There’s a lot to learn when you first go keto, so I figured hey, why not put all the info in one place?
Without further ado, here are my responses to the questions I get asked most often.
What is keto in the fewest words possible?
“Keto” is any diet where carbohydrate intake is low enough that the liver starts producing ketones (hence the name).
Wait a sec, I thought keto is a high-fat diet? Isn’t eating high fat the point of keto?
Nope. It doesn’t matter how much fat you eat; carb intake is the only criterion that makes a diet ketogenic.
That said, on keto most of your calories do come from fat. You need energy, and when carb intake is very low, the body relies on fat and ketones as its primary energy sources. Still, eating more fat doesn’t make you “more keto.”
What’s the difference between Primal and keto?
Some diets are Primal. Some diets are keto. Some diets are both.
Primal is first and foremost about the types of foods you do and do not eat. The Primal Blueprint doesn’t specifically restrict carbs to a certain level, but it’s naturally low-carb by today’s standards. If you aren’t eating grains, added sugars, or (many) legumes, your carb intake will be considerably lower than the average standard American dieter’s.
Keto diets are agnostic when it comes to food quality. The only thing that technically matters is carb intake. Although many versions of keto do recommend grass-fed meat and organic veggies while avoiding seed oils (very Primal sounding, eh?), it’s also possible to be keto, eating cheap hot dogs and “cheez” out of a can.
Of course, I think the healthiest version of keto is one in which you start out with the Primal Blueprint Food Pyramid and reduce carb intake until you are at ketogenic levels (more on this below).
As much fat as you need to get enough calories and feel satisfied
This is just a starting point. You’ll probably have to tweak your macros to find exactly what works for you. If you do keto for four to six weeks and don’t see any results, try something different. Likewise, if you lose a lot of weight or your goals change, your macros will probably change too.
You might need to start at 30 grams of carbs if you are insulin resistant or have type 2 diabetes.
If you’re very active or building muscle is your primary goal, increase protein up to 1.0 grams per pound of lean body mass.
Don’t rely on food tracking apps to set your macros. Calculate them yourself using absolute amounts (grams), not percentages (e.g., 5% carb, 20% protein, 75% fat).
Do I have to calculate my macros and track my food?
There are people who are perfectly happy doing “lazy keto,” where they eyeball everything and hope for the best. I don’t think it’s the best strategy, especially not if you’re new to all this. Most people don’t have a clue how many carbs are in their breakfast or how much protein they eat in a day.
You have to get your carb intake down to get into ketosis. For your body to stay healthy and fit, you also have to eat enough protein and total calories. Yes, weighing and measuring your food takes time and it sucks some of the joy out of eating. Do it anyway—at least do it for the first week. If you have no problem staying below 50 grams of carbs, and you’re getting enough protein and calories, then you’re good. Stop tracking if you want. If at some point you stop making progress, track your food for a few days again.
Some people subtract the fiber from their carb count because fiber doesn’t significantly affect blood glucose or ketosis. I don’t bother with net carbs because there isn’t a consensus about whether to subtract fiber in all foods or just vegetables. Anyway, people who recommend using net carbs usually limit net carb intake to 20 or 30 grams per day. In practice, that isn’t so different from 50 grams gross (total) if you’re eating mostly whole foods. It’s just another layer of fussiness as far as I’m concerned.
Does fat need to be higher than protein?
In grams, no. However, calories from fat will end up being greater than calories from protein.
Fat has 9 kcal per gram, while protein has only 4 kcal per gram. Even if you were eating 150 grams of protein and 100 grams of fat, that’s only 600 kcal from protein and 900 kcal from fat.
Do I have to limit protein on keto?
The short answer is no. The whole idea that “too much” protein kicks you out of ketosis comes from misunderstanding gluconeogenesis (GNG). GNG is the process whereby your liver makes glucose when your body needs it. (Yes, your body always needs some glucose, even on a keto diet.) GNG is both natural and desirable. Among other things, it ensures the brain always has enough fuel.
The faulty thinking goes like this:
(A) Too much glucose can kick you out of ketosis.
