Diet and Metabolism

by Rich Amber

The Science Explanation (jump down a couple pages if this is too heavy)

All living things must have an unceasing supply of energy and matter. The transformation of this energy and matter within the body is called metabolism (from µetaß???sµ?? (“metabolismos”), the Greek word for “change,” or “overthrow” (Etymonline)). Metabolism is the biochemical modification of chemical compounds in living organisms and cells (your chemical processes). This includes the biosynthesis of complex organic molecules (anabolism or constructive metabolism, where small precursor molecules are assembled into larger organic molecules. This always requires the input of energy, often as Adenosine Triphosphate – ATP) and their breakdown (catabolism, or destructive metabolism, where larger organic molecules are broken down into smaller constituents. This usually occurs with the release of energy (usually as ATP)). Metabolism usually consists of sequences of enzymatic steps, also called metabolic pathways.

Total metabolism is all of the biochemical processes of an organism. Cell metabolism includes all chemical processes in a single cell. The study of total metabolism is called metabolomics.

The halt of metabolism in a living organism is usually defined as its death. Some organisms can reduce their metabolism to almost zero for certain periods of time. Spores of fungi can survive thousands of years in that state (for those of you with a UFO bent, J this means that it is entirely possible that the first fungus on Earth came from elsewhere – this organsim can travel in deep space in its “sleeping” state, yet still wreak havoc when “awakened” in our atmosphere). But every lifeform is bound to have metabolism at some point of its life cycle, with the possible exception of viruses, which use their hosts’ metabolism.

Human cells obtain most of their energy from chemical reactions involving oxygen. A starting point in measuring human metabolism is with the basal metabolic rate. Some microbes even metabolise the wrought iron on shipwrecks, forming structures known as rusticles with the waste compounds they produce.

All animals, including us, are heterotrophs. We secure all our energy from organic molecules taken in from our surroundings (food). Although heterotrophs might feed partially (as most of us do) or exclusively on other heterotrophs, all the food molecules come ultimately from autotrophs. We may eat beef but the steer ate grass (grass being an autotroph that uses the energy of sunlight to assemble inorganic precursors, chiefly carbon dioxide and water, into the array of organic macromolecules of which they are made. The process is photosynthesis. Photosynthesis makes the ATP needed for the anabolic reactions in the cell.).

Heterotrophs degrade some of the organic molecules they take in (catabolism) to make the ATP that they need to synthesize the others into the macromolecules of which they are made (anabolism).

We are totally dependent on ingested preformed organic molecules to meet all our energy needs. We are also dependent on preformed organic molecules as the building blocks to meet our anabolic needs, which should lead us to a discussion of human nutrition (more in a later issue).

The steps are: 1) Ingestion: taking food within the body, 2) Digestion: the enzyme-catalyzed hydrolysis of polysaccharides (e.g., starch, carbs) to sugars, proteins to amino acids, fats to fatty acids and glycerol, and nucleic acids to nucleotides. 3) Absorption into the body and transport to the cells, which leads us back to the anatomy lesson in newsletters 4-5, and 4) Absorption into cells.

Within the cells, these molecules are further degraded into still simpler molecules containing two to four carbon atoms. These fragments (e.g., acetyl-CoA) face one of two alternatives: They may proceed up various metabolic pathways and serve as the building blocks of, for example, sugars and fatty acids. From these will be assembled the macromolecules of the cell: polysaccharides, fats, proteins, and nucleic acids. Or the molecules in this pool of two-to-four-carbon fragments might be still further degraded – ultimately to simple inorganic molecules such as carbon dioxide (CO₂), water (H₂O), and ammonia (NH₃).

Getting Fat from Eating Too Many Sweets

The immediate source of energy for most cells is glucose. Our bodies extract energy from glucose (we could go into Glycolysis and Cellular Respiration but you don’t want to read 40 volumes to get the point – I’ll touch briefly on this in a later newsletter).

Glucose is not the only fuel that cells depend on. Others include carbohydrates, fats, and even proteins, which may, in certain cells or at certain times, be used as a source of ATP.

The complexity of the mechanism by which cells use glucose might make you fervently hope that a similarly-constructed system is not needed for each kind of fuel. Luckily, it is not.

