As explained in a previous post, ketones are only produced in the absence of insulin, and that requires a very daily carbohydrate intake. That threshold varies for each person, but an upper carb limit of 30 grams/day will initiate ketone production for 99+% of the population, usually within just a few days.
Stripping carbohydrate intake to just 25 grams a day is a big change for most people, since you’ll soon run out of your body’s preferred energy supply.
YOUR BODY ON CARBS
Under a more “traditional” diet, here’s what happens when you eat carbs:
- You consume a high-carb meal, causing your blood sugar to rise. That sugar gets broken down into glucose, prompting your pancreas to produce insulin.
- Insulin allows your cells to use glucose for energy. Unused glucose is stored as glycogen in the liver and muscles.
- As your blood sugar falls, your pancreas produces glucagon, signalling your liver and muscles to release stored glycogen, which converts back to glucose, providing your cells with energy. Any extra glucose not used by the cells will be stored as fat.
- As you run out of stored glycogen, your blood sugar runs low, causing your cells to become starved for energy. You feel dizzy, irritable and weak, prompting you to eat more carbohydrates. Your blood sugar then rises, and the whole cycle begins again.
YOUR BODY WITHOUT CARBS — WHAT SHOULD HAPPEN
If you decide to fast, or eat a very low-carb diet, here’s what the process should look like:
- Once you run out of glycogen, your body starts tapping into your fat cells (or dietary fat, if available), releasing fatty acids into your body.
- As fatty acids build up in the liver, they get converted to ketones, which are then released into the bloodstream. These ketones provide an alternative fuel source for your brain and cells, when glucose is not available. It typically takes about three days for your body to start produce ketones, once you stop eating carbohydrates.
While your glycogen stores are limit to about 2,000 calories, your fat store are virtually unlimited, even if you have a very lean build. And that’s the beauty of being fat-adapted — you (almost) never run out of energy.
YOUR BODY WITHOUT CARBS — WHAT ACTUALLY HAPPENS
If you’re like me, you’ve likely spent your whole life eating a high-carb diet, constantly topping up your glycogen stores, snacking on “healthy” fruit and whole-grains every few hours, to make sure your blood sugar never runs low.
My body was addicted to sugar, preferentially burning glucose for energy, which was always readily available. I couldn’t go without carbs for more than a few hours without feeling tired and moody.
If that sounds like you, then this is what actually happens when you first make the switch to a low-carb diet:
- Your glucose level drops, depriving your brain of energy (sugar crash).
- Your dopamine[1] levels also drop, triggering withdrawal symptoms, such as anxiety, fatigue and brain fog.
- You start desperately craving carbohydrates, your body conspires against you to top up your blood sugar.
- Once you completely deplete your glycogen stores, you literally “hit the wall” and feel like you might throw-up or pass out (or both)[2].
This is the dreaded keto flu, and this is where most people give up. This is when you hear the phrase “I tried going low-carb once, and it felt like crap, so it must be a really bad idea.” This happens because they didn’t push past this point, and never got over the keto flu.
WHAT GOES WRONG AT THE BEGINNING
Although we’re all wired to use fat stores when glycogen get depleted, this process is very inefficient at first, especially if you’ve been burning sugar your whole life. Even a small increase in carbohydrates at this initial stage will stop ketone production, and switch you back to sugar-burning mode.
At this point, you have two options — eat some carbs, and delay the initial induction phase, or suck it up and trust that your body will eventually switch to fat-burning mode.
If you decide to stick it through, your life will suck for a week or so before things finally start to get better.
WHAT TO EXPECT THE FIRST FEW WEEKS
Aside from fatigue and irritability, here’s what else you can expect the first few weeks after starting a ketogenic diet:
- Water loss: Every gram of glycogen stores 3 to 4 grams of water. Therefore, retained water will also be released as your glycogen levels drop, so you will experience many trips to the bathroom at first, and a corresponding drop in body weight. For the average sized person, you can expect about 1% weight loss per week for the first few weeks, which works out to 1.5 lbs/week for an 150 lb person.
- Headaches: As you release water, you also release electrolytes — namely, sodium, potassium and magnesium, which can trigger headaches and even migraines in some people[3].
- Smaller bowel movements: For most people, a standard keto meal will be much smaller than a “traditional” meal, and will therefore result in smaller bowel movements. This is perfectly normal.
- Digestive distress: Although I never experienced this myself, I have read reports of digestive problems, like constipation, indigestion and diarrhea. If you’ve been eating a low-fat diet for a long time, you may lack the enzymes to properly digest fat. Suddenly adding a lot of fat to your diet when making the switch to keto can be a shock to your system. However, this is just temporary.
- Drop in strength and aerobic capacity: If you regularly exercise or participate in sports, you’ll find your energy levels really lacking in the first few weeks, as your body struggles to tap into its backup energy reserves. You can expect a drop in performance, and general decline in motivation the first few weeks of your transition.
TIPS FOR GETTING OVER THE KETO FLU
It’s important to note that for most people, this initial ” really unpleasant” phase only lasts a few weeks, but here are a few tips to make your transition a little less painful:
- Go easy on making changes: As noted in the previous post, a slower transition to low-carb living will shorten and help minimize the keto flu. Switching from a very high-carb/low-fat diet to less than 25 grams of carbs per day is a significant change, and you can therefore expect more significant withdrawal symptoms. If this is the case for you, you might want to consider making smaller dietary step-changes.
