Keto 101 [The Complete Beginner’s Guide]

keto 101 - the complete beginner's guide to a ketogenic diet

In recent years, keto has gotten super trendy.  

But even most of the people who try it don’t really understand how it works, and often don’t do it right.  

Today we’re gonna fix that.  

In this post I’ll explain everything you need to know as a beginner getting started with keto.  That includes the physiology, benefits, what to eat, how to track your progress, keys for success, and more.    

I’ll also share my personal experience with the ketogenic diet, and why it’s such a natural fit with fasting.   

Let’s dive in.  

Keto Physiology Made Simple

You’ve probably heard that a ketogenic diet is low carb, high fat.

That’s because when you eat a lot of fat, and mostly avoid carbs, your liver starts making something called ketones (a.k.a. “ketone bodies”).

Ketones are made FROM fat–either dietary fat or body fat.

Ketones function as an alternative energy source for your brain and body, in place of sugar (glucose).  That’s why your body makes ketones when there’s not a lot of glucose around (i.e. eating low-carb, or fasting).  

Ketones travel around in your bloodstream (just like blood sugar), and provide energy to your brain and the rest of your body.  As ketones take over and become your dominant energy source, your blood sugar gets lower.  And that’s a good thing.  

There’s a basic overview, but if you’d like to understand more about ketones I’d highly recommend you watch the first 6 minutes of the video below:

(If you want to hear a little bit more about Dr. Attia’s story, back the video up to about the 3 minute mark.  I set it to start where he first talks about ketosis, since that’s the most relevant to this post.)  

My Experience With the Ketogenic Diet

I first heard of the ketogenic diet back in med school. It was mentioned in passing as kind of a last resort treatment for kids with seizures.  

Almost 10 years later (in 2016), I decided to learn more about it after hearing Tim Ferriss mention it a couple times on his podcast.

So I watched a lecture about it online (the video above), and got kind of excited to try it myself.  Even though I had previously taken several biochemistry classes and learned about ketones, I never really thought that much about the health implications until I watched that.

A couple months later, I started.  

I wasn’t really sure what to eat, so I checked out a few blog posts and started looking up nutrition info for various foods, and making a list.

list of macros for several common foods on ketogenic diet
Overly-detailed food list I made when I first started keto 🙂

I also read The Ketogenic Diet (the original book written about treating seizures with a ketogenic diet), which gave me a little more perspective on what to eat, among other things.

I was a little clueless at the beginning, but knew enough to know that I needed to measure my ketones to see if I was actually in ketosis (i.e. ketones in my blood).  So I got some urine test strips, and checked a couple times a day.   

After a few days the strips turned positive, and generally stayed positive thereafter.  Several months later I got a ketone breath tester, which was a little more convenient and less messy.

(I haven’t purchased a blood ketone meter yet because the test strips are a lot more expensive, and it never seemed that important.)

The first time around, I tried the ketogenic diet for about six months with a few short breaks (mainly for holidays).  Since then I’ve done it off and on, for weeks or months at a time here and there, often in conjunction with some type of fasting or time-restricted eating.  

One major benefit I’ve noticed personally is that eating high-fat and low-carb helps control my cravings, so it’s a lot easier to avoid binging on sweets or other junk food.  

It also helps control my weight, improves my mental focus, and makes any type of fasting a lot easier–especially prolonged fasting (> 24 hours).  

Why Does Keto Make Prolonged Fasting Easier?  

Overall, it’s pretty simple:

When you fast, your body gradually switches over to “fat-burning mode”.  In other words, fat (and ketones made from fat) become your dominant source of fuel, instead of sugar.

fasting timeline - first 3 stages of fasting

If you just start fasting out of nowhere, it takes a while to make this transition. So you’re more likely to have some energy lulls while you’re switching over.  

But if your ketones are already high, you get a head start and hit the ground running.

a ketogenic diet makes extended fasting easier

It also helps if you’ve been doing a ketogenic diet for a while. Because the longer you do keto, the more “fat-adapted” your body becomes.

In other words, your body becomes more efficient at using fat and ketones for energy, because it makes more of the enzymes and other machinery needed for that process.  

In general, it takes a few months to become reasonably fat-adapted. Once you’ve done that, your metabolism is more flexible and fasting of all varieties becomes easier. 

