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Team MD'S #1 CONTEST COVERAGE

 

Fat Attack

By Dan Gwartney, MD

 

Ketogenic Diets Safe and Effective

Good News for the Midsection from the Mid-East

 

The U.S. has a growing problem, one that's increasingly affecting other countries, as well. Americans, as well as citizens of many other nations, are failing to maintain a healthy weight.1 In fact, the number of obese and overweight individuals worldwide is growing at an alarming rate. As the population of obese grows, so, too, does the burden upon the health care system and the global economy. Obesity is not just an aesthetic challenge; it's associated with many of the major health risks facing individuals and society. One report, published in 1993, stated that 300,000 people in the U.S. died from obesity-related causes every year.2 Bear in mind, the incidence of overweight and obesity has increased in the last decade. This number is likely higher and will continue to worsen until a major shift in lifestyle is achieved.

 

            Fat as Fuel Source

The established doctrine from dieticians and the American Heart Association continues to rely upon the low-fat diet.3 Yet, time and again, the regimens of eating a carbohydrate-rich diet in order to avoid foods high in fat have failed to provide any true benefits in controlled clinical trials. During the last several years, high-protein diets have come into vogue, accompanied by best-selling books and talk show segments. Perhaps because they challenge the establishment, the founders of these movements are often labeled charlatans and renegades.4 Yet, in most cases, these new approaches are created by physicians or scientists who have clearly seen the failing of the low-fat diets. Today, programs like the Zone, Atkins and South Beach diets are household words. Literally millions of people have tried these diets, many experiencing a degree of weight loss they never enjoyed before.

            An initial phase is common to several of these diets, in which carbohydrates are severely restricted. Taking carbohydrates from the diet removes outside sources of sugar, the main energy source for most cells of the body. When sugar levels remain chronically low, the body undergoes a metabolic shift, utilizing fatty acids for the main energy source.5 Fatty acids come from fat cells, where they are stored as triglycerides, a group of three fatty acids sharing a common storage backbone (glycerol). When the body is under stress, hormonal signals trigger a series of reactions in the fat cell (adipocyte) freeing the fatty acids from glycerol, allowing them to be delivered to active tissues, such as the heart, liver and muscle.6

            Under normal conditions, fatty acids are used as a minor fuel source with no noticeable consequences. However, when forced to rely heavily upon fatty acids as the main fuel source, the body enters a state called ketosis. Ketosis is a term describing the presence of ketone bodies in the blood. Ketone bodies are produced primarily in the liver as a result of incomplete fatty acid oxidation.7 For the sake of comparison, think of burning a molecule of a fatty acid like it is a log being burned in the fireplace. Once the log is done burning, there is always some ash, which is actually parts of the wood that were incompletely oxidized (burned). It's much the same with fatty acids. The more fatty acids you burn, the more ketones (ash) you produce.

            Ketones were once thought to be a waste product, but it was discovered that they serve a very valuable purpose. The brain is highly dependent upon glucose (sugar) for energy. When glucose levels drop, the brain enters a crisis mode and signals a stress condition to the body. Under the influence of adrenalin, glucagon, growth hormone, cortisol and other hormones, the liver and other tissues are stimulated to release stored sugars. However, after approximately three days of restricted carbohydrate intake (usually less than 30 grams per day), liver stores of glucose have been depleted. During this time, the metabolism shifts over to relying primarily upon fat (and amino acids to a small degree) to produce energy. Ketones build up during this time and are released into the bloodstream.7

            The nerve cells of the brain are unable to metabolize fatty acids for energy and unless an alternative source was available, the body would go into shock. This type of shock is seen in people with uncontrolled diabetes, as sugar levels will plummet suddenly. Fortunately, for healthy people, there is an alternative. The brain can use ketones as a fuel source, allowing previous generations to survive periods of famine or fasting.8 During the initial period, many people find adjusting to ketosis to be uncomfortable, most complaining of lethargy and fatigue. However, once the body has adapted to the new environment, a comfortable lifestyle is possible.

