The primary goal of our metabolic system is to provide fuels in the amounts needed to maintain optimal functioning and ageing of our various biological systems. There is a resurgence of interest in low carbohydrate nutritional intake and lifestyle adaptation due to failure of the world with low-fat diets to control the pandemic of obesity (BMI > 30), overweight (BMI > 25) and the Metabolic Syndrome (low HDL; elevated triglycerides; Insulin Resistance with elevated Glucose; visceral adiposity and above optimal BP). Based on studies of the Paleolithic diets (primitive man), that starvation and carbohydrates restriction are simply the polar ends of a continuum, and that carbohydrate restriction was the norm for most of our existence as upright walking beings on this planet, making the metabolism of what biochemistry textbook authors call starvation the ‘normal’ metabolism.
During starvation the primary goal of the metabolic system is to provide enough glucose (our usual fuel 100% of the time) to the brain and other tissues (the red blood cells, vascular endothelium, certain kidney cells, and others) that absolutely require glucose to function. Which makes sense if you think about it. You’re a Paleolithic man or woman, you’re starving, you’ve got to find food, you need a brain, red blood cells, etc. to do it. You’ve got to be alert, quick on your feet, and not focused on how hungry you are. If you’re not eating or if you’re on a low-carbohydrate diet, where does this glucose come from? If you’re starving, glucose comes mainly from one place, and that is from the body’s protein reservoir: muscle. A little can come from stored fat, but not from the fatty acids themselves. Although glucose can be converted to fat, the reaction can’t go the other way. Fat is stored as a triglyceride, which is three fatty acids hooked on to a glycerol molecule. The glycerol molecule is a three-carbon structure that, when freed from the attached fatty acids, can combine with another glycerol molecule to make glucose. Thus a starving person can get a little glucose from the fat that is released from the fat cells, but not nearly enough. The lion’s share has to come from muscle that breaks down into amino acids, several of which can be converted by the liver into glucose (via the Cori cycle). But the breakdown of muscle creates another problem, namely, that (in Paleolithic times and before) survival was dependent upon our being able to hunt down other animals and/or forage for plant foods. It makes it tough to do this if a lot of muscle is being converted into glucose and your muscle mass is dwindling.
The metabolic system is then presented with two problems: 1) getting glucose for the glucose-dependent tissues; and 2) maintaining as much muscle mass as possible to allow hunting and foraging to continue. Early on, the metabolic system doesn’t know that the starvation is going to go on for a day or for a week or two weeks. At first it plunders the muscle to get its sugar. Surprising to most, a normal blood sugar represents only about a teaspoon of sugar dissolved in the entire blood volume, so keeping the blood sugar normal for a day or so doesn’t require a whole lot of muscular sacrifice. If we figure that an average person requires about 200 grams of sugar per day to meet all the needs of the glucose-dependent tissues, we’re looking at maybe 150 g of muscle per day, which isn’t a deal over the first few days. But we wouldn’t want it to continue at that rate for prolonged periods. If we could reduce that amount and allow our muscle mass to last as long as possible, it would be a big help.
The metabolic system could solve its problem by a coming up with a way to reduce the glucose-dependent tissues’ need for glucose so that the protein could be spared as long as possible. Ketones to the rescue. The liver requires energy to convert the protein to glucose. This energy comes from fat. As the liver breaks down the fat to release its energy to power glucose production (gluconeogenesis), via the conversion of protein to sugar, it produces ketones as a by-product of the beta oxidation of fat. And what a by-product they are. Ketones are basically water-soluble (meaning they dissolve in blood) fats that are a source of energy for many tissues including the muscles, 80% of brain and heart. In fact, ketones act as a stand in for sugar in the brain only when glucose is not available. Although ketones can’t totally replace all the sugar required by the brain, they can replace a pretty good chunk of it. By reducing the body’s need for sugar, less protein conversion to glucose is required, allowing the muscle mass (the protein reservoir) to last a lot longer before it is depleted. And ketones are the preferred fuel for the heart, making that organ operate at about 30 percent greater efficiency. Fat is the perfect fuel as we literally have a ‘ton’ of it stored compared to our Glycogen stores (our stored Glucose). Fat provides energy to the liver so that the liver can convert protein to glucose. The unusable part of the fat then converts to ketones, which reduce the need for glucose and spare the muscle in the process.
If, instead of starving, you’re following a low-carbohydrate diet, it gets even better. The protein you eat is converted to glucose instead of the protein in your muscles. If you keep the carbohydrates low enough so that the liver still has to make some sugar, then you will be in fat-burning mode while maintaining your muscle mass, the best of all worlds. How low is low enough? Well, when the ketosis process is humming along nicely and the brain and other tissues have converted to ketones for fuel, the requirement for glucose drops to about 120-130 gm per day. If you keep your carbs below that at, say, 60 grams per day, your liver will have to produce at least 60-70 grams of glucose to make up the deficit, so you will generate ketones that entire time.
