The glycogen in our muscles and liver will run out. Once we have been in a fasting state for longer than 24 hours, we transition into a starved state. More fatty acids from stored fat enter the circulation, and more ketones are produced the longer we stay in a fasted state. The liver will also form ketones from these fatty acids, which our brain uses for fuel when blood sugar isn’t available in abundance (our brain cells don’t use fatty acids for fuel). These are the primary fuel source for the liver and muscles while we are sleeping or doing low-intensity exercise like walking. In turn, this glucose is primarily used by the brain and red blood cells.įree fatty acids are released from the fat cells that are in the form of triglycerides. When liver glycogen is released, glucose levels increase in the bloodstream. Each one is converted into acetyl-CoA, which is an important part of creating ATP (our primary energy shuttling molecule) in the Kreb’s Cycle. In a fasting state, our stored energy sources, such as glycogen, fat, and muscle, are broken down by different processes and metabolized into the same fuel. With this drop in blood glucose, insulin’s opposing hormone, glucagon, will be secreted, triggering the release of stored fuel from glycogen and fat cells. The fasting state occurs when our blood glucose is at a borderline level, which also means our insulin levels are decreased. This helps shuttle the glucose into our cells to be used as energy or stored as glycogen or fat for future use. When our glucose levels increase, the pancreas secretes insulin into the blood. Most of the carbohydrates we consume are broken down into glucose which is used as an immediate energy source.If we have any extra amino acids, they circulate and repair tissue or get converted into glucose and stored as glycogen (our storage form of glucose). Proteins are processed into amino acids through a process called transamination and sent off to create neurotransmitters, enzymes, non-essential amino acids, and other protein-based compounds.Excess fats are stored as triglycerides in the fat cells throughout the body. Once they enter our circulation, the fats are sent around the body to provide fuel for our heart and other tissues, repair cells, and make different chemicals, hormones, and tissues in the body. The fats we eat, except for medium-chain triglycerides, enter the bloodstream through the lymphatic system.In the fed state (i.e., after we eat a complete meal), the macronutrients we consume are broken down through separate metabolic pathways: Starved – When haven’t eaten in more than 24 hours.Fasting – When we haven’t eaten in 2-8 hours.These “states” can be broken down into three main categories:

So, what exactly do I mean by metabolic pathways? Put simply, they are the mechanisms by which the body digests and uses fats, proteins, and carbohydrates depending on its current “state.” However, the most important thing to understand is how these nutrients are being utilized for energy via our metabolic pathways. Carbohydrates are, of course, 100% anti-ketogenic, as they raise both blood glucose and insulin – two key factors that trigger a decrease in ketone production.īecause of their anti-ketogenic activity, protein and carbohydrates will impact our ketone levels and make it harder for us to transition into ketosis.Insulin indirectly decreases ketone production. Proteins are roughly ~46% ketogenic and 58% anti-ketogenic since insulin levels usually rise in response to the absorption of specific amino acids.Fats are 90% ketogenic and 10% anti-ketogenic, due to the small amount of glucose that is released in the conversion of triglycerides into usable energy.All three of these nutrients have different effects on ketosis because of how our body digests and metabolizes them.

The three main macronutrients that are relatable to a keto diet are fats, proteins, and carbohydrates.

Macros for keto diet