Don’t get me wrong, you can still get a lot of health benefits from fasting even if you never try eating a ketogenic diet. But eating high-fat, low-carb allows you to get some of the benefits of fasting more quickly.  

Health Benefits of A Ketogenic Diet

The way I see it, there’s one gigantic benefit from keto, and then a bunch of other related ones.

Just like fasting, eating a low-carb / high-fat ketogenic diet helps normalize your blood sugar and insulin levels.

That alone is HUGE.  

Why Does Normalizing Insulin Matter so Much?

Remember insulin?

It’s that hormone our pancreas pumps out whenever we eat sugar or other carbohydrates, and it plays a big role in growth and energy storage throughout your body.  

These days, most US adults have excessively high insulin levels (from all the processed food we eat), and those high insulin levels are at the root of almost every chronic disease….so normalizing insulin is a MASSIVE benefit!

I can’t really emphasize that enough.

Most of the other benefits that come from eating a ketogenic diet are at least partially related to normalizing blood sugar and insulin levels. 

Benefits of a ketogenic diet

For example, by dropping insulin levels you “release” your body fat, which makes it easier to lose weight on a ketogenic diet.  

And by definition, normalizing blood sugar means you dramatically improve (or eliminate) type 2 diabetes, and prediabetes.

Similarly, normalizing insulin is a critical component to preventing other illnesses, like high blood pressure, kidney failure, heart disease, dementia (e.g. Alzheimer’s), and more.  

In case that’s too abstract, here are a few other specific benefits of nutritional ketosis you might like to know about: 

Consuming Fat Keeps you Satisfied and Controls Cravings

By consuming more dietary fat on a ketogenic diet, you stimulate satiety hormones such as CCK, which means you’ll feel satisfied for a long time.  In other words, you won’t get hungry as often, or have as many cravings for sugar and other junk food.   

On a related note, a ketogenic diet can be really helpful for people who are addicted to sugar (which appears to be quite common, and even more common among diabetics).     

Low-Carb is Good for Your Mental Health

There’s a big focus on mental health in the news lately, and for good reason.

More and more people are struggling with anxiety, depression, and similar problems.  Especially young people. 

(By the way, social media use is clearly a major contributor to the increase in anxiety and depression, if not the #1 cause.  If that seems surprising, try watching The Social Dilemma on Netflix.)

In many cases, a ketogenic diet can reduce or eliminate symptoms from conditions like anxiety, depression, bipolar, schizophrenia, ADHD, and even autism.

Ketones can also help a lot with dementia, which is a slightly different type of “brain problem”.  And they obviously help with seizures, which also originate in the brain.  

In short:  Ketones seem to be good for your brain.    

For an introduction to mental health and nutrition, check out psychiatrist Georgia Ede’s lecture below:

You can also find many other resources about low-carb and mental health on her website

A Ketogenic Diet Can Eliminate Migraines

Turns out, if you have migraines and you switch to a ketogenic diet, there’s a good chance your migraines will go away.

The exact mechanism is not totally clear, but like many things it’s probably related to insulin.

(For a deeper explanation and references, check out this book.  Or start with this podcast episode.)

And Many More Benefits — That Was Just a Teaser!

I didn’t try to list all the benefits of a ketogenic diet here today.  That would take too long!  

It’s also an active area of research, so new benefits are being discovered all the time. 

Suffice it to say, nutritional ketosis has many other health benefits, but hopefully that was enough to whet your appetite.

What to Eat on a Ketogenic Diet 

Maybe you’re thinking, “The science sounds interesting, but what do I actually eat?”

The basic rule of thumb is to avoid things that are grainy, starchy, or sugary. In other words, limit your carbs.

What does that leave?

Foods that are low in carbs, but high in fat and/or protein.  Overall, the more fat the better, because you want to get about 70% or more of your calories from fat.

Options include things like meat, fish, poultry, cheese, nuts, seeds, butter, olive oil, coconut oil, eggs, avocados, berries, leafy greens, and other non-starchy vegetables (i.e. no potatoes, sweet potatoes, or corn).  

keto food options

Personally I take a pretty simple approach using mostly whole foods that don’t require a lot of preparation, or can be cooked in just a few minutes.

I also use a lot of salt and other seasonings, because:

  • A) My body needs extra salt on keto 
  • B) I like my food to taste good  

So don’t forget the salt and spices!!  

If you’d like to see some more specific examples, I also shared a long list of keto food options in a separate blog post. 

