Getting into ketosis has the same basic requirement for everybody: Limit carbohydrate intake below 50 grams of net carbs per day. But how you enter ketosis — how long it takes and how it makes you feel and perform — depends on your unique physiology and circumstances.
Even assuming you benefit from a ketogenic state, it may be overly hasty to ask how to get into ketosis. I prefer to start with questions of when or if.
For example, when I’m already in ketosis and I have a longer, more intense jiu jitsu session, I choose to take advantage of targeted carbohydrates in the form of glucose. I may “leave” ketosis for the duration of my training session, but that’s not a concern under these circumstances. So long as I don’t consume carbs in significant excess, it’s easy for me to reenter a ketogenic state because I’m fat adapted, AKA keto adapted.
“Fat adapted” means my cells have become accustomed to burning fat and ketones for energy. So when I eat carbs, my primary fuel switches to glucose — but I’m never far from fat-burning mode.
It’s important to note that fat adaptation develops over a long period of low-carb living. And while the ketogenic diet is certainly not an optimal fit for everyone, in many cases people simply haven’t eaten a ketogenic diet long enough to properly adapt and reap the full benefits.
With that in mind, this article will address ketosis, its potential benefits, how to measure it, and some tips on kick-starting it. Let’s dig in.
Ketosis vs. Fat Adapting
Ketosis is simply the state of having elevated blood ketones. Elevated, in this context, just means over 0.3–0.5 mmol/L of beta-hydroxybutyrate (BHB).
But as I alluded to a moment ago, being in ketosis is not the same as being fat adapted. Imagine you take a dose of exogenous ketones (supplemental ketones). Your blood ketone levels will rise, and you’ll be in ketosis!
But will your underlying metabolism shift towards fat-burning? No. In fact, exogenous ketones have been shown to lower free fatty acids in the blood and the fat burning which follows. It makes sense. Your body senses that ketone levels are rising and shuts off fat burning. It’s a defense mechanism to prevent dangerously high blood ketone levels, known as ketoacidosis.
Therefore, you can be in ketosis and not be fat adapted. The converse is also true. You can be fat adapted and not in ketosis. I leave ketosis periodically, but my body is still wired to burn fat when those carbs run out. That means I can re-enter ketosis more quickly than someone who is not keto adapted.
I say all this to bring a very important point home: Fat adapting is the goal, not ketosis. And fat adapting can take a few weeks, depending on your unique metabolism. With that framework laid, let’s talk more about ketosis now.
How You Enter Ketosis
Normally, your brain runs entirely on glucose. But the fact is, the human body can only store about 500 grams of glucose in muscle and liver cells. And due to an enzymatic quirk, once glucose is stored in the muscle, it can’t get back out. So if you aren’t eating carbs, that 500 grams of glycogen can evaporate rather quickly. It’s only 2000 calories worth of sugar, after all.
But body fat? There’s plenty of that, even on a lean person. Imagine a 200 pound man with 12% body fat. That’s 24 pounds of fat on a fairly lean dude — and 24 pounds of fat is equal to 10,886 grams. At 9 calories per gram of fat, he’s holding almost 98,000 calories. That’s not running out any time soon!
Of course not every gram of body fat can be used for energy — you need fat for normal physiological function. But a little body fat can go a long way. And relevant here: Fat is the raw material from which ketones are made.
There are two main ways to enter ketosis: fasting and carb restriction. Both deplete glycogen stores and minimize blood sugar and insulin levels. This shift signals your liver to start breaking down fat into fatty acids and using them to produce energy. Burning fatty acids — known as beta oxidation — produces ketones which are later used to create adenosine triphosphate (ATP), the energy currency of life on earth.
When ketones are elevated, your glucose needs are reduced and ketones supply most of the brain power. In other words, ketones keep your brain chugging when glucose is scarce.
Ketosis Benefits
Let’s quickly hit on the benefits of ketosis, then I’ll explore how to measure it.
- Fat loss. When you first try a keto diet, you may lose a few pounds, but these pounds are likely water weight from lost glycogen. Real fat loss requires fat adaptation, and may take weeks.
- Less hunger. High-fat diets have been shown to reduce hunger hormones like ghrelin and CCK. Less hunger, less overeating.
- Brain function. Ketones cross the blood brain barrier and fuel the brain with clean, efficient energy.
- Stable energy. Body fat—when accessible—is a nearly unlimited energy source. No more blood sugar crashes.
- Lower inflammation. The research is early, but ketones appear to suppress the chronic inflammation underlying most age-related diseases.
The above is generally applicable to most folks, but it is worth noting, not everyone will experience all of the benefits listed above.
Measuring Ketosis
How do you know if you’re in ketosis? You measure it. You can do this a couple different ways:
#1: Ketone Level Testing
To monitor your progress with keto, it makes sense to occasionally check ketone levels. If you’re above 0.5 mmol/L BHB, you’re in ketosis.