(B) The liver can use certain amino acids from protein to make glucose via GNG.
(C) Therefore too much protein will kick you out of ketosis.
In this case, though, A plus B does not equal C. The liver doesn’t make more glucose than it needs to—it’s a demand-driven process. It’s not going to start dumping huge amounts of glucose into the bloodstream just because you splurged for the tomahawk steak. There are some specific instances in which people doing a therapeutic (medical) ketogenic diet do need to watch their intake. For the average, metabolically healthy person doing keto for general health or weight loss, it’s not a concern.
It’s when people go keto and feel like they got hit by a truck. The most common complaints are wicked headaches and low energy.
Keto flu can last a few days to up to a week, but it’s largely avoidable. First, if you’re eating a high-carb diet, take a few weeks to taper down your carbs. Give your body time to adjust and build some of its fat-burning machinery rather than dive-bombing into ketosis. Second, make sure you up your electrolyte intake as soon as you drop your carbs to ketogenic levels. Insufficient electrolytes are the number one cause of keto flu. Speaking of which…
What’s up with supplementing electrolytes on keto?
One of the first things that happen when you go keto is that your kidneys start excreting sodium. With sodium goes water (which is why people usually see a big drop in the scale at the beginning) and potassium.
You need to supplement these, along with magnesium, especially during the keto transition. Most people continue to supplement as long as they remain keto. You’d be surprised at how often problems like headaches, fatigue, poor workout performance, and mood swings come down to simply needing more electrolytes, especially salt.
If you’re feeling “off” in any way, the first thing to check is electrolytes. Cron-o-meter (and other food tracking apps) will give you that info. You need 3-5 grams of sodium, 1-3.5 grams of potassium, and 300-500 mg of magnesium.
I heard that __[wheat/rice/mangos/beets]__ aren’t allowed on keto. Is that true?
Foods aren’t “keto” or “not keto.” No food will automatically knock you out of ketosis in a single bite.
Of course, the more carbs a food contains, the harder it is to fit into a keto diet. Bananas are tasty and pack a decent amount of potassium, but a medium banana contains 27 grams of carbohydrate—more than half your daily target. Probably not worth it.
A lot of these so-called rules for keto aren’t really about keto per se. They’re about eating a nutrient-dense, anti-inflammatory diet. It makes me chuckle when I hear people say that you shouldn’t have refined seed and vegetable oils like canola and soybean on keto. You shouldn’t have them on any diet. They aren’t un-ketogenic, they’re just terrible, period.
The only accurate way is by using a blood ketone meter. Don’t waste your time on pee strips. They’re not accurate. Most people who do keto for a while find they don’t pee out many ketones, presumably because their bodies are using them. That’s what you want, obviously.
However, I don’t think it’s important for most people who are doing keto for general health and weight loss to measure their ketones. It’s fine to go by subjective assessments. If you have plenty of energy, can delay or skip a meal without getting hangry, and otherwise feel good, do you need to know your blood ketone level? Probably not.
How long does it take to become fat- and keto-adapted?
This is a hard question to answer. It’s not a yes/no thing.
Here’s what we know: Once you drop your carbs to ketogenic levels, it takes about two to three days for your liver to start pumping out ketones. Making ketones is different than using ketones, though. Various studies have shown that it takes at least a couple of weeks for the body to upregulate the “machinery” it needs to burn fat and ketones efficiently for energy. The process continues over several months, as different organs and tissues continue to become better adapted.
The short answer is: Expect it to take a few weeks to start feeling “normal” again after going keto. For people who place a lot of energy demands on their bodies, it will likely take longer. I’ve had endurance athletes tell me it took anywhere from three to six months for their performance and energy to return to baseline. Patience is key.
You never have to start fasting. A lot of keto folks end up fasting intermittently because their appetite is reduced. Fasting also supports ketosis—it’s the ultimate carb restriction. However, it’s also possible to do keto successfully without ever fasting.
If you’re new to keto, I think it’s a good idea to wait a few weeks for your body to adapt before adding the additional challenge of intermittent fasting. Doing an overnight fast of 12 to 14 hours should be no problem, but I wouldn’t go keto and start eating in a 6-hour window at the same time. Your body will struggle to fuel itself.
