Since everyone is still arguing about how our bodies are Burning Calories… Here is some science.

As the 1970’s unfolded, it was still commonly thought that carbohydrates (in the form of blood glucose and its tissue storage form, glycogen) were the preferred energy sources for working muscles in man. I say commonly thought because evidence had already accumulated that this idea was unfounded, but this fact wasn’t common knowledge during these years, or even today.

In studies of dogs (early 1960’s), glucose from the blood accounted for 10-15% of total energy expended ( ya dogs are Burning Calories ) during prolonged strenuous exercise while fat supplied 70-90% of the total energy required, a finding that made it very difficult for scientists to hold onto their belief that carbohydrates supplied 100% of the fuel needs of working muscles. This was a true, if minor, belief shift, yet it, alone, wasn’t powerful enough to lead to a full-fledged scientific revolution.

Although fat supplied a significant amount of energy to support exercise, the finding that fat from the blood was only a limited portion of the total fat used led to an intensified effort to discover the source of the additional fat fuel that powered muscle contraction.

The fact that fat supplied 70-90% of the total fuel burned wasn’t in doubt. During these years, however, there was no technology capable of determining the source of the fat that “burned”: whether it was from the blood or from inside the muscle. The studies and the technology needed to make these assessments didn’t become a fact of scientific research until after 1995. I’ll discuss this shortly.

One of the first attempts to acclimate dogs to a high-fat diet was conducted in 1977. The outcome of the experiment was that the dogs’ endurance performance increased as the carbohydrates in their diet decreased. Importantly, the lowest carbohydrate intake, zero, led to the best endurance performance.

The authors concluded from their dog experiments that, if humans wanted to test the endurance benefits of a low-carbohydrate diet, they should spend at least twenty weeks accommodating themselves to the high-fat diet. Previous studies in humans consuming a diet restricted in carbohydrate had shown a significant decrease in performance.

These dog studies showed the opposite effect, and the authors suggested that one reason for this effect was the amount of time allotted for the dogs to adapt to this dramatic change in dietary fuels. This 1977 paper was the first scientific publication that brought up the idea that the time allowed for dietary accommodation might be an important variable in the ability of an organism to use different fuels.

Vilhamar Stefansson had suggested this same idea in his 1960 book, The Fat of the Land, which, of course, wasn’t really “acceptable” to science as a “scientific” publication.

The complete understanding of this idea is most important as we begin to develop the idea that the low-carbohydrate diet is the primary asset when it comes to your body body Burning Calories, a road to better health, weight control, and disease protection by eliminating glycation.

In 1983, Dr. Steven Phinney and his coworkers were the next scientists to note that most dietary studies hadn’t afforded enough time for adaptation. Very low-carbohydrate diets are difficult to tolerate in their early stages, with nausea and weakness being the most common side effects. Indeed, these symptoms often contribute to an early end of the dietary experiment.

Interestingly, the authors pointed out that the only existing published studies of people consuming extremely low-carbohydrate diets were those of the Arctic explorers described earlier by Stefansson.

Other empirical evidence observed that North American native people had lived healthy lives on a restricted carbohydrate intake. This fact indicated that humans had the ability to maintain health and to function effectively even during prolonged nutritional ketosis (see the explanation of ketosis three paragraphs below).

From all this, we can readily see just how recent all of these ideas are and why we’re just now experiencing a transition into a new belief system, one whose architect is the citizenry, not our scientific, medical, or government leaders.

The Phinney study used a diet that contained 83-85% of total calories as fat, containing less than twenty grams of carbohydrate a day. Although these lean subjects adapted to and tolerated the diet well, the authors concluded that fuel use and hormonal responses were still incomplete after four weeks of adaptation.

In a follow-up study, these researchers showed that lean, healthy, aerobically trained cyclists could maintain exercise performance after four weeks on a ketogenic diet, an inference drawn from experiments in which those on the ketogenic diet were pitted against cyclists consuming a high-carbohydrate diet.

Ketones form when fat, from fat tissue, reaches high levels in the blood and the liver converts this fat into ketones, secreting them into the blood for transport to the tissues and cells of the body as a source of fat fuel. During starvation, for example, after twelve days, ketones supply more than 75% of the brain’s fuel. They also become the primary fuel for the rest of the body.

Physiological ketosis (ketosis in a healthy person), as opposed to pathological ketosis (ketosis in an unhealthy person), isn’t dangerous as so many believe.

The major difference between cycling performance on the high-fat diet, opposed to the high-carbohydrate diet, was the large increase in ketones experienced by the cyclists on the high-fat diet. 

Interestingly, the use of muscle glycogen decreased by 79% after four weeks of adaptation to the ketogenic diet. Researchers were left wondering about the mechanisms involved in the slowing down of muscle glycogen use. The biochemical pathways and mechanisms involved in the control of fuel use were just beginning to be researched during the early 1980’s.

Unbelievably, the authors concluded that the results of their study did not contradict the then-current understanding that exhaustion correlates with muscle glycogen depletion, which is a part of the intellectual dogma that has held us captive during the era of the woeful glucose-loving belief system.

A 1984 study provided yet-another glitch to the current glucose belief system and one of its sub-beliefs, glycogen loading. These authors first restated the fashionable belief that the amount of glycogen stored in working muscles was the limiting factor in prolonged exercise. Since some subsequent papers suggested that this theory might be incorrect, these researchers saw fit to study further the concept of carbohydrate (glycogen)-loading.

