When using fat for fuel on a ketogenic diet, it is important to choose quality dietary fats. To qualify fatty acids, two structural characteristics are used:
- Length of the carbon chain
- Short (2-3-4) (Dairy fat)
- Medium (6-12) (Tropical oil: Coconut, Palm kernel and MTC oil)
- Long (14 or more) (Olive oil, EPA, DHA etc.)
As a general rule the short and medium lengths are metabolized quickly and easily by the body; they will be diffused from the GI tract to the portal venous system, fed to your good gut bacteria or they will kill bad ones. This is why I use butter and coconut oil during the day for energy and gut health. Long chain fatty acids (like olive oil, Omega-3, Omega-6) need more work and processies to be used as fuel and are preferably used for maintenance, repair (this is why they have such great health benefits) or are stored if we are in a calorie surplus.
- Number of double bond in the carbon chain
- Saturated fat = No double bond
- Monounsaturated fat = One double bond
- Polyunsaturated fat = Two or more double bond
The fat we store for future energy use is a mix of about 50/50 monounsaturated and saturated fat. It is the preferd type of fuel at the perfect ratio.
Polyunsaturated fat are essential fat (they act more like vitamins) but they make poor fuel source for the body.
Too much polyunsaturated fat as a percentage of calories on a well designed ketogenic diet is detrimental for many reasons. Sometimes I see people not reacting well to lower carbohydrate/ketogenic diet only because they eat a lot polyunsaturated fat sources like commercially available mayonnaise made with soybean oil. It is too much polyunsaturated fat to feel well! It’s better to make our own, with a light tasting olive oil or, less idealy, to buy commercially available mayaonnaise made with an olive oil/canola blend.
An equal quantity of olive oil and butter mix together would be very close to what is in our fat storage. The same goes for animal fat. Bacon, for instance, has a perfect 50/50 blend of monounsaturated/saturated fat.
Most fat sources are a combination of different length and double bond in the carbon chain.
In the context of a well designed ketogenic diet, where fat is the main source of fuel for the body: it’s important to keep an eye on the amount of polyunsaturated fat consumed (which is as little as possible Omega 6), correct the Omega-3/Omega-6 ratio with supplements and aim for the equal amount of monounsaturated fat and saturated fat.
Also staying away from Trans fatty acids found in: food fried in vegetable oil, margarine, vegetable shortening and anything that says partially hydrogenated oils on its label, is a general rule for any healthy diet, independently of its macronutrient combination.
The last point I want to make is about storing and cooking oil and/or fat. Fat is altered by heat, light, humidity and oxygen. Saturated fat is the most stable, then monounsaturated and lastly the most delicate is polyunsaturated.
Heat oxidation and rancidity are major issues for any fats. You should know the smoke point (burning point) and ideal storage conditions of the oil/fat you are using.
For instance, we should never fry/stir-fry extra-virgin olive oil. Its smoke point is very low (375°F) and heat destroys all the health benefits and denatures the fatty acids. If you want to use olive oil for cooking, it is better and cheaper to use extra light olive oil (468°F) and ghee (485°F) instead of butter (250°F).
Olive oil can be kept at room temperature for up to a year after its production date. If you buy in bulk, you should keep the big container in a cool place or the fridge and keep a small refillable bottle in the pantry. Raw nuts and seeds, rich in polyunsaturated fat are best kept in the fridge and will stay good for a year after it’s picked (sometimes you eat a nut and you can taste the rancidity, it’s bad!) Ghee can be kept at room temperature up to 3 months and salted butter a couple of days (unsalted butter cannot be kept at room temperature because there is no salt to protect it from molds and bacteria). If you like soft butter, a good tip is to make a 60/40 or 50/50 butter-oil mix and keep it in the fridge. It will have the consistency of a spread or margarine. You can use light olive or canola oil to preserve the taste of butter.
I hope it helps!