Over the last few years, it has been increasingly evident that low-carbohydrate diets are more effective for weight loss than low-fat diets. 1,2,3,4 In addition to added weight loss, low-carb diets seem to improve lipid profiles. One study reported that an Atkins-style low-carb ketogenic diet, which included a vitamin and nutritional supplement, caused more weight loss than a low-fat diet. Along with losing an average of 26 pounds, dieters assigned to the low-carb plan lost more body fat and lowered their triglyceride levels and raised their HDL, or good cholesterol, more than the low-fat dieters.The low-fat dieters lost an average of 14 pounds.5 Every bodybuilder I speak to comments that the first week of a low-carb ketogenic diet is the worst— you feel fatigued, and many people just can’t think straight! Is this a coincidence, or is something going on inside your brain/body?
High-Protein/High-Fat Diets Turn On Fat-Burning Genes
Several animal and human studies indicate that dietary fats increase the expression of genes regulating fat metabolism in skeletal muscle. Plasma fatty acids are increased after a short-term, high-fat diet and also increase the expression of several key genes associated with fatty acid metabolism.6 One study investigated low- and high-fat diets and changes in enzymes that control fat metabolism in endurance-trained, men. Irrespective of training, beta-hydroxyacyl-CoA-dehydrogenase activity in the thigh muscle was significantly increased by an average of 25 percent after adaptation to a fat-rich diet, and was unchanged after adaptation to a carbohydrate-rich diet.7 Another study reported that in as little as five days, athletes on a high-fat, high-protein diet— during a 20-minute exercise bout— increased fat oxidation almost twofold over those on a high carb diet; in conjunction, there were significant increases in the fat-oxidation enzymes in skeletal muscle after consuming the high-fat diet.8 In sum, the elevation in free fatty acids causes an increase in uncoupling proteins.
What’s Going On Inside The Brain And Heart?
Uncoupling proteins (UCPs), which are found in muscle and also in adipose tissue, are also found in the brain and heart. I know you are asking, What the hell is an “uncoupling protein?’ Dr. Dan Gwartney offered a good explanation in a previous edition of MD’s Fat Attack. He commented, “Uncoupling is a process that is similar to holding the clutch down in a manual transmission car. When the clutch is pressed (disengaged), the transmission is ‘uncoupled’ from the engine, and the power is not transferred to the wheels. Hence, when the clutch is pressed, the engine turns and does not create movement. If the engine runs, the energy produced is lost as heat. If the gas pedal is pressed, the engine turns faster but no movement occurs as long as the clutch is disengaged; instead, the rate of energy (gasoline) consumed is increased and additional heat is lost.
Get it? In a nutshell, stimulating UCPs stimulate thermogenesis and increase the energy requirements inside the cell.The bodybuilding drug DNP is a potent stimulator of UCPs.The interesting physiological fact is that UCPs are stimulated by elevated free fatty acids, which are abundant while on low-carb diets.The research is clear that longterm, low-carb ketogenic diets have favorable effects on lipids— but the short-term effects on what happens to the brain and heart are less clear.
Sorry For The Bad Interview, Shawn My Brain Ucps Are Being Stimulated!
I have seen it a hundred times—Shawn Ray is interviewing a carb depleted bodybuilder and the guy blanks out and says, “What the hell was the question?”This is no coincidence! Researchers reported in the American Journal of Clinical Nutrition that when healthy young men were placed on a low-carb ketogenic diet that consisted of 70 percent of calories from fat, 4 percent carbohydrates, and 26 percent protein for seven days, there were some interesting physiological findings.The researchers used cardiac magnetic resonance (CMR) spectroscopy and MR imaging, which is a non-invasive way of measuring physiological processes occurring in the heart. They found that after seven days on a low carb diet, high-energy phosphocreatine levels in the heart were decreased in conjunction with impaired cognitive function. Interestingly, when subjects were placed back on a normal diet the effects on the heart and brain were reversed.This may explain some of the physiological effects of low-carb diets during the first seven days— however, many people comment that after the first week, the symptoms do get better after the body has adapted to low carbs.
High Free Fatty Acids Stimulate Ucps In The Brain And Heart
After seven days on the low-carb, high fat ketogenic diet, serum free fatty acids increased as expected, with a small reduction in bodyweight. The more concerning finding was the low- carb diet decreased cardiac high-energy phosphate metabolism. Under normal physiologic conditions, FFAs and glucose are major substrates for energy metabolism in the heart—and the relative supply of each alters myocardial oxygen consumption. Cardiac imaging studies have found that increased FFAs available in the plasma parallel increased myocardial FFA oxidation.The oxidation of FFA requires 11 percent more oxygen per carbon unit than oxidation of glucose,9 so there is greater metabolic demand placed on the heart. It was found that the uncoupling protein UCP3 was stimulated in the heart by the increase in free fatty acids. It was previously reported that mitochondrial uncoupling could explain the increased oxygen consumption during enhanced uptake of FFAs in dog hearts.10This could explain the heart’s lower PCr/ATP levels due to the increased expression of uncoupling proteins in the heart, which increased the metabolic substrate use— much like there is a drop in PCr/ATP use in muscle after intense exercise.
Another interesting finding was that cardiac metabolic energy returned to normal when the subjects switched back to a normal diet.The other interesting finding of the study was that the researchers gave subjects on the low carb ketogenic diet a complete barrage of cognitive tests, which showed the subjects were impaired while on the low-carb ketogenic diet.The subjects consuming the low-carb ketogenic diet had a reduction in the ability to concentrate and a reduction in the ability to perform complex working tasks— including focus attention and working memory. The researchers commented that the elevated circulating fatty acids may have caused the same energy deficits in the brain as observed in the heart, via direct changes in metabolism.11The brain is highly dependent on glucose as a substrate for fuel; hence, it is conceivable that the carbohydrate restriction could be responsible for the observed cognitive deficits, especially because the carbohydrate intake was 4 percent with the high-fat diet. It is possible that higher plasma ketones, which can occur with high-fat diets and can be taken up and oxidized by the brain, offset the effect of reduced carbohydrate availability.
A generalized concept of fatty acid-induced cellular impairment could account for the findings with the high-fat diet. In conclusion, the study points out that high free fatty acids cause activation of UCPs— which increase the metabolic demand of cells, including those in the brain and the heart. The study found that after seven days on a low-carb diet, the lean, healthy subjects had a drop in cardiac high-energy metabolites and a reduction in memory and attention.These effects were reversed when the subjects switched back to a normal diet. This may be the reason so many bodybuilders complain that the first week on a low-carb ketogenic diet is like “hell week.” The long-term effects of a low-carb diet are not known, but this short-term study may explain the fatigue and lack of ability to concentrate while on a low-carb diet.
Written By: Robbie Durand, M.A.
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