THE KETONE GENERATING (KETOGENIC) DIET AND LIFESTYLE:
A Ketogenic Diet is a muscle-sparing fat-loss diet that works by forcing the body into ketosis through carbohydrate deprivation. As indicated above Ketosis is a state where the body converts fat into ketones that the brain and other metabolically active organs can use for fuel when glucose (carbohydrates) are in short supply. It’s metabolic trickery that has some major advantages over a regular, carbohydrate based diets. The only time the body would create and utilise ketones as our fuel in large quantities is when insufficient glucose is available as a fuel source. The way to make glucose unavailable, is to simply restrict total carbohydrate consumption to 30-60 g/day or less. For example, if you stop eating all carbohydrates at, say, 6:00 PM on Sunday, and then do a heavy exercise workout Monday and Tuesday, this will deplete your liver and bloodstream of glucose, and your muscles of glycogen (storage glucose). At that point, your liver will start producing ketones, so the brain has a fuel to work with, and if you consume no carbohydrates at all, the body will start converting protein into glucose as it will still needs at least 200 g glucose per day for all the glucose dependent tissues.
There are many benefits of keto-dieting, among them are: Your body burns fat as its primary fuel source 24 hours a day, 7 days a week. Thus, if you restrict calories as well as carbohydrates, you will burn off adipose body fat at a rate no carb-based diet can match. Next, people in ketosis very often eat much less than when they’re on carbs as ketosis strongly blunts hunger, which makes it much easier to restrict calories. Keto-diets also naturally spare lean muscle mass, far more than normal diets, when adequate protein is consumed (50-150 g/day minimum, usually one and half g/kg bodyweight recommended). Sparing lean muscle mass is incredibly important to maintain muscle mass, energy and strength, as it helps to keep your metabolism from slowing down, which helps both in keeping the fat loss going, and with maintaining the fat loss once you’re off the diet. Maintaining muscle mass and integrity is also critical for daily exercise paramount to keep the body in ketosis.
Keto-dieting does have its disadvantages though. Many people think that keto-dieting is very unhealthy due to the high amount of fat and cholesterol that you can consume on the diet (relative to ‘normal’ diets). But, if you make wise food choices, you can stay on a keto-diet while eating very healthy. (See details on Eco-Atkins diet below). Another disadvantage is that it’s very restrictive in the fact that carbohydrates are in most foods people eat on a day-to-day basis, and this can make keto-dieting tough at first. Next, when exercising, at first over week one to three you will be fatigued, because your muscles will still use glucose to produce the energy needed for exercise until you are fully ‘keto adapted’. This can be a bit depressing, but the strength is easily regained when keto adaptation occurs and your body has fully converted to ketones as fuel. One last problem can be bad breath, one of the ketones your body produces is Acetone, which can be deteced in your breath. This can produce ‘fruity’ and not-great smelling breath in some people but with extra care with oral hygiene and high water intake this is not a problem.
As for the details of the ketogenic diet, the rules are minimal carbs, 30-60 grams per day or less. Now, even though you’ll eat very few carbs, you still need close to your normal amount of calories per day (depending on your personal maintenance level of calories, let’s use a 72 kg male at 2500 cals/day as an example). To get that many calories from protein, you would need to eat 625 grams of protein per day, and the body simply cannot handle that much protein as it is too toxic to the liver and kidneys. An excellent level of protein is about 1 1/2 gram per kg of bodyweight. For our example would be only 175 grams of protein per day, or 700 calories! If your calorie intake is that low, your metabolism WILL start slowing down, and fat loss will stop. I recommend going no lower than 500-1000 calories below maintenance level. So if we had this 72 kg man at 2500 cals /day maintenance level, 1500-2000 calories would be the lowest he could go, so the rest of his calories must come from fat, or a full 800-1300 calories.
This allows some variation in keto diets. Taking high animal (saturated) fat for the calories from bacon, biltong, dry wors, cheese, yoghurt, hamburgers, steak, ham, whole eggs and chicken, has the negative of high cholesterol and saturated fat intake. The other option is to get the fat calories from vegan and oily fish origin. This would include olives, extra virgin olive oil, avocados, nuts and seeds particularly raw oily Macadamia nuts. I personally favour a combination of fish, vegan, salad, nuts and seeds as this fat intake is low cholesterol, low in saturated fat and high in mono and polyunsaturated fat specifically omega 3 fats together with some red meat in the form of lean steak. This modification takes care of fibre intake and counteracts constipation.
The keto diet with more vegan and nut/seed intake is referred to as the Eco-Atkins diet. Ideally if you decide you will take 2500 calories daily, 60% of the calories must come from fat, 30% from protein and 10% or less of the calories from carbohydrates. Despite the necessarily higher intake of saturate fats and cholesterol we actually see a REDUCTION in overall cholesterol levels, and improved LDL/HDL ratios (bad/good ratios). I recommend having your cholesterol checked both before the diet, and after 8 weeks on the keto diet. Side effects of the diet include: intermittent fruity breath due to acetone respiration. Feeling nauseous during the first few weeks of keto adaptation is common when you switch over from glucose to ketones as your fuel. The solution to this is to add a few carbs back in each day, say an extra 10-15 grams or so. In the first week you may also feel a little ‘cloudy’, but after that your brain will get used to it. What happens is that the first time you keto diet, your brain can still only use 100% glucose for fuel, so the liver creates the glucose from protein using a process called gluconeogenesis. After three weeks in ketosis, the brain can get up to 70-75% of it’s fuel from ketones, which is when you really start feeling ‘normal’ again. In fact with the greater supply of ketones for energy you will be surprised how energised you feel and how improved athletic performance may be once fully keto-adapted.