 

            The Ketogenic Diet Evaluated

            Though the concept and practice of a ketogenic diet has been in existence since 1920, the general consensus of the medical community was that it was too dangerous to recommend unless medically necessary.4,9 Interestingly, ketogenic diets have been used to manage several conditions, including epilepsy, better than many drug treatments. Despite being used safely and effectively to treat maladies in adults, children and infants, it was long considered to be in poor professional judgment to prescribe its use to otherwise healthy individuals.

            Only in the last decade has the ketogenic diet been studied and evaluated as a weight loss tool. Remember, the condition of obesity did not receive much attention from researchers until the latter half of the twentieth century. Anecdotal reports from studies following patients utilizing ketogenic diets to control medical conditions had long reported weight loss, but this was largely ignored. Additionally, there was great resistance against this type of diet as it relied upon a high percentage of fat. Dieticians and cardiologists refused to accept that a high-fat diet could be anything other than atherogenic, meaning they suspected it would cause cardiovascular disease. Also, as fat is over twice as calorie-dense as carbohydrates, logic seemed to dictate that weight gain would be the expected outcome.

            Surprisingly, early studies demonstrated the exact opposite. Ketogenic diets, despite having a high fat content, appeared to reduce cardiovascular risks. Further, subjects on ketogenic diets consistently lost more weight.10 As per usual, the common edict was stamped on each study stating it was inconclusive as it only looked at short-term results.

            No longer is this the case. Several long-term studies have been published in prestigious, peer-reviewed journals.11-14 One, a paper recently published in the journal Experimental and Clinical Cardiology by researchers from Kuwait University who completed a six month study, followed 83 healthy, obese men and women on a ketogenic diet.14 For the first 12 weeks, the subjects were restricted to 20 to 30 grams of carbohydrate per day, increasing to 40 to 50 grams per day for the second 12-week period. The subjects were assigned a diet containing green vegetables and salad, various protein sources providing 80 to100 grams of protein daily (one gram per kilogram of bodyweight per day) and a multivitamin. During the 24-week period, each subject's weight dropped considerably, approximately 33 pounds on average. Investigators also documented changes in the cardiovascular risk profile and kidney function.

            Despite eating a high-fat diet, the subjects saw significant reductions in cardiovascular risk. Levels of triglycerides (blood fat) and cholesterol dropped significantly, including a mild reduction in LDL (bad) cholesterol; HDL (good) cholesterol actually rose during the treatment period. Blood glucose (sugar) was dramatically lower, as was to be expected. Kidney function, as measured by creatinine and urea levels, was unaffected.

            This study is important, as it shows that in healthy, obese people, ketogenic diets can be followed for longer periods with no apparent adverse effects. The investigators stated this rather boldly in claiming, "... the present study confirms that it is safe to use a ketogenic diet for a longer period of time than previously demonstrated."14 Though this may be true, most professionals will want to see supporting studies reaching the same conclusion. For those with an open mind, the studies published in the preceding years should allow for acceptance of the claimed safety of ketogenic diets for a six month period.1113 For those with a closed mind, stone tablets brought down from Mt. Sinai would likely not sway their opinion.

 

            Proceed with Caution

Even though these studies are impressive and persuasive, caution needs to be advised to people considering a ketogenic diet. It's important to realize that the diet needs to be structured correctly. Calories need to be restricted to sub-maintenance value to avoid consuming excess calories and gaining weight. Also, the types of fats used in these studies emphasized the inclusion of polyunsaturated and mono-unsaturated fats, which may have accounted for some of the cardiovascular protection.15 Eating large quantities of saturated fat (usually animal fat) is considered to be detrimental to heart health.

            Carnitine is a micronutrient that aids in fatty acid oxidation. Ketogenic diets increase the demand for carnitine as the rate of fatty acids being burned for calories escalates.7 Carnitine is often supplemented in therapeutic ketogenic diets to avoid a potential deficiency.