Male rats were divided into four groups: two groups consumed 78% of their calories as fat, and the other two groups consumed 69% of their calories as carbohydrate. The animals were tested at either one or five weeks after beginning the experimental diet, with some animals sacrificed in a rested condition and others sacrificed after an exhaustive treadmill run.

After one week on the low-carbohydrate diet, animals fed fat ran 8% longer than high-carbohydrate-fed animals before becoming exhausted. With continuation of the diet for another four weeks, the low-carbohydrate-fed animals ran 33% longer than the high-carbohydrate-fed animals.

Exhaustion occurred at approximately forty minutes, indicating that the intensity of exercise was heavy, the sort of exercise whose demands, according to the theories of the moment, could not be met by fat.

Clearly, rats adapt to this diet more rapidly than dogs or humans, proved by the fact that, after only one week, performance was already improved.

On average, muscle glycogen content decreased approximately 20% and liver glycogen decreased by 50% at week one and 38% at week five in high-fat animals, suggesting that liver glycogen was rebounding, even though very little carbohydrate was available in the diet.

Finally, we had scientific proof that the well-known notion that a short-term low-carbohydrate diet of three-seven days reduces endurance time is a fact, but not one whose application is broad: It’s a fact for only the first week of its use. Thereafter, metabolic adaptations occur in the muscle, and these adaptations allow the muscle to perform much better on a high-fat diet.

This study also proved that a reduction in the glycogen content of muscle and liver doesn’t limit performance. Importantly, it must be understood that fuel use in muscles is controlled by the enzymes found in muscle.

The available fuel and the hormonal response to it influence changes at the enzymatic level but the mechanism of action is dictated solely by enzymes. In this study, researchers investigated the changes in some of the primary enzymes involved in fat use. The total activity of two critical fat-burning enzymes increased by 77% and 98% respectively; these enzymatic changes dictate an increase in fat burning.

Researchers concluded that untrained rats, which by definition weren’t fat-adapted from training but from diet only, could — through dietary manipulation alone — improve their performance dramatically in prolonged and intense exercise, and all this despite a profound limited glycogen content.

Burning Calories

One of the principal researchers from this study published a review article in 1987, discussing what we knew then about muscle glycogen and performance. Because this scientist was instrumental in uncovering one of the major glitches facing the existing belief-in-carbohydrate-as-primary-fuel, one might hope that he’d expanded and enriched his once-limited vision as a function of his very own, quite formidable, research. But, beliefs don’t give up the ghost easily, however utterly disproved they become. Dr. R. Conlee observed, then, as recently as 1987:

All of these facts indicate that, in spite of the opinion among the scientific community regarding the limitations of fat as an energy substrate, there may be experimental conditions not yet designed under which the disadvantages of fat and, conversely, the advantages of carbohydrate for energy production may not be as polarized as the present literature leads us to believe.

Holding true, however, to the scientific community of which he’s a member, Dr. Conlee observes further:

Such a statement does not imply that man should live on a high-fat diet. That recommendation would ignore the obvious implications for cardiovascular health.

Obvious? As I’ve stated, the belief that fat is implicated in heart disease has been one of the main limitations to understanding and accepting the optimal diet for human health. In fact, with the 1987 introduction by Dr. Anthony Cerami of the glycation theory of aging and disease, it’s becoming ever-more clear that glucose, not fat, as we’ve learned, is the real contributor to the present-day rise in cardiovascular disease.

In 1991, a group of researchers finally got around to setting up an experimental condition that duplicated the experiences of early humans as described by Stefansson some sixty years earlier. At last, science was beginning to catch up with what men had known for thousands of years.

Unfortunately, for one hundred years, we’ve allowed nutritional theories to guide us rather than the centuries, nay eons, of actual human experience.

Citing the study above by Phinney, a group of French researchers fed one group of male rats a 0%-carbohydrate diet and another group a 62%-carbohydrate diet, rounding out their experimental design with an exercise regimen for the animals.

The rats were trained until the scientists were sure that they could maintain one hour of exercise at 80% of their maximal capacity. Most important, the rats were allowed an adaptation period of twelve weeks for both their training and their dietary regimens.

The low-carbohydrate diet group ran for sixty eight minutes before experiencing exhaustion, whereas the high-carbohydrate diet group experienced exhaustion in only forty two minutes. At the end of a five-hour run, only 75% of the carbohydrate-fed animals were still running, but 83% of the rats fed the high-fat diet were still running at the end of the five-hour mark.

After accomplishing the goal of running for five-hours, the rats were encouraged to continue running until exhausted. All of the carbohydrate-fed animals were exhausted within seven hours, whereas six high-fat-fed rats actually had to be stopped at seven and a half hours. They simply hadn’t become fatigued.

My trained, estrogen-treated rats (estrogen treatment allows more fat use), during the time of my Ph. D. research also didn’t tire out; we had to remove them from the treadmill after eight hours because we’d become exhausted just from watching them run!

Confirming the earlier work by Miller, the enzymes involved in burning fat increased. Critical to enzyme action, however, is that the fuel that enzymes act upon must be available. This was accomplished in several ways in this experiment. One is obvious: fat availability increased because the animals ate so much more fat.

The second is less obvious: fat from the body’s fat reserves becomes much more accessible when one consumes a low-carbohydrate diet. Later, I’ll flesh-out the internal environmental conditions in which stored body fat is made available.

In the Simi study above, both diet-induced fat-adaptations and training-induced fat-adaptations were cumulative.

Burning some Calories baby!

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