Once you start, increase your fasting window gradually and pay attention to how your body responds. My general rule is eat W.H.E.N.—when hunger ensues naturally.
I have no energy and my workouts suck all of a sudden. What am I doing wrong?
A few things might be happening here. One, you might not be eating enough food to fuel your activity level. Two, you might need more electrolytes. See the section on supplementing electrolytes above.
Three, you might be working out too hard for how keto-adapted you are. High-intensity workouts are fueled mainly by glycogen (glucose stored in the muscles and, to a lesser degree, liver). When you go keto, glycogen is depleted. Your body is looking to use a fuel that’s not there, at least not in the amounts it needs. That’s why you feel underpowered and draggy.
I recommend scaling back your high-intensity workouts during the transition period. Endurance athletes might also need to shorten their longest training sessions. Even once you’re well adapted, you might continue to struggle depending on how demanding your workouts are. In my experience, keto and hard-core CrossFit don’t mix well, for example. The workouts are just too glycolytic for a lot of people.
You can also try adding back some carbs before or during your hard workouts. It’s called “targeted keto.” I wouldn’t experiment with that for at least the first six weeks, though, to give your body time to adapt.
Weight loss isn’t a guaranteed side effect of going keto, despite how keto is sometimes portrayed. Losing weight can be easier with keto because hunger is usually managed and cravings reduced, but it’s not automatic. You can gain, lose, or maintain weight on keto.
There are lots of reasons why you might not be losing. The most obvious place to start is that you’re eating too much. Yes, calories still matter on keto. Hormones matter too—a lot—but at the end of the day, if you’re eating more energy (calories) than you’re expending, you won’t lose weight.
If you feel pretty confident that your food intake is appropriate for your body and activity level, other variables to consider are:
Sleep and stress: Besides food, these are the two biggest determinants of fat storage or burning.
Movement: Exercise isn’t as important as food intake for weight loss, but it still matters. Too little is bad, but too much can also undermine your efforts by increasing your stress levels.
Medical conditions, hormonal issues. People with hypothyroid issues often find weight loss to be challenging, for example.
Absolutely, lots of keto folks don’t eat dairy. Get your fats from coconut, olive, and avocado products; nuts and nut butters; and canned small, oily fish. Coconut milk can substitute for cream in many recipes.
Can I do keto if I’m a vegetarian/vegan?
It’s very challenging to get adequate protein from non-meat sources and keep carbs below 50 grams per day. If you’re a vegetarian who’s willing to eat eggs, maybe some mollusks, and dairy, you can probably make it work. Vegan keto is possible but extremely difficult. I’m not sure I’d try it.
You can. As I mentioned above, keto is better suited to sports where intensity is kept relatively low—think ultrarunning, for example. The more glycolytic the activity, the more athletes might need to tweak keto to make it work for them.
Of course all athletes benefit from being metabolically flexible. Not to mention, keto athletes frequently report improved body composition and shortened recovery times, likely due to the anti-inflammatory nature of the diet.
My key recommendations for athletes are:
Don’t go keto during periods of heavy training or right before an important competition. Save the Keto Reset for your off season.
Don’t fear carbs. When used strategically and appropriately, there’s no doubt that athletes benefit from some carbs (that doesn’t mean sugary gels). Also, athletes can probably get away with eating more than 50 grams of carbs per day and stay in ketosis. If you want to experiment, invest in a blood ketone meter to find your personal threshold.
If I’m happy with how I’m eating now, do I have to go keto?
Not at all. I’m usually of the “if it ain’t broke, don’t fix it” mindset.
That said, over the past several years I have come to appreciate that keto offers something unique over and above a generally low-carb approach like my typical Primal diet. Keto is the pinnacle of metabolic flexibility. It makes fasting easier if that’s your goal. It seems to have numerous potentially exciting health benefits.
You don’t have to commit to keto long-term. Doing a Keto Reset a couple times a year adds another tool to your metabolic toolbox. If you’re already Primal, dropping your carbs for three to six weeks gives you that added flexibility that you can tap into whenever you need it. Consider it next time you’re bored and looking to shake things up.
