Ketone bodies are short-chain fats that are produced in the liver to be used for energy. There are three types of ketone bodies: beta-hydroxybutyrate (BHB), acetoacetate, and acetone.
Any diet that encourages the production of ketone bodies by your liver is a ketogenic diet. These diets are high in fat, adequate in protein, and low in net carbohydrates.
Numerous studies are examining a ketogenic diet's effect on fat loss, epilepsy, diabetes, Alzheimer's, heart disease, and cancer.
Ketone bodies are produced in the liver. From the liver, they are transported to other tissues, where acetoacetate and beta-hydroxybutyrate (BHB) can be reconverted to acetyl-CoA (acetone) to produce energy via the citric acid cycle.
Studies have demonstrated ketone bodies to be anti-inflammatory, cytotoxic, neuroprotective, as well as enablers of greater performance in cognition and endurance athletics. Additionally, there are a number of studies that have suggested that ketone bodies can help mitigate migraines, reduce incidences of seizures, stabilize mood in people with bipolar disorder, and aid individuals suffering from traumatic brain injuries (TBI).
Ketogenic foods are higher in fat, adequate in protein, and low in net carbohydrate. Over time, consuming foods with this type of macronutrient distribution will cause the body to switch from a carbohydrate-burning mode to a fat-burning mode. This change occurs as a result of the low intake of net carbohydrate and all substrates that can be converted into carbohydrate. Sensing low net carbohydrates and plenty of fatty acid reserves, the liver will begin to produce ketone bodies to be used as energy from the available fat.
It is a specific type of ratio that compares the amount of fat to the amount of combined protein and net carbohydrate. Common "keto ratios" are 0.5:1, 1:1, 2:1, 3:1, and 4:1. Table 1 shows various ketogenic ratios and the percentage of calories from from fat vs. protein and combined net carbohydrate.
Table 1: Ketogenic Ratios
The keto ratio is one popular method of nutritional tracking used by the keto community. To illustrate how keto ratios work, let's use the 2:1 ratio as an example. "2:1" means that for every 2 grams of fat, there is 1 gram of combined protein and net carbohydrate. This means that a 2:1 food item with, say, 20 grams of fat would have a combined 10 grams of protein and net carbohydrate. Thus, for a 2:1 food or meal, 82% of the calories come from fat, and the remaining 18% of the calories come from protein and net carbohydrate.
Here is an example of the math behind a 2:1 ketogenic ratio: 2:1 meal at 506 calories: 46 g fat (46 x 9 = 414 calories from fat), 23 g protein and net carbohydrate (23 x 4 = 92 calories from protein and net carbohydrate). 414 + 92 = 506 calories.*Note that net carbohydrate is taken by subtracting sugar alcohols (which have a low effect on glycemic response) and dietary fiber from the total carbohydrate count. So for a food item that has 20 g of total carbohydrate, including 14 g of fiber and 2 g of sugar alcohols, this food has a net carbohydrate total of 4 g.
The simplicity of the keto ratio makes it a popular way for keto eaters to assess how a given food item fits into the context of a ketogenic diet.
It is important to note that there are limitations to using a keto ratio for following a ketogenic diet. The reason is that these keto ratios do not specify a low net carbohydrate amount, which is essential for someone to comply with a ketogenic diet. For example, without putting a cap on net carbohydrates, a meal could have 100 grams of fat, 50 grams of carbohydrate, and 0 grams of protein, and it would be considered a 2:1 meal. However, this type of macronutrient distribution would not be favorable for an individual who is attempting to follow a ketogenic diet.
F-Cal is another way of looking at how a meal or food fits into the paradigm of a ketogenic diet. F-Cal stands for the percentage of total calories from a given food or snack that comes from fat. A 2:1 food or snack has an F-Cal of 82%, meaning that 82% of the total calories from this food comes from fat. Using F-Cal and having a daily net carbohydrate maximum (such as 30 or 50 grams) is popular method for many ketogenic eaters to track their nutritional regimen.
Context and quantity matter significantly. Eating lots of saturated fats in while on a ketogenic diet can have profoundly different effects from eating lots of saturated fat through consuming mass quantities of foods high in saturated fat and carbohydrate (such as ice cream) while eating in a caloric surplus.
Monounsaturated fats are fatty acids that have one double bond in the fatty acid chain with all of the remainder carbon atoms being single-bonded. Foods high in monounsaturated fats include avocados, macadamia nuts, hazelnuts, olive oil, almonds, and most meats, including red meat. Animal fats are mostly monounsaturated fat, and many cuts of meat (including red meat) have more monounsaturated fat than saturated fat content.
Polyunsaturated fats are fatty acids that have more than one double bond in the fatty acid chain, with the remaining carbon atoms being single-bonded. Foods high in polyunsaturated fats include most plant and vegetable oils (including soybean, corn, and sunflower oil) and fatty fish such as trout, herring, mackerel, and salmon.
Saturated fats are fatty acids in which all carbon bonds in the fatty acid chain are single bonds. Foods high in saturated fat include red meat pork, poultry with skin, cream, butter, cheese, full-fat and reduced fat dairy items, lard, tallow, and lamb.
Both monounsaturated and saturated fats are transported to the liver and converted into one of the three ketone bodies: beta-hydroxybutyrate, acetoacetate, and acetone. In particular, short-chain saturated fatty acids, such as C-4 (butyric acid), C-6 (caproic acid), C-8 (caprylic acid), C-10 (capric acid), and C-12 (lauric acid) convert very quickly into ketone bodies once ingested.
Medium-chain triglycerides (MCTs) are fatty acids that have aliphatic tails ranging from 6 to 12 carbon atoms. There are three main types of MCTs: C6 (caproic acid), C8 (caprylic acid), and C10 (capric acid). The number after the C signifies the length of the carbon chain. So, for C6 (caproic acid), this MCT molecule has a carbon atom chain length of 6.
MCTs are an energy source that rapidly convert to usable fuel in the body. When MCTs are ingested, they bypass gastric digestion and are transported to the liver, where they are processed and converted into ketone bodies. This spike in ketone body production can also induce greater mental clarity, as ketone bodies, along with glucose, can cross the blood-brain barrier to be used for fuel.