If you like cooking, many of the ingredients I listed there are easy to combine in a frying pan, for example–along with salt and seasonings!  With a little practice, it’s actually pretty easy to create delicious combinations.  

If you don’t like cooking…many of the options on that list require almost no prep.  

What About Fancy “Keto Recipes”?

Keto has gotten popular enough that there are tons of low-carb recipes out there.  You can make low carb bread, low carb pizza, low carb cookies…. whatever tickles your fancy.

Personally, I don’t bother.

First of all, it’s really time-consuming. Second, it’s probably not as healthy because you’re using lots of processed ingredients.

But hey, if that’s what it takes to get you to try a low-carb diet, I’d say go for it.

How About Packaged Keto Products?

Several companies have tried to cash in on the keto craze by creating lines of packaged keto foods and supplements.  

Some are better than others, but there are a few things you should be aware of-

First, some of those products (especially the “keto treats”) have a lot of artificial sweeteners.  That’s one way to get your sweet fix without sugar, but artificial sweeteners aren’t exactly ideal for your health.

Second, many products marketed as “keto” aren’t really low in carbohydrates. They just put the word keto on the label so unsuspecting customers will buy it without looking that closely at the details.  

The bottom line?

Pay attention to how many grams of carbohydrates are actually in the food, even if it says “keto” or “low carb” on the package.  

Tracking Your “Macros”: Fat, Carbs, & Protein

Part of eating a ketogenic diet is learning more about what’s actually in your food.

When I first started keto, I had a lot to learn about how much carbohydrate, fat, or protein was in specific foods. 

You’ll probably have a similar experience when you start paying attention to those details,  so get ready for some surprises!

When tracking these “macronutrients” (fat, carbs, & protein), there are basically two things to focus on:

1. Keep Your Fat High

To get into ketosis (i.e. have ketones in your blood), you’ll probably need to get about 70% or more of your calories from fat.  

ketogenic diet food pyramid fat protein carbs

So if you want to, you could just look at the “calories from fat” in each type of food that you eat, and try to keep it over 70% on average.  

2. Keep Your Carbs Low

Another rule of thumb is to keep your total carbs under about 30 grams per day (the specific number varies depending on whom you ask).  

Notice in this case I referred to “grams” instead of calories.  Here’s how those are related to each other.  

  • 1 grams carbs = 4 calories
  • 1 gram protein = 4 calories
  • 1 gram fat = 9 calories

Notice a gram of fat has about twice as many calories as a gram of carbs or protein.  That’s the main thing to keep in mind if you’re ever doing calculations.  

Food labels usually tell you the “total calories” and “calories from fat”, as well as how many grams there are of fat, carbs, and protein.  So all that info is available.  

What’s This Thing About “Net Carbs”?

Basically it means you don’t count fiber towards your total carbs.

Nutrition labels include fiber in the total carbohydrate count. But that doesn’t really make sense, because you can’t fully digest or absorb fiber, and it’s not going to raise your blood sugar like other carbohydrates.

So when tracking your carbs, subtract fiber from the total.

For example, an average sized avocado has about 13 total grams of carbs, and about 9 grams of fiber. Start with 13, subtract the 9 grams of fiber, and you’re left with 4 grams of “net carbs” in an avocado.  

With whole/natural foods, this makes a lot of sense.  So go ahead and subtract the fiber.  

With processed foods it gets a little more hazy, because they often artificially boost the fiber to skew the numbers.  And in addition to the fiber, they also subtract sugar alcohols (like erythritol, xylitol, etc) from the total carbs, even though those are partially absorbed into your bloodstream.  So it’s not always totally legit.  

Here’s the bottom line:

Subtracting fiber from total carbs in whole foods is reasonable.  

On packaged keto products, “net carbs” is more of a marketing ploy than a helpful number.  So take it with a huge grain of salt.  

Keys to Success (and Common Pitfalls) With Keto

From what I’ve observed, here are some of the main keys to success when you start with keto.

Ease Into it Slowly

If you suddenly drop your carbs way down, you’re more likely to experience what’s called “keto flu”.

Keto flu basically means not feeling that great while your body is still adapting to lower carb consumption.  It may include symptoms like fatigue, dizziness, or low mood.

Keys to success when starting a ketogenic diet

Most of us have been dependent on carbs and sugar for many years, so it makes sense that we’d experience some growing pains when we start taking them away.