- Be sure to eat enough fat: It’s critically important to eat enough dietary fat, as this will provide a good portion of your energy supply (any shortfall will come from body fat). A big mistake most people make is not eating enough fat, either because of conditioning (since we’ve all been raised to believe fat is bad for you) or a desire for very rapid weight loss. This is an error I made in my first attempt to go low-carb two decades ago, which eventually caused me to give up completely. Remember, keto is a low-carb, high-fat diet, where 75% of your energy requirements come from fat. A low-carb/low-fat diet results in severe calorie restriction. It may put you in ketosis faster, but it will also drop your metabolism in the process. And this is not sustainable in the long run.
- Don’t go crazy with the protein: Many people go overboard on protein when they get hungry. This is usually because they’re too afraid to eat more fat, so protein feels “safer” and more satiating. However, as noted in a previous post, protein will convert to glucose, so eating too much protein will kick you out of ketosis. Therefore, don’t go crazy with the protein, especially at first.
- Go crazy with the salt: To compensate for all the loss of electrolytes, it’s imperative to top up your sodium, potassium and magnesium stores. This is something I neglected to do at the very beginning, and suffered dearly about one month after starting my low-carb journey. Like most people, I’ve eaten a very low-salt diet for most of my life, and it felt wrong to add so much salt to my food. However, since you’re no longer eating carbs, you’re no longer producing as much glycogen, which hinders your ability to retain water and electrolytes (yes, you read that right — carbohydrates cause water retention, to a much greater extent than salt[4]). You eventually want to work your way up to about 15 grams of salt[5] per day, about 10 times government guidelines. Brain fog, headaches and fatigue are the primary symptoms of low sodium levels, so don’t be afraid to go crazy with the salt.
- Don’t forget the other electrolytes: Aside from sodium, potassium and magnesium are the two other minerals that get flushed out as you begin to drop water weight. While magnesium is fairly easy to get through your diet, potassium will likely need to be supplemented. If you’re experiencing muscle cramps or heart palpitations, then you need to top up your potassium stores. The easiest and cheapest way to do this is through a low-sodium salt, which is typically a mix of sodium and potassium chloride[6]. The average person needs about 4 grams of potassium and 400 mg of magnesium per day. Bone broth and avocados are the highest source of potassium. If your diet does not include seeds, nuts, avocados and leafy greens, you might also want to consider a magnesium supplement[7].
- Trim back on foods that are hard to digest: While suddenly going cold-turkey on carbs can be a shock to your system, the same is true for suddenly adding half a pound of fat to your diet, especially if you’ve been eating “fat-free” for most of your life. Try to slowly bump up your fat intake, adjust according to your energy levels, and go easy on foods that can be harder to digest, such as coconut oils, eggs and avocados. Digestive distress is temporary, and will go away once your gut bacteria is completely restored.
- Take it easy at the gym: The first few weeks of keto is not the ideal time to run a marathon or go for a PR at the squat rack. You should dial back the intensity until your energy levels return to normal, or just do some light, restorative exercises. As a side note, people who exercise regularly have an easier time getting into ketosis, as they are more accustomed to low glycogen levels. So no need to skip the workout completely.
- Avoid the temptation to cheat: The worst thing you can do when first starting a low-carb diet is — well, eat carbohydrates. Although it will be tempting to top up your blood sugar, this will quickly stop ketone production and delay ketosis. Commit to the process, stay the course and don’t deviate at the beginning. It will eventually get easier once your body learns to use its fat reserves.
Although everyone’s experience is different, you can expect this phase to last anywhere from a week to a month. Again, a lot depends on your individual metabolism, insulin sensitivity and how drastically you’ve changed your diet.
Once you’ve made it past this point, you’re not out of the woods yet. Next comes the induction phase, where things start to get really interesting.
NOTES:
1 Consuming carbohydrates releases dopamine, a neurotransmitter that makes you feel happy and content. This is what makes sugar just as addictive as cocaine. So you can expect similar withdrawal symptoms as with any other addiction.
2 Your glycogen stores are limited to about 2,000 calories, which works to roughly 2 hours of vigorous exercise. I experienced this “bonk” first hand during a half-marathon in 2013 (pre-keto). The race lacked a post-run feeding station, where you would normally find high-carb foods (bananas, orange juice and bagels) to quickly replenish your blood sugar. After running for more than 2½ hours, I felt dizzy and nauseous, and would later pass-out in my hotel suite. Not a pretty sight.
3 The folks at Virta Health have a more technical explanation of why mineral supplementation is critical when following a ketogenic diet.
4 It’s recommended to minimize salt intake when carbohydrate intake is high. Since carbs cause water retention, and blood is over 90% water, a high-carb diet can lead to high blood pressure. This is explains why government health guidelines advocate minimal salt intake, since it is assumed most people consume plenty of carbs. If you suffer from high blood-pressure, it is greatly advised to closely monitor pressure and salt-intake, preferably under the supervision of a qualified professional.
5 Table salt is sodium chloride (NaCl), which is only 40% sodium. Therefore, 10 grams of table salt only contains 4 grams of sodium.
6 Morton Lite Salt is the keto standard, although this is generally only available in the US. In Canada Windsor Half Salt and Plochman’s Low Sodium Salt are readily available at most big box stores. All three are about 20% sodium and 25% potassium. Since your body sheds potassium when sodium runs low, low-sodium salt should be added in addition to regular table salt (not instead of).
7 There’s been a lot of publicity around magnesium deficiencies in recent years, which some believe to be the primary cause of migraines. I’ve tried many forms of magnesium supplements over the years, including Natural Calm, a magnesium citrate powder. I eventually gave it up, since magnesium naturally lowers your blood pressure, and my blood pressure is already too low.