Ketones can be measured in the blood, breath, or urine. Blood testing, which can be done at home with a meter and test strips, is the most validated method — but breath and urine tests can be useful too.
The problem with relying on ketone levels to gauge your success? For one, you might be producing ketones without using them efficiently. This keto adaptation problem won’t show up on a blood test.
#2: Personal ketosis metrics
I understand the temptation to simply measure blood ketones and call it a day. But might I suggest other metrics to optimize for? Rather than make ketosis your goal, how about:
- Weight loss
- Energy levels
- Mental function
- Appetite
- Sleep
- Athletic performance
These should be improving, or at least not declining. After all, improving these markers is why you went keto in the first place, no? Plus, these markers give a better sense of keto adaptation than ketone levels.
It’s also crucial to monitor your bloodwork (especially tests pertaining to heart health) on a keto diet. Some folks see big elevations in LDL cholesterol on keto. If you’re one of them, consider adjusting fat sources to include more monounsaturated fat and/or consuming a bit more carbs.
Tips To Get Into Ketosis Faster
Here are some simple strategies to accelerate your transition into ketosis.
#1: Intermittent fasting
Intermittent fasting is similar to, and can synergize well with, a ketogenic diet. Why? Because both regimens provoke metabolic changes — low insulin, low blood sugar, increased fat oxidation, etc. — that complement one another.
There are many forms of intermittent fasting. Some involve daily fasts of 12–18 hours, while others alternate fasting and feeding days on a weekly schedule. My advice is to start with a 12 hour daily fast, then incrementally build to longer fasts. Listen to your body and back off where it makes sense — this is meant to improve your health, not make you miserable.
#2: Limit carbs
Carb restriction is the single most important factor for entering ketosis. On keto, you typically limit carbs to under 10% of daily calories. Around 50 grams per day. Keeping carbs low keeps blood sugar and insulin low, which in turn sends the bat signal to your brain: “Calling all ketones!”
Some folks find cutting carbs easy, while others find it excruciating. The world doesn’t make it easy. Hidden carbs are everywhere — even tomato sauce can have upwards of 20 grams of sugar per serving.
To stay on top of your carb count, download a macro-tracker like Chronometer. Just input your foods and out pops a detailed summary. The good news is that carb cravings tend to fade after you fat adapt. If you’re struggling with carb cravings, give this article a read.
#3: Increase fat calories
Fat is the stuff from which ketones are made. After you swallow fat (as triglyceride), you digest and split those triglycerides into fatty acids. Then you either burn fatty acids directly (typically in the muscle) or convert fatty acids in your liver to make ketones.
But dietary fat does more than boost ketones. Fat helps you:
- Build cell membranes
- Stay full by increasing satiety factors (but don’t skimp on protein!)
- Absorb fat-soluble vitamins A, D, K, and E
- Create ATP, your energy currency
You might be worried that fat (especially saturated fat) increases heart disease risk. But this belief is based on lofty data from the 1950s. More recent population data — like meta-analyses on nearly one million people — shows no link between saturated fat consumption and cardiovascular disease risk. Also, this is a great look at how although LDL-Cholesterol may increase for some following a low-carb diet. The net effects are arguably beneficial with regards to cardiovascular disease potential.
#4: Take MCT Oil
Medium-chain triglycerides (MCTs) are the most ketogenic form of fat. When you consume MCT oil, it goes straight to your liver for ketone production.
The brain benefits are measurable. In one study, elderly folks had better working memory and attention after dosing MCTs. But don’t go all-in with MCT oil. Start slow — with a teaspoon perhaps — and then work your way up. If you choose to ignore this advice, keep some adult diapers handy.
#5: Try Exogenous Ketones
We talked about exogenous ketones earlier. They’re basically ketones — beta-hydroxybutyrate (BHB) — attached to sodium, potassium, calcium, magnesium, or alcohol molecules.
Although exogenous ketones originate outside your body, they’re indistinguishable from ketones made inside your body. Same substance.
Taking exogenous ketones will not accelerate your fat adaptation, but it will boost your ketones, temporarily decrease blood sugar levels, and possibly enhance cognition.
Ketosis Is A Tool
Before I sign off today, I want to make a quick point. Ketosis can be beneficial, but it’s not for everyone or every situation.
The truth is, we don’t know much about the long-term effects of sustained ketosis. I suspect it depends on the person. If you’ve read my book, Wired to Eat, you know how much individual differences affect our responses to food.
Keto may be the optimal diet for one person’s longevity, but a bad choice for another. On that note, don’t be afraid to carb cycle every once in a while. You can always return to keto mode, especially once you’re keto adapted.
I suggest you view ketosis as a tool. A temporary state with some sweet potential benefits, especially in the context of being fat adapted.