            For athletes, there are other issues to consider, as well. Sugar is the short-term energy source, so a ketogenic diet may impair performance.16 If a ketogenic diet is chosen, it would be wise to log and evaluate the number of carbohydrate grams needed to maintain ketosis, but allow for an acceptable level of performance. This can be done by using keto-stix, coated tabs of paper that turn color if ketones are present in the urine. Sedentary people require a low carbohydrate intake to maintain ketosis, but for active individuals, that number may be two to three times as high. Of course, the carbohydrates will need to be ingested near the period of exercise. It has been reported that substitution of glutamine in place of sugar still allows for glycogen replenishment in the muscles after a workout, though this has been disputed.17

            Insulin has fallen under the scrutiny of the popular press, being a central hormonal figure in gaining fat. Insulin is released from the pancreas in response to dietary carbohydrates. Thus, ketogenic diets are associated with low blood levels of insulin, due to the low dietary carbohydrate content.12

            However, athletes need to consider that insulin is also vital to gaining muscle. One recent review on skeletal muscle hypertrophy (growth) presents a strong argument for insulin being essential for muscle growth.18 It's very common for athletes and bodybuilders to report mild to exaggerated decreases in strength and muscularity while on a ketogenic diet. This may be due in part to a relationship between blood sugar and testosterone; when blood sugar levels remain low, testosterone levels also drop.19 For some, it's a tolerable price to pay for a leaner physique. Others will abandon the ketogenic diet, desiring to maintain or increase their strength or size in preference to fat loss.

            Though nearly all controlled studies have found ketogenic diets to be safe and well tolerated with no adverse effects, some individuals have experienced kidney stones, changes in heart rhythm, nausea and bad breath.11,20-22 Though many studies have documented a mild, non-significant reduction in LDL (bad) cholesterol, others have found no effect; some even noted a slight elevation in this value in some subjects.11 Given the diversity of response and increased risk with elevations in LDL cholesterol, it would be prudent to seek basic supervision from a physician. This is particularly important for those already at increased risk of heart disease or stroke, as well as those with a strong family history for such events. The esteemed physician, Dr. Dean Ornish, cautions against recommending a low-carbohydrate diet due to the lack of fruits, vegetables and whole grains.23

            In addition to impaired physical performance, cognitive (mental) performance often becomes sluggish, as well. This is especially true during the initial weeks as the body adjusts to the low-carbohydrate environment. Irritability, poor job performance, forgetfulness and lower grades may result.24

 

            Is a Ketogenic Diet for You?

Ketogenic diets are extremely effective. Establishing a ketogenic lifestyle is difficult, as the body struggles with the onset of ketosis, reacting to it as a threatening event. Though ketogenic diets have been used in patients of all ages for nearly a century, only recently have studies been reported demonstrating the safety and efficacy of ketogenic diets for weight loss in healthy, obese adults. To establish ketosis, a rigid discipline is necessary, with vigilance to the many hidden sources of carbohydrates- such as medicines- in our daily lives.25 The ultra-low carbohydrate allowances make the ketogenic diet insufferable to many sedentary people.

For athletes, it is even more difficult, as a low blood sugar negatively affects athletic performance and may reduce or prevent muscle growth in response to exercise. Many people complain of lethargy and fatigue, making it difficult to perform well at work or school. Despite the studies reporting no adverse effects with the use of ketogenic diets, some negative effects have been documented, including kidney stones, nausea and changes in heart rhythm. Yet, the health benefits of a ketogenic diet, particularly diets rich in polyunsaturated and mono-unsaturated fats, have been repeatedly demonstrated in controlled clinical trials.

            The choice of diet will depend heavily upon the preferences and needs of the individual. However, recent and ongoing research is making it increasingly evident that the role of carbohydrates in the diet needs to be re-evaluated. Though soft breads and sweet candies are wonderful treats, they appear to offer no benefits in regard to health or weight loss. Instead, the traditional staples of the American diet- bread, pasta and potatoes- may also be health risks. 