One of the great advantages of the step-by-step oxidation of glucose into CO₂ and H₂O is that several of the intermediate compounds formed in the process link glucose metabolism to the metabolism of other food molecules.

For example, when fats are used as fuel, the glycerol portion of the molecule is converted into PGAL (phosphoglyceraldehyde) and enters the glycolytic pathway at that point. Fatty acids are converted into molecules of acetyl-CoA and enter the respiratory pathway to be oxidized in the mitochondria.

The amino acids liberated by the hydrolysis of proteins can also serve as fuel. First, the nitrogen is removed, a process called deamination, then the remaining fragments enter the respiratory pathway at several points. For examples, the amino acids Gly, Ser, Ala, and Cys are converted into pyruvic acid and enter the mitochondria to be respired. Acetyl-CoA and several intermediates in the citric acid cycle serve as entry points for other amino acid fragments.

These links thus permit the respiration of excess fats and proteins in the diet. No special mechanism of cellular respiration is needed by those animals that depend largely on ingested fats (e.g., many birds) or proteins (e.g., carnivores) for their energy supply.

Much of the protein we consume is ultimately converted into glucose (a process called gluconeogenesis) to provide fuel for the brain and other tissues.

Although all our foods are inter-convertible to some extent, they are not completely so. In other words, no single food can supply all our anabolic needs.

We can indeed synthesize many fats from glucose, but certain unsaturated fats cannot be synthesized and must be taken in directly in our diet. These are: linoleic acid, linolenic acid, and arachidonic acid. All are unsaturated; that is, they have double bonds.

Although we can synthesize 11 of the amino acids from carbohydrate precursors, we must obtain nine others (the “essential amino acids”) directly.

Many of the points that connect carbohydrate metabolism to the catabolism of fats and proteins serve as two-way valves. They provide points of entry not only for the catabolism (cellular respiration) of fatty acids, glycerol, and amino acids, but for their synthesis (anabolism) as well. Thus the catabolic breakdown of starches can lead (through acetyl-CoA and PGAL) to the synthesis of fat (as so many of us know!).

Plain Language Version

It doesn’t matter whether you are male or female, low calorie dieting slows your metabolism, making it progressively more difficult to lose weight and keep it off. The failure rate of most diets is astronomical, yet people continue to try one after another, always hoping that each new scheme will provide the solution. If you’re a veteran of the diet wars, the one word answer to your dilemma should be muscle. Let’s take a look at why diets often fail and how strength training (exercise) can rev up your metabolism.

Dieting fails due to a combination of hormonal changes, muscle loss, and flat out frustration. When faced with a shortage of calories, your body’s natural response is to conserve fat. This mechanism might have come in handy for our distant ancestors trying to survive a famine, but the “starvation response” and it’s associated hormonal changes make life difficult for many a dieter.

If a dieter persists long enough with the self-imposed famine, the body begins to break down muscle tissue for fuel. When that protein is broken down, it releases nitrogen. Your body will quickly wash away the nitrogen by releasing water from tissue cells, causing an immediate reduction in water weight and a noticeable drop on the scale. However, water and muscle loss is nothing to celebrate. The water weight will be quickly regained as soon as you have something to drink, and the missing muscle can wreak havoc on your metabolism for a good long time.

Muscle is a metabolically active tissue. It requires a certain number of calories each day to maintain itself. Therefore, the more muscle you have, the more calories you burn even when you’re just sitting around. As your muscle mass drops, so does your daily calorie requirement. Suppose, for example, that a dieter loses 10 pounds of muscle (along with maybe 20 lbs. of fat) on a strict diet. Now suppose that each pound of muscle had been burning 50 calories a day just sitting there. Together, those 10 pounds of muscle had been burning 500 calories a day. With this muscle tissue gone, the dieter must now consume 500 fewer calories a day in order to maintain that weight-loss.

However, we know that most dieters won’t keep up the starvation routine for long. They’ll eventually return to their old eating habits. When this happens, the weight inevitably comes piling back on. The kicker is that while they lost both muscle and fat during the diet, what they put back was all fat. So, even though they might weigh the same as they did when they started, they now have a lot more fat and a lot less muscle than they did before the diet. This means that their metabolisms are slower and their calorie requirements are lower. Even if they return to their pre-diet eating habits, they still require 500 fewer calories a day due to the muscle loss. That’s one reason dieters are prone to regaining all of the lost weight and then some.

