Getting into ketosis is fairly individual. How long it takes, how it affects performance, how you feel—all that stuff depends on your unique physiology and circumstances.
Me? I feel my best when I’m in ketosis. My mind feels sharp, my mood euphoric, and my hunger nonexistent.
All that considered, I DO take advantage of targeted carbohydrates from time to time. For example, I will take a bolus of glucose before jiujitsu. This is all dependant on the volume and intensity of the day, and although I may “leave ketosis” for a brief period of time, that’s not a concern under these circumstances. So long as I do not go too crazy on the carb intake (your carb tolerance could be far better than mine), it’s easy for me to reenter a ketogenic state as I’m keto/fat-adapted.
Keto-adapted, or fat-adapted, means my cells have adapted to burning fat and ketones for energy. Fat is my primary fuel. When I eat carbs, my primary fuel switches to glucose, but I’m never far from fat-burning mode.
Although I tinker with some additional carbs amidst my keto athlete lifestyle this is in the context of a LONG period of adaptation to low carb eating. A lot of people don’t stay low-carb long enough to properly adapt and this can cause a host of problems. As I've said many times, low carb and keto eating are not the best fit for everyone, but many of the folks who say “it didn't work for me” did not follow some simple rules like allowing for adequate time to adapt and making sure to dial in electrolytes.
Today we will look at how to get into ketosis with the keto diet, fasting, and a few other tricks. But first, there’s more to say about ketosis vs. keto adapting. Let’s dig in.
Ketosis vs. Keto-Adapting
If ketosis is your goal, you might think a positive test strip seals the deal. Technically, you wouldn’t be wrong. Ketosis is just the state of having elevated blood ketones—typically over 0.3 to 0.5 millimole/Liter (mmol/L) of beta-hydroxybutyrate (BHB), depending on who you ask.
But having ketones in the blood isn’t the same as being keto-adapted. An example will help.
Imagine you take a dose of exogenous ketones. (These are supplemental ketones). Your blood ketone levels will rise, 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 subsequent fatty acid oxidation. It makes sense. Your body senses ketones rising and shuts off fat burning. It’s a defense mechanism to prevent dangerously high blood ketone levels known as ketoacidosis.
So yes. You can be in ketosis and not fat-adapted.
The converse is also true. You can be fat-adapted and not in ketosis. I exit ketosis all the time, but I’m still good at burning fat. Which means I can re-enter ketosis rapidly.
So the goal here is to keto-adapt, which could take a few weeks depending on your metabolism. From here onwards, I’ll be talking about ketosis in the context of fat-adaptation. But understand there’s a difference.
How You Enter Ketosis
There are two main ways to enter ketosis: fasting and carb restriction. Both cause blood sugar and insulin levels to fall, which in turn signals your liver to start burning (beta-oxidizing) fatty acids. This fat burning produces ketones and ultimately, ATP, the energy currency of life on earth.
Let’s leave aside the ATP and focus on the ketones. Normally, your brain runs entirely on glucose. But when ketones are elevated, your glucose needs are reduced by a factor of four, and ketones supply most of the brain power.
In other words, ketones keep your brain chugging when glucose is scarce. Like during a fast.
The fact is, the human body can only store about 500 grams of glucose in muscle and liver cells. If you aren’t eating carbs, that 500 grams of glycogen evaporates rather quickly. It’s only 2000 calories worth of sugar, after all. Not exactly long-term rations, and keep in mind, due to an enzymatic quirk, once glucose is stored in the MUSCLE as glycogen, it does not get back out.
But body fat... there’s plenty of that, even on a lean person. A quick example will help illustrate.
Let’s imagine a 200 pound man with 12% body fat. That’s 24 pounds of fat on a fairly lean dude. Now let’s calculate the calories stored in his body fat:
- 24 pounds of fat = 10,886 grams of fat
- 1 gram of fat = 9 calories
- 10,886 grams of fat * 9 calories = 97,974 fat calories
This is why we like burning body fat. It’s not running out any time soon.
I know I know, not every gram of body fat can be used for energy. Some is needed for normal physiologic functions.
But still, a little body fat goes a long way. And relevant here: Fat is the raw material from which ketones are made.
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 garners all the benefits listed above.
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, but not using them. This keto-adaptation problem won’t show up on a blood test.
Plus, outside narrow considerations (like controlling childhood epilepsy), nobody knows what ketone levels are optimal.
#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, like:
- Weight loss
- Energy levels
- Mental function
- 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 titrating carbs up a bit.
Tips To Get Into Ketosis Faster
Here are some simple strategies to accelerate your transition into ketosis.
#1: Intermittent fasting
Intermittent fasting (IF) is like an internal keto diet. Instead of burning dietary fat for energy, you burn body fat.
Fasting is synergistic with the keto 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 IF. Some involve daily fasts of 12, 16, or 24 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.
#2: Limit carbs
On keto, you typically limit carbs to under 10% of daily calories. Around 20 grams per day.
Keeping carbs low keeps blood sugar and insulin low, which in turn sends the ketosis bat signal. Carb restriction is, in fact, the single most important factor for entering ketosis.
Some folks find cutting carbs easy, 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. Once you break the sugar addiction, everything gets easier.
#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 bad data from the 1950s. More recent data—like these two meta-analyses on nearly one million people—shows no link between saturated fat consumption and cardiovascular disease risk. (Link 1, Link 2) 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.
Start slow with MCT oil (maybe a teaspoon) and work your way up. If you choose to ignore this advice, keep some adult diapers handy.
#5: Try Exogenous Ketone
We talked about exogenous ketones earlier. They’re basically ketones—in the form of 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 won’t 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 latest book Wired to Eat, you know how much individual differences affect our responses to food. Keto may be the optimal longevity diet for one person, but a crappy choice for another.
I suggest you view ketosis is a tool. A temporary state with some sweet potential benefits.
And don’t be afraid to carb cycle once in a while. You can always return to keto mode, especially once you’re keto-adapted. And, if you find that you generally run best near Keto Avenue...well, now you know!