the study, whereas compliance in the normal, reduced-calorie group was relatively high. It is noteworthy that weight loss was still significantly higher in the low carbohydrate group in this study. Similarly, in another six month study, subjects instructed to eat less than 30 grams daily of carbohydrates ended up getting 37% of their calories from carbohydrates. In a more recent six month study, only some patients were instructed to keep dietary records, which indicated good compliance with the low carbohydrate diet. However, urinary ketone levels taken during the third and six month indicated poor compliance [3].
The difficulty of sustaining a ketogenic diet may not worry some bodybuilders. Indeed, bodybuilders are known for their resolve in keeping strict dietary practices. However, one cannot ignore the psychological side of the equation. To stay in ketosis, one cannot eat extra carbohydrates, or they will come out of ketosis (usually for a few days, although this can be accelerated through various means). In other words, one slip-up becomes a significant setback. For most people, a ketogenic diet would require not eating many of their favorite foods. It also means bad breath and body odor due to the ketones, something most people do not want.
In addition to the sustainability issue, there is the issue of health. This is an issue on which there is fierce debate, on the one hand, people citing studies indicating that ketogenic diets improve blood lipid profiles, and on the other, people listing the nutrients which ketogenic diets tend to lack. There is the generic "high fat diets are unhealthy" argument, but that does not carry much weight, given that the type of fat is often more important than the quantity. The possible nutrient deficiencies due to ketogenic diets most commonly cited are fiber, potassium, and some B vitamins. Additionally, ketogenic diets can produce a high acid load. However, as long as care is taken to get these nutrients and fruits and vegetables are used as the primary source of carbohydrates, ketogenic diets should not pose much of a health risk. Unlike fat and protein, carbohydrates are not a necessary aspect of the human diet. That isn't to say that a low carbohydrate diet is optimal for good health, just that it isn't necessarily detrimental.
Problems Specific to Athletes
The problem with ketogenic diets for bodybuilders may not lie in the issue of health, or even in the issue of sustainability. Rather, the problem is that carbohydrates are of great value to bodybuilders, and athletes in general. It is important to note that bodybuilders have many things to take in to consideration that the average person does not, and the studies discussed above must be viewed in this light.
Most important is the issue of glycogen. Glycogen is the primary fuel used by muscle tissue during short periods of high intensity exercise, including resistance training [4], and if glycogen stores are inadequate, a workout can be hindered. The amounts of carbohydrates that are necessary to keep sufficient glycogen stores in someone who is resistance training may not be as high as one might think, but they are certainly higher than a ketogenic diet allows for.
Many studies on endurance athletes have found that low carbohydrate, high fat diets can significantly improve endurance exercise performance. However, the way the body utilizes fuel during exercise and the factors governing exercise performance are significantly different during resistance training. Also, other studies have found a decrease in endurance performance during low carbohydrate dieting [5]; the different results are probably due to varying study protocols.
There are fewer studies on the effects of low carbohydrate intake on high-intensity, intermittent forms of exercise which are closer to weight lifting, but there are enough to establish a decrease in performance for this type of exercise [6-9]. For example, in one study [8], subjects consumed a standard diet (50%, 30%, and 20% carbohydrates, fat, and protein respectively) or a ketogenic diet (5%/50%/45%) for three days. Ketone concentrations were about ten times higher among those who went on the ketogenic diet after this period. Both groups performed high intensity exercise lasting 30 seconds, and in those who consumed the low carbohydrate diet, performance was significantly decreased. One of the conclusions of the authors was, "a L-CHO [low carbohydrate] diet is detrimental to anaerobic work capacity, possibly because of a reduced muscle glycogen store and decreased rate of glycolysis."
One argument might be that although performance is decreased, fat utilization is significantly higher during exercise on a ketogenic diet. Although this is true, it is probable that protein utilization will also be higher, particularly during resistance training (during which the rate of protein turnover is high), which is an inherent tradeoff. Also, the importance of maximizing fat burning during exercise (as opposed to metabolic changes resultant of exercise) is overrated. In either case, it is valuable to maintain performance during a diet, as a decrease in performance could ultimately result in a greater decrease in muscle mass.
Maintenance of muscle glycogen stores isn't the only benefit carbohydrates have to offer. Carbohydrates taken before exercise can increase the net protein synthetic response from a workout, maintain performance through mechanisms other than glycogen preservation such as positive effects on the central nervous system and maintaining blood sugar levels, prevent the rise in circulating tryptophan (which can contribute to perceived exertion and fatigue), and prevent the rise in cortisol (a hormone that is catabolic to muscle tissue) [10-12].
Given all of this, ketogenic dieting does not seem to be the best option for a bodybuilder. The exception might be during the pre-contest period, or when rapid fat loss is desired and performance is not a priority. Even then, one would not want to go on a ketogenic diet for an extended period of time.