The solution to this dilemma is an active lifestyle that includes aerobic exercise, a weight-training program (pushing that lawnmower or digging that garden works as well as those bowflex machines), and a healthy diet (Le Anne just explained that – see more below). A healthy diet keeps your metabolism in high gear with 4 to 6 small meals a day (who was it that dictated we must eat exactly three meals?). No food (as long as it isn’t full of mycotoxins) is truly off-limits, but sweets and high-fat junk food should be eaten less often and in smaller quantities. A healthy diet is realistic and permanent; not something you suffer through for a week or two and then quit.

The goal is to consume as many calories as you can while still losing body fat and maintaining or gaining lean muscle. If your calories are already below normal, don’t restrict them further. Instead, stick with your current amount and focus on becoming stronger and more active, so you can gradually increase your calories to a normal healthy level. If your calorie intake is already in a healthy range, decrease it only slightly, and only if necessary. A small reduction of about 250 calories a day, or 10-15 percent less than usual, is more likely to protect your lean muscle and less likely to trigger a slow-down in your metabolism.

Following this type of routine, it’s possible to gain about one pound of muscle per week and lose about one pound of fat per week. The end result is that the number on the scale might not move much at all, but your clothes will get loser and your self-esteem will sky-rocket. It’s at this point that a lot of people will chuck the weight training because they don’t understand the physiology of what’s happening.

The truth is that when you’re strength training, it’s possible to get smaller and heavier at the same time. Muscle is a much denser tissue than fat. A pound of muscle is like a little chunk of gold, while a pound of fat is like a big fluffy bunch of feathers. The fat takes up more space on your body. At this point, it’s best to toss out the bathroom scale and rely on the way you look and the way your clothes fit. The scale can be misleading and discourage you when you’re actually doing great.

The bottom line is that you want to make strong, healthy, positive changes rather than punishing your body and your spirit with starvation. Your goal is the sleek healthy body of a naturally lean person who can enjoy what they eat. You want to avoid, at all costs, the frail sagging body of a chronic dieter who has to measure every morsel.

Le Anne Adds…

You don’t have to cut calories, just change the foods you’re eating. That’s what I’ve been doing. Obviously, since the carbs (grains) contain mycotoxins, I’m trying not to eat as many as those. One of the results of that has been that I’ve been tired. The mycotoxin-free diet is very restrictive and shouldn’t be used by children, pregnant or nursing women, or very active people. It’s also only for short-term use, not forever (the mycotoxin-free diet, not the general dieting idea). Because I do so much physical labor, I simply needed to have more carbohydrates, so I eat rice instead of pasta, potatoes, or corn. Rice is lower in mycotoxins (a little bit, anyway) than other grains, and so that’s what I’ve been choosing to eat. Along with fish, chicken, turkey, cheese, nuts (not peanuts!), eggs, and lots of veggies, especially carrots, which are antifungal. There’s no reason this has to be a strict “low-calorie” diet.

What Rich was saying about low calories is that to lose weight, you have to burn more calories than you take in beyond your maintenance level. That’s simple math. But you can still rid your body of a systemic fungal infection without losing weight, if you so choose. Just eat more of the “good” foods to reach a calorie intake that you’re comfortable with.

With a low-mycotoxin diet, there’s also the die-off to consider. When you start starving out the fungi in your system, they put up a fight at first, demanding that you feed them. This is why most “diets” fail – people get irresistible cravings and fall off their diet for a day or a week or forever. But if you don’t feed those fungi, they die and end up in the liver for processing and excretion. This is called the “Herxheimer Reaction,” and it can cause feelings of fatigue, bloating, and general ill feeling. The more severe your fungal infection is, the more you’ll notice the die-off reaction. It only lasts for a short time (hang in there), but after you’ve gotten rid of the fungi, you must replace your good gut flora or you’re still leaving the playing field open for a new invasion of fungi, some of which you can get just by breathing damp, humid air. It’s an ongoing battle, until you can build up your body’s own immune system and beneficial bacteria to the point where they can handle what little you expose yourself to. This means you can’t just go back on corn and peanuts and start taking antibiotics again. That’s going to undo everything you just achieved.

You need to make a committed lifestyle change to remain healthy.