2011 in depth discussion / lots of good stuff
Steve Phinney and Richard Johnson: Ketones, Uric Acid, High Fat and Health
When they say “muscle breakdown” I’m wondering if they mean through the process of autophagy. I don’t think it’s gluconeogenesis because that doesn’t happen in the muscle and mainly takes place in the liver and kidneys. I just looked this up to confirm and found out this is because muscle cells do not have glucose 6- phosphatase enzyme which is required to convert glucose 6-phosphate to glucose. Glucose 6- phosphatase can only be established in the endoplasmic reticulum of kidney and liver cells.
It seems like muscle break as it correlates to higher uric acid levels is mainly a problem when you are switching from using glucose to using fat, but I’m wondering if it might also be a problem on a low carb or calorie restricted diet if blood sugar and insulin remain high.
Muscle breakdown occurs in a number of different circumstances. First, every protein in the body has a designated lifetime, ranging from minutes to years, and needs to be disassembled at the end of its usefulness. This type of autophagy is ongoing.
Second, damaged proteins need to be dismantled and replaced. This is also an ongoing process.
Third, the body needs nitrogen for certain purposes, and the amino acids from which that nitrogen is freed have to come from somewhere. (Unfortunately, we cannot utilise the nitrogen in the air, only nitrogen that is part of an amino acid.) The body’s ability to store amino acids is limited, so if nitrogen is needed, it can come from muscle tissue, if necessary.
Fourth, while the body doesn’t normally use amino acids as fuel, it can, in fact, do so when necessary, in cases of famine or fasting. Amino acids can be deaminated, converted into glucose or fatty acids, and then metabolised as normal. The extra couple of steps cost ATP, so the body doesn’t normally do this, except when extracting nitrogen or when the liver needs to make glucose. The ATP yield from protein is smaller than from an equivalent amount of glucose or fat.
Fifth, there are processes of damage and repair that occur when we stress our muscles with exercise. As long as we have adequate protein intake, this allows muscles to grow.
Because the body needs to use a certain amount of nitrogen a day, and because its ability to store amino acids is limited, a certain daily intake of protein is essential, if we wish to preserve muscle mass. (There are also certain essential amino acids that must be present in food, since the body cannot convert them from other amino acids.) When there are no amino acids (protein) coming in, the body scavenges them from tissues, first cleaning up damaged and elderly proteins, but then starting in on muscle mass. (Have you seen pictures of newly-liberated concentration camp survivors from World War II? Their bodies had consumed both fat and muscles in an attempt to keep them alive on short rations, leaving them emaciated.)
A low-carbohydrate/ketogenic diet that is adequate in protein and fat will not promote muscle breakdown, since the amino acid and energy intake will be abundant enough to meet the body’s needs. Only the daily minimum of nitrogen loss will occur, and that will be balanced by the protein intake. This is why we recommend eating a good amount of protein and adding enough fat to satisfy one’s hunger.
Why would blood sugar and insulin remain high on a low-carb/ketogenic diet? If you are not supplying energy to your body in the form of glucose (also known as carbohydrate), and you are skimping on calories because of the strong indoctrination to “eat less, move more,” then granted, the liver is going to be making enough glucose to feed your body, in an attempt to get you through the famine. But people eating a well-formulated ketogenic diet to satiety are getting enough energy (in the form of fat), and their insulin will be low because of the lack of glucose/carbohydrate coming in, so that is not likely to be a problem.
I guess the key is, as you said, a “well-formulated” ketogenic diet. In that case this shouldn’t happen, but sometimes, I think it’s harder said than done!
Real, whole foods are the key. Processed foods and sugary drinks are the enemy, even on a high-carb diet.