Cyclical ketogenic diets
Cyclical ketogenic diets (CKD's) were created as an alternative to traditional ketogenic diets, and for the most part, they have been the invention of bodybuilders and used primarily by bodybuilders (there is little, if any reference to them in the scientific literature, although there are scientific principles behind the ideas that are employed). The general idea of a CKD is that most of the week is spent in ketosis, with a weekly "carb load" period to refill glycogen stores. Thus, one gets the best of both worlds, in theory.
In reality, while CKD's will surely be effective for weight loss, one cannot really say if they have a significant advantage over other diets, because the basic ideas are pieced together from research that may or may not apply. There are benefits that are relatively certain (such as the benefits of carb loading), but there are also drawbacks that are relatively certain (such as the fact that most of the week, performance in the gym will be lower), so it is difficult to say which outweighs. There are plenty of people who swear by them, but it is difficult to make judgements based on personal feedback, given that many people experience results just by paying close attention to what they eat, which a CKD necessitates.
We are not going to go in-depth on CKD's, although a number of books have been written on the topic. A specific set of dietary and exercise protocols are required, especially around the period of the carb load. Those who are more experimental and dedicated may want to give a CKD a try. However, the idea behind this series is to keep it simple where possible, and a complex set of protocols is not warranted unless there is strong scientific evidence that it is worthwhile. By strong scientific evidence, I refer to the specific set of protocols being tested in a controlled setting, not extrapolations from different studies pieced together. Too many trends have come and gone for armchair science to be considered reliable, and what we are looking for here is guaranteed results without the extra baggage. Other issues are that the variety of foods you can eat is still limited on a CKD and that such a diet is difficult to sustain.
Conclusion
In this article, we discussed one of the most popular types of diets based on macronutrient ratios, the ketogenic diet. Although such a diet may not be optimal for most, there are still some important points to take away from this discussion. The first is that, given the success of ketogenic diets, there may be reason to limit carbohydrate intake, just to a less drastic extent. The second is that a minimum level of carbohydrate intake is going to be desirable to maintain performance and glycogen levels. Third, we have seen that although caloric intake is the most important factor in a diet, there is definite potential to alter the muscle to fat ratio through dietary means, independently of caloric intake.
In the next section of this series, we will continue the discussion of macronutrient ratios, and come to some more solid conclusions regarding an optimal range for each macronutrient in the diet.
References
1. Nutr Metab (Lond). 2004 Nov 8;1(1):13 [Epub ahead of print]. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Volek JS, Sharman MJ, Gomez AL, Judelson DA, Rubin MR, Watson G, Sokmen B, Silvestre R, French DN, Kraemer WJ.
2. Metabolism. 2002 Jul;51(7):864-70. Body composition and hormonal responses to a carbohydrate-restricted diet. Volek JS, Sharman MJ, Love DM, Avery NG, Gomez AL, Scheett TP, Kraemer WJ.
3. Best Pract Res Clin Gastroenterol. 2004 Dec;18(6):1031-47. Is there an optimal macronutrient mix for weight loss and weight maintenance? Wilkinson DL, McCargar L.
4. Sports Med. 2004;34(5):317-27. Macronutrient considerations for the sport of bodybuilding. Lambert CP, Frank LL, Evans WJ.
5. Eur J Appl Physiol Occup Physiol. 1987;56(4):444-50. Dietary composition and acid-base status: limiting factors in the performance of maximal exercise in man? Greenhaff PL, Gleeson M, Whiting PH, Maughan RJ.
6. Acta Physiol Scand. 1999 Apr;165(4):337-45. High-intensity exercise and muscle glycogen availability in humans. Balsom PD, Gaitanos GC, Soderlund K, Ekblom B.
7. Int J Sport Nutr Exerc Metab. 2003 Dec;13(4):466-78. Endurance capacity and high-intensity exercise performance responses to a high fat diet. Fleming J, Sharman MJ, Avery NG, Love DM, Gomez AL, Scheett TP, Kraemer WJ, Volek JS.
8. Eur J Appl Physiol Occup Physiol. 1997;76(2):128-33. The effect of a low-carbohydrate diet on performance, hormonal and metabolic responses to a 30-s bout of supramaximal exercise. Langfort J, Zarzeczny R, Pilis W, Nazar K, Kaciuba-Uscitko H
9. Eur J Appl Physiol Occup Physiol. 1996;72(3):249-55. The effect of glycogen availability on power output and the metabolic response to repeated bouts of maximal, isokinetic exercise in man. Casey A, Short AH, Curtis S, Greenhaff PL.
10. J Physiol. 2000 May 15;525 Pt 1:271-81. Effect of oral glucose on leucine turnover in human subjects at rest and during exercise at two levels of dietary protein. Bowtell JL, Leese GP, Smith K, Watt PW, Nevill A, Rooyackers O, Wagenmakers AJ, Rennie MJ.
11. J Appl Physiol. 2000 Dec;89(6):2220-6. Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance. Febbraio MA, Chiu A, Angus DJ, Arkinstall MJ, Hawley JA.
12. Amino Acids. 2001;20(1):25-34. Amino acids and central fatigue. Blomstrand E.