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Breaking b(re)ad: ketogenesis 101

If you are confused about what a ketogenic diet is, or what ketosis is for that matter, and are wondering whether or not this pattern of eating is the only way to burn fat (lose weight), stay a while. Chances are you're already somewhat familiar with at least a few of the following terms:






Okay I made that last one up. The point is, I see these words being tossed around all over the interwebs lately like they're the coolest words in the world. Like, nobody gave a crap about beta oxidation of fatty acids in Beatrice’s day. Zero people thought any of this was cool when I....I mean she, tried to share this info from her biochem book in undergrad. Flash forward almost a decade, and as luck would have it the ketogenic rodeo with all its fat oxidizing glory is in town and now your whole family and your dog wants to go.

Click play to meet Dr. Beatrice and plummet into the deep black hole that is the biochemistry of fat breakdown.

You are completely capable of understanding how your body works. The information highway today is complicated, mostly because topics like this are either oversimplified to the point where accuracy and precision are completely lost, or alternatively are presented with too many uneccesary details. While accurate and specific, these types of presentations make people want to pass out from boredom like the video above. Plus no one has a clue what the H any of it means. My hope for these education based entries is that I can provide you with a solid foundation that is helpful and useful to you whilst you get your fitness on. Let's go to keto-town.

What is ketosis?

"Ketosis is a metabolic state characterized by raised levels of ketone bodies in the body tissues, which is typically pathological in conditions such as diabetes, or may be the consequence of a diet that is very low in carbohydrates." -Merriam-Webster


To keep you alive, your body needs to produce energy. Your body can produce energy by breaking down macronutrients. The three main types of macronutrients your body can process and turn into energy are carbohydrates, fat, and protein. Carbohydrates are your body's PREFERRED fuel source, and fat comes in second. Protein can also be turned into energy, but as long as you are consuming calories from fat and carbs, your body won't tap into this as an energy source. If your body has no carbohydrate reserves, it turns to fat as an energy source. Fat is broken down to produce ketone bodies, which is what provides the fuel for the body when you're fresh out of carbs. If you stop eating carbs completely, you'll go into ketosis (because of all the fat breakdown) within a few days.

Why does the body prefer carbohydrates over fat as an energy source?

1) EASE OF BREAKDOWN: Fat molecules (tryglycerides) require more time to break down than carbohydrates. Carbohydrates from simple sugars (coca cola) are immediately available for energy production. This is why you experience a "sugar high" after eating a candy bar or drinking a soda. Carbohydrates that are more complex, like those that come from vegetables and grains, form long chains that we call polysaccharides (multiple sugars linked together). What's cool about these complex carbs is that they can still be broken down faster than fats, but in a time released fashion. This keeps your blood sugar from spiking really quickly. So, when it comes to speed, simple carbohydrates produce energy the fastest, followed by complex carbohydrates, followed by fats.

2) YOUR BRAIN LOVES CARBS. Your brain is VERY metabolically active. As such, it doesn't make sense that it would want to run off of a fuel source that takes longer to break down when there's a more "hot and ready" option available. Pizza pizza.

Think of this analogy: It's 5 p.m. and you haven't eaten all day. You're ravenous. At your home, you have a refrigerator in your kitchen and a freezer in your basement. Both have your favorite meal in them, except the one in the basement is frozen. Does it make any sense for you to walk to your basement, grab a frozen meal, defrost it, and then eat it when you've already got that same meal upstairs ready to go? Nope. Your upstairs fridge represents carbs. Your basement freezer holds fat. Fat just takes longer to convert into energy than carbs do.

Your body, being the incredibly smart machine that it is, is hardwired for survival. Carbohydrates are stored in your liver and muscles in the form of glycogen (long chains of carbohyrates linked together). Fully carb-stocked muscles and liver can provide only about 24-48 hours of energy for your body, whereas fat can supply you with energy for up to 3 weeks without any food. If we functioned only off of carbohydrates, we'd only last a few days (MAYBE) without food before our brain shut off. Thanks to fat stores in our body, we can survive during times of food shortage. So, if you quit eating carbohydrates, your body runs out of them after only a couple days before turning to fat as a primary fuel source for survival.