A better approach?  

Try to ease into it more slowly, so that your body can gradually adapt.  In practice, that might look something like this:

  • Week 1:  Up to 150 grams of carbs per day
  • Week 2:  100 grams per day
  • Week 3:  75 grams
  • Week 4:  50 grams
  • Week 5:  40 grams
  • Week 6:  30 grams

Even while you’re making that transition, you’ll still experience some health benefits. And without all the pain of the “keto flu”.

Starting slowly also makes you more likely to stick with a new habit. So it’s a win-win.

Don’t Forget Salt!  

Remember how most people have excessively high insulin?

High insulin causes our kidneys to retain more salt and water, which is one of the main reasons so many people have high blood pressure.

Once you start cutting back on carbs, your insulin goes down, and you urinate out more salt/sodium.  You probably won’t be eating as much sodium either, since we get most of it from processed foods.  So it’s a double whammy. 

As a result of excreting more sodium (and consuming less of it), your blood pressure decreases.  That could be a good thing to some extent, but if you’re not used to it you might feel dizzy, fatigued, or otherwise unwell, at least at the beginning.

Hence the need for SALT.

getting enough salt is very important on a ketogenic diet
People on keto need more salt

As you cut carbs, I’d recommend you not only add plenty of salt to your food, but also consider supplementing your sodium by drinking some bouillon or broth.  Or simply have a little spoonful of salt once or twice a day, before or after a meal.  You’ll probably feel better if you do!

(Obviously, this advice needs to be adjusted in some individual circumstances, such as people with kidney failure.)

Measure Your Ketones 

Here’s the thing about the ketogenic diet:  

If you don’t have measurable ketones, by definition you’re not eating a ketogenic diet, and you’ll need to make some adjustments.

If you ease into keto as I advised above, don’t expect to see any positive measurements right away.  And that’s fine!

But once you’ve been at it for a month or so, start measuring your ketones.

One cool thing about measuring your ketones is that you can see how you respond to different foods, and ultimately how strict you have to be to stay in ketosis.

For beginners, I’d say start with some cheap urine test strips. They’re not perfect, but they’ll at least give you an idea of whether you’re actually producing ketones or not.  And that’s good enough.

ketone urine test strips
Cheap urine test strips I got from Amazon

After you have a few months under your belt, consider getting a breath ketone meter. Also not perfect, but a little more reliable and less messy than urine.  

(I wouldn’t recommend any beginners go out and get a blood ketone meter– a.k.a fingerstick. That’s because those test strips are super expensive, and it’s not that critical to know the exact measurement.)

After you’ve been doing keto for a few months, you’ll probably be familiar enough that you don’t need to measure your ketones all the time anymore. But at the beginning, measuring your ketones is how you know you’re actually eating a ketogenic diet.  

As a bonus, it can also be really motivating to see the test turn positive.  

Don’t Cheat Too Often

Every time you have a “cheat meal” and kick yourself out of ketosis, it takes a while to get back in. Like 3 or 4 days, on average.

So if you cheat twice a week…. you’re basically never in ketosis, which means you’re not actually “doing keto”. 

Put another way, it’s a lot easier to stay in ketosis than to get back into ketosis.

So if you’re going to do a ketogenic diet, commit to doing it for at least a couple months, and stick with it most of the time! 

Related Questions

To finish up, I’ll try to answer a few common questions. 

Who Should Do Keto, and Who Shouldn’t?

Personally, I think almost everyone (besides babies) should at least try it for a few months.  

By doing a 2-3 month trial, you’ll get a better idea how your body responds, while also giving your pancreas, liver, and other organs a much-needed break from all the sugar.

You’ll also become more “fat-adapted”, which means your metabolism will be more flexible and fasting will become easier.  Win-win!

Obviously, not everyone needs to do keto forever.  Whether that would make sense for you depends on your goals and health status.  

But at least cycling in and out of ketosis from time to time is probably a good idea for just about anyone who wants to optimize their health.

How Long Does it Take to Get Into Ketosis?

Once your carbs are under about 30 grams per day, it usually takes about 3-4 days to have measurable ketones in your urine.

This can vary a lot, but that’s a general rule of thumb.

You might find ketones earlier if you’re using a more sensitive type of measuring device, such as a blood ketone meter.

What Can You Do to Get Into Ketosis More Quickly?

