This guide is for anyone new to a low-carb high-fat diet or a ketogenic diet. If you’re wondering how to begin, this guide will provide all of the necessary information to get started, including an explanation of a low carb diet and related terms, reasons why it can be beneficial for your health, how to read nutrition labels and calculate net carbs, how to track your foods, and what you can eat and what to avoid.
Preparation is key — without it, this lifestyle transition may be unnecessarily difficult or confusing. This guide will provide all of the information you need in one place so that you can get started quickly.
- A ketogenic diet restricts carbohydrate intake sufficiently enough to cause ketosis, which occurs when your body burns fat instead of glucose as its primary energy source.
- Science studies show that a low carb diet improves cardiovascular health and is effective for weight loss and type 2 diabetes compared to other diets.
- Net carbs is calculated as total carbs minus fiber, and represents the amount of carbs digested by your body. Staying under 20-50 g per day is recommended to be in ketosis.
- Track all of your foods and drinks in a log so that you can count how many net carbs you’ve consumed daily.
- Low carb foods include all meats and seafood, most dairy ingredients such as heavy cream and cheese, some vegetables like broccoli and cauliflower, and some nuts like almonds and macadamia nuts.
- Drink plenty of water and increase consumption of foods high in electrolytes (potassium, magnesium, and sodium), which also helps with the “keto flu.”
Jump to section:
- What is a low carb or keto diet? What is ketosis?
- Why should I follow a low carb diet?
- How do I read nutrition labels? What are net carbs and macros?
- How many daily net carbs, protein, fat, and calories can I consume?
- How do I log and track what I’m eating?
- What foods am I allowed to eat? What should I buy at the grocery store?
- What is the “keto flu”? How do I get enough water, electrolytes, and fiber?
- Can I follow this diet if I have an irregular schedule? What is intermittent fasting?
- When is the best time to start this diet?
What is a low carb or keto diet? What is ketosis?
A low carbohydrate (“low carb”) diet is one that restricts consumption of carbohydrates. Some of these low carb diets are ketogenic (“keto”) diets because they restrict carb intake enough to cause ketosis — for instance, the Atkins diet’s induction phase is considered a ketogenic diet.
There is no strict threshold for a diet to be considered “low carb.” Some consider a low carb diet to be one where daily carb intake is between 50 – 150 g, which is above the level where most people will generate sufficient ketones, and a very low carb diet or ketogenic diet to be one where daily carb intake is below 50 g.
Due to carb restriction, the body will have low glucose availability, which also happens during fasting. The body responds to this by increasing production of ketones, which are converted from fatty acids in the liver. Ketones are released into the blood, traveling to the brain and other tissues. These ketones replace glucose as the dominant source of energy.
When there is a sufficient level of ketones in your blood, the body is in a state called ketosis, which is also an effective way of treating difficult epilepsy in children. For most people, the maximum allowable amount of daily carbs is 20 – 50 g in order to stay in ketosis. Since carbs are highly restricted, the keto diet is considered a low carb, high fat, and moderate protein diet.
To figure out if your body is in ketosis, you can use breathalyzers to measure acetone, one of the three ketone bodies (others are acetoacetate and beta-hydroxybutyrate). The downside of breathalyzers is that they can produce inconsistent results, and are dependent on the manner in which you exhale into them. Urine test strips can measure acetoacetate, but this tends to correlate poorly with blood ketone levels. Lastly, finger-stick ketone meters can provide beta-hydroxybutyrate levels in the blood. Personally, I prefer tracking my daily carb intake to determine if I am in ketosis as opposed to relying on ketone measurements.
Even though your body may be in nutritional ketosis in a matter of days (as glycogen and blood glucose reserves are depleted), it may take weeks to months to become fully keto adapted.
Note that the body’s acid-base homeostasis is maintained in ketosis, which is different from ketoacidosis, a medical emergency where there is uncontrolled ketone production and usually the result of complete insulin deficiency in type 1 or late-stage type 2 diabetics.
Why should I follow a low carb diet?