Your brain likes running on carbohydrates, especially glucose, which is delivered to the brain via the bloodstream. Fats, on the other hand, first get processed in the liver and turned into ketone bodies, which then move into the bloodstream and get delivered to your brain for energy. This is why a ketogenic diet is called a ketogenic diet.

Does my body burn carbohydrates AND fat during my workouts? How will a ketogenic diet impact my workouts?

Oooo-de-lally I love this question. As a self proclaimed HIIT (high intensity interval training) nerd, I often get questions as to how diet can impact exercise performance in high intensity workouts. The intensity and length of your workout impact the total number of calories you burn during a workout, as well as the percentages of fat and carbohydrates used as fuel during the workout.

Carbohydrates provide the energy during HIIT workouts.

If you routinely participate in traditional HIIT workouts, you know that the point of interval training is to work really hard for short periods of time (about 80% or more in terms of effort for 1-3 minutes, "breathlessness", anaerobic activity) and then recover for longer periods of time (active or full recovery). It is during anaerobic activity that the switch is flipped and your body starts to utilize more carbohydrates for energy than fat. This is because carbohydrates require less oxygen to burn than fat does (fat utilization is actually pretty minimal during anaerobic activity because of this). Translated, anaerobic means "lack of oxygen", so as exertion levels intensify and you move into your anaerobic threshold pace, you use more energy from carbohydrates, not fats.

This begs the question as to whether someone in ketosis can perform well in during a HIIT workout. And the answer is: kind of.

Because carbohydrates are the primary fuel for anaerobic exercise like HIIT training, fat alone can’t provide enough energy for this type of workout. This can make HIIT training feel like death for someone just starting a ketogenic diet. Feelings of heaviness, slugishness, and fatigue are par for the course if you're taking on HIIT and keto simultaneously. However, supplementing with carbohydrates (a serving or two of fast acting carbs such as fruit) before and after your HIIT workout should supply those on a ketogenic diet with just enough energy for the sole purpose of your HIIT session without causing you to come out of ketosis. Can you go to a HIIT workout with zero carbs in your system? Sure. Can you perform at your best potential during that workout and get the most out of it with zero carbs in your system? Not really.

You're at a greater risk of dehydration and electolyte loss on keto.

When you go keto and drastically lower carbohydrates, the glycogen (carbohydrate chains linked together) stores in your muscles and liver are depleted quickly (24-48 hours). Because every gram of glycogen holds on to roughly 3 grams of water, this means that as your glycogen stores are depleted, you start excreting more water. In other words, you're gonna pee a lot for the first few days of a ketogenic diet. The upside of this is that you're less bloated and feel "lighter" (in fact, your weight will decrease pretty quickly in the first few days due to this water loss). The downside? The side effects can make you feel pretty crappy (keto flu) because 1) Losing water through urine means you're at an increased risk of becoming dehydrated, which is no dice especially if you're losing even more water through sweat during workouts. 2) Losing water through increased urination also means you're losing electrolytes like salt and potassium as well, which keep you alive.

Bottom line: be mindful of hydration status on keto. Get plenty of fluids, have a little extra salt on your food, and be smart. If you're working out and sweating a lot while on a ketogenic diet, be even more mindful and take the necessary steps to prevent further water and electrolyte loss. Protect yo' self.

Bringing it home

Your body can use carbs, fats, and protein as fuel for energy. Your body likes to use carbs first if they're around. If they aren't, your body starts to break down fat as fuel. Ketones are products of fat breakdown. Build up of ketones in the blood = ketosis.

Marinate on this, and we'll continue this journey next week. If any questions regarding this information start to pop up, feel free to post them below! Burke and I love hearing from you. Don't be a stranger! We're all ears.

-Lee Ann



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