 

References 

  1. Bray GA. Medical consequences of obesity. J Clin Endocrinol Metab, 2004 Jun;89(6):2583-9.
  2. McGinnis JM, Foege WH. Actual causes of death in the United States. JAMA, 1993;270:2207-12.
  3. Krauss RM, Eckel RH, et al. AHA Dietary Guidelines: revision 2000: A statement for healthcare professionals from the Nutrition Committee of the American Heart Association. Circulation, 2000 Oct 31;102(18):2284-99.
  4. Astrup A, Meinert Larsen T, et al. Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss? Lancet, 2004 Sep 4;364(9437):897-9.
  5. Westman EC, Mavropoulos J, et al. A review of low-carbohydrate ketogenic diets. Curr Atheroscler Rep, 2003 Nov;5(6):476-83.
  6. Merl V, Kern W, et al. Differences between nighttime and daytime hypoglycemia counterregulation in healthy humans. Metabolism, 2004 Jul;53(7):894-8.
  7. Sankar R, Sotero de Menezes M. Metabolic and endocrine aspects of the ketogenic diet.
  8. Guzman M, Blazquez C. Ketone body synthesis in the brain: possible neuroprotective effects. Prostaglandins Leukot Essent Fatty Acids, 2004 Mar;70(3):287-92.
  9. Wilder RM. The effect of ketonemia on the course of epilepsy. Mayo Clin Proc, 1921;2:307-8.
  10. Sharman MJ, Kraemer WJ, et al. A ketogenic diet favorably affects serum biomarkers for cardiovascular disease in normal-weight men. J Nutr, 2002 Jul;132(7):1879-85.
  11. Yancy WS, Olsen MK, et al. A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia: a randomized, controlled trial. Ann Intern Med, 2004 May 18;140(10):769-77.
  12. Samaha FF, Iqbal N, et al. a low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med, 2003 May 22;348(21):2074-81.
  13. Brehm BJ, Seeley RJ, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrinol Metab, 2003;88(4):1617-23.
  14. Dashti HM, Mathew TC, et al. Long-term effects of a ketogenic diet in obese patients. Exp Clin Cardiol, 2004;9(3):200-5.
  15. Fuerhrlein BS, Rutenberg MS, et al. Differential metabolic effects of saturated versus polyunsaturated fats in ketogenic diets. J Clin Endocrinol Metab, 2004 Apr;89(4):1641-5.
  16. Ivy JL. Muscle glycogen synthesis before and after exercise. Sports Med, 1991 Jan;11(1):6-19.
  17. van Hall G, Saris WH, et al. The effect of free glutamine and peptide ingestion on the rate of muscle glycogen resynthesis in man. Int J Sports Med, 2000 Jan;21(1):25030.
  18. Kimball SR, Farrell PA, et al. Role of insulin in translational control of protein synthesis in skeletal muscle by amino acids or exercise. J App Physiol, 2002 Sep;93(3):1168-80.
  19. Hypoglycemia, but not insulin, acutely decreases LH and T secretion in man. J Clin Endocrinol Metab, 2001 Oct;86(10):4913-9.
  20. Best TH, Franz DN, et al. Cardiac complications in pediatric patients on the ketogenic diet. Neurology, 2000 Jun 27;54(12):2328-30.
  21. Rios VG. Complications of treatment of epilepsy by a ketogenic diet. Rev Neurol, 2001 Nov 16-30;33(10):909-15.
  22. Musa-Veloso K, Likhodii SS, et al. Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals. Am J Clin Nutr, 2002 Jul;76(1):65-70.
  23. Ornish D. Low-carbohydrate diets. Ann Intern Med, 2004 Nov 2;141(9):738-9.
  24. Zhao Q, Stafstrom CE, et al. Detrimental effects of the ketogenic diet on cognitive function in rats. Pediatr Res, 2004 Mar;55(3):498-506.
  25. McGhee B, Katyal N. Avoid unnecessary drug-related carbohydrates for patients consuming the ketogenic diet. J Am Diet Assoc, 2001 Jan;101(1):87-101.