The most efficient way to get into ketosis quickly is to use a combination of strict low-carb,  exercise, and time-restricted eating (TRE).

For example, if you eat close to zero grams of carbs per day, eat within about a 4-8 hour window each day (fairly aggressive TRE), and exercise daily, that’ll substantially accelerate the process.  

You don’t have to be anywhere near that aggressive, and I wouldn’t recommend it when you first start.  But if you’re ever trying to get into ketosis as fast as possible (like after a cheat day), that’s the approach I would take.  

Wait, Isn’t Consuming Fat Terrible for My Health?

Nah.  That’s an old wives’ tale. 😉

There’s a persistent myth that eating fat is bad for your heart, and for your health in general. It’s mostly the result of some misguided dietary guidelines starting in the 1950s and 60s, which still have a strong influence on culture and the media to this day.  Not to mention medical providers.  

I won’t go in-depth here, but if you’d like to understand more about this topic try reading The Big Fat Surprise, or watch Fat Fiction on Amazon Prime.

NoteSome types of fat are clearly harmful, like trans fat, and the oxidized fat in refined vegetable oils.  But that’s because of how they’re processed.  Natural dietary fat is a different story.    

Won’t Eating Fat Make Me Get Fat?


In theory, eating a huge amount of dietary fat could make you get fat. In practice, this almost never happens (at least not in the context of a low-carb diet).

Sure, high-fat foods tend to have more calories. But calories are not the only thing that contributes to weight gain.

A bigger factor in almost every case is insulin (and other hormones).  

When you eat a low-carb, ketogenic diet, your insulin will be low, which makes it easier for you to burn body fat (and harder to store it).  

Eating foods that are high in fat and protein also keeps you satisfied longer, which helps control your appetite. So you may not end up eating as much either. 

Wanna Learn More? 

If that wasn’t enough, and you wanna learn even more about the ketogenic diet, here are a couple good resources to start with.

The video quality is really bad on this interview, but all you actually need is the audio (and it’s available as a podcast as well).  It’s a solid discussion that addresses a lot about the history of the ketogenic diet, various health benefits, and several nuances that I didn’t have time to address in this blog post.  

Ready for a good book?  Check out The Case for Keto, also by Gary Taubes (the guest in the interview above).  

Gary is an investigative journalist who’s been focused on nutritional topics for the past couple decades, and really has a knack for seeing the big picture.

Summary & Final Thoughts

Over the past few years, keto has gotten really trendy. But most people who try it don’t really understand how it works, and often don’t do it effectively.

To do a ketogenic diet, you have to reduce carb intake and increase fat intake until your body starts producing ketones.  You can measure the ketones in your urine, breath, or blood.

Eating a ketogenic diet has a bunch of health benefits, most of which stem from one thing: normalizing blood sugar and insulin levels.

That simple change has a host of secondary benefits, including making it easier to lose weight, improving or reversing diabetes, and lowering your risk of almost every other chronic disease.

The best way to approach a low-carb diet is to ease into it gradually. Reduce your carb intake little by little, one week at a time. That way your body can adapt gradually, and you’ll be less likely to experience unpleasant symptoms, sometimes called “keto flu”.

Most people need to increase their salt intake when they start keto, in order to feel well.  

If you’re serious about doing keto, make a commitment to do it for at least a couple months, and don’t cheat very often (or at all, if possible).  That gives you enough time to adapt, and properly assess your progress.  

Almost anyone would benefit from trying keto for at least a few months. Healthwise, there’s not really any downside to a short trial, and the potential benefits are nothing to sneeze at. 🙂  

Did you find this article helpful? If so, please share it with someone else you know who could benefit!

Share on facebook
Share on twitter
Share on email
Share on print

UPDATE: My podcast is Now LIVE!

Please subscribe on your favorite platform! :)

(You can also just search for “FastingWell” on any app.)


And just in case it helps….

Here’s a link to all the show notes pages, for every episode.

Hope you enjoy it!

Ben Tanner, PA-C

Ben Tanner, PA-C

Ben has been practicing as a physician assistant (PA, or PA-C, similar to a doctor) in emergency medicine, urgent care, and family practice since 2014. Since 2016, he has developed an avid interest in various forms of fasting, using it to improve his own health while helping friends, family, and patients do the same.

Get my "BEGINNER'S GUIDE TO EASY FASTING":