Is all this fat I’m eating on keto bad for my heart?
I have been arguing for years, along with many other people in the medical and ancestral health communities, that fat has been unfairly demonized when it comes to heart health. Neither dietary fat nor dietary cholesterol is the villain when it comes to cardiovascular disease risk and mortality. Instead, we should be looking first at chronic inflammation from the Standard American Diet (SAD), chronic stress, and other lifestyle and environmental factors.
There is abundant evidence to support that position, but let me just drop two recent meta-analyses here:
This one concluded that, in fact, low-carb diets have a beneficial effect on cardiovascular risk factors.
And this one that found that the only risk factor for cardiovascular disease was consuming more trans fats. Otherwise, fat intake was unrelated to heart disease.
My cholesterol went up on keto. Is this dangerous?
I’m not your doctor. I don’t know what’s “dangerous” for you. However, I’m also on record as being highly skeptical of the traditional lipid hypothesis of heart disease. I’m not at all convinced that “high” cholesterol is always bad, nor that lowering cholesterol is always desirable.
Anecdotally, many people do find that their LDL and total cholesterol go up in the first few months of keto. It makes sense. Lipoproteins—as in low-density lipoproteins (LDL) and high-density lipoproteins (HDL)—transport fat in the bloodstream. It’s not there to cause trouble, it’s there to do a job.
In studies, keto diets have been shown over and over and over to result in more favorable lipid profiles—lower triglycerides, higher HDL, and more favorable HDL:TG ratios—over time, compared to low-fat diets. Many people also find that LDL decreases, although this varies from person to person.
If your cholesterol really skyrockets and stays high after several months of keto, you might be a hyper-responder. The jury is still out on whether it’s safe to continue with keto if this is the case. Talk to your doctor and consider going back to a more low-to-moderate-carb Primal diet.
People hear “fatty liver” and assume that it is caused by eating too much fat. In fact, non-alcoholic fatty liver disease is related to hyperglycemia (high blood sugar), insulin resistance, and metabolic syndrome—all things related to eating too many carbs. Keto is known to reduce each of those risk factors.
Can I do keto without a gallbladder?
Probably yes. You might need to supplement with ox bile salts.
Can I have alcohol on keto?
You can, although you’re likely to get knocked out of ketosis temporarily. If being in ketosis 24/7 is important to you, I wouldn’t risk it.
If you decide to imbibe, opt for dry wines, champagne, or clear spirits with non-sugary mixers. Most people find that they are much more sensitive to alcohol on keto, so be careful. That third glass of wine might find you dancing on the table.
Should I buy this keto supplement? My neighbor swears it helped her lose 15 pounds.
Listen, I’m not opposed to exogenous ketones in certain circumstances (that’s ketones you take as a supplement, as opposed to ketones your liver produces). However, weight loss never comes in a bottle. Eat well, move, sleep, manage stress.
There’s no “should” here. You can stay keto as long as you want, provided you continue to feel good and like how you’re eating. Try to stick to strict keto for six weeks at least before adding carbs back in if that’s what you decide to do.
First, don’t panic. There are a few possibilities here. One is telogen effluvium, the apparently harmless and temporary hair loss that can follow any major stressor, dietary change, or significant weight loss. It usually manifests around three months after the stressful event/period. There’s nothing that needs to be done about telogen effluvium. Support yourself as always with a generally healthy diet and lifestyle, and your hair will return on its own.
Hair loss can also be caused by dietary factors, especially not getting sufficient protein or B vitamins, or not eating enough calories overall. Try tracking your food for a week and see where you are with those.
Finally, hair loss can be a symptom of thyroid issues. If you are also experiencing any other troubling or mysterious symptoms, see your doctor.
One last thing you should know about going keto: If you are on any prescription meds, make sure your doctor knows about your plan. Certain medications will need to be adjusted as you become more insulin sensitive, lose weight, or otherwise improve your health. In particular, if you use insulin to manage type 2 diabetes, your dose might change within the first few weeks of keto.
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.