Before starting this diet, consider your motivations and reasons for doing so. For many people, it’s about weight loss. For others, it may be about managing their diabetes. Ask your primary care physician if you have any questions on whether or not this diet is right for your specific situation.
To understand why a diet low in carbohydrates can be beneficial for your health, I recommend going straight to the source — scientific papers with human trials published in peer reviewed journals. I’ve compiled a growing list of papers with short summaries of their main findings.
Your first task is to take a look at these papers to understand why a low carb diet is well supported by numerous scientific studies. These papers are also excellent material for sharing with friends and family members who are unsupportive of your decision to try this diet. And check out this article addressing some common concerns about low carb diets.
How do I read nutrition labels? What are net carbs and macros?
When you’re just starting out on a low carb diet, you’ll want to diligently read the nutrition label of every product at the grocery store before buying it. This is especially true at the beginning when you don’t yet have a good grasp of which foods have carbs and which don’t. For example, did you know that just 1 tablespoon of lemon juice has 1 g of carbs? Or that even dried spices have carbs?
These things add up, and so you’ll need to know what is in all of your foods so that you don’t go over your daily net carb limit. Almost everything has some amount of carbs, unless they’re pure fats (such as oils) or protein. Moreover, different brands of the same foods can vary wildly in their carb counts, so always check the nutrition label beforehand.
In American nutrition facts labels, total carbohydrates are provided, as well as a breakdown into sugar and fiber categories. Net carbohydrates are the relevant quantity for us because they represent the carbs that can be digested by the body. Net carbs are calculated as total carbs minus fiber. In cases where non-digestible sugar alcohols such as erythritol are used, net carbs are defined as total carbs minus fiber minus erythritol:
Net Carbs = Total Carbs – Fiber – Sugar Alcohols (e.g., erythritol)
Since net carbs represent what the body can digest, I always use net carbs when calculating how many grams of carbs I’ve eaten. Whenever I mention carbs on this site, I am referring to net carbs. When you read a nutrition label, you should mentally calculate the total carbs minus fiber to figure out how many net carbs are in each serving.
Also, pay attention to the serving size listed on the nutrition facts label. A product may only have 0.5 g net carbs per serving, but if each serving is only 1 tablespoon and you need a whole cup, then you need to account for it.
The next step is to gain an awareness of how many net carbs are in typical foods. Check the nutrition facts labels of products that you currently have in your pantry and refrigerator. What foods surprised you? Next time you are in the grocery store, check the labels of some items to gain an understanding of the kind of foods that are high in carbs.
Another term that you’ll hear often is macronutrients (“macros”). There are three primary macros in food that provide energy to our bodies: fat, carbs, and protein. In a low carb diet, you’ll be eating a lot more fat and protein to make up for the loss in carbs. Some people like to set daily macro goals and track their macros every day, beyond just tracking net carbs. If that’s you, read on to the next section on how to set daily goals.
How many daily net carbs, protein, fat, and calories can I consume?
There is no single way to follow a low carb diet. Some people stick to a strict under-20 g net carbs per day, for others that number may be 30 or 50 g. Some people don’t count carbs at all and simply avoid sugars and refined carbs. If you find yourself not seeing any results (e.g., weight loss), then I highly recommend tracking your daily net carbs and calories to identify the issue. To keep yourself in ketosis, staying under 20 g is the surest way, but it’s usually possible to stay in ketosis when limiting yourself anywhere from 20 g to 50 g a day.
Pick a daily net carb limit that is feasible for your lifestyle. If 20 g doesn’t work for you, then pick a higher limit. Some people start off with a 20 g daily limit, and then slowly work their way up by adding 5 g to their daily limit each week. Do what works for you, as there is no one-size-fits-all approach to a low carb lifestyle.
Beyond net carbs, you can also do the same for other macros such as protein and fat, as well as calories. Protein is a goal; you should make sure your foods give you enough protein each day. Once you hit your protein goal, there’s no need to consume more — this is not a high protein diet. And fats are for the purpose of keeping you full. You can also set a calorie limit, especially if you’re trying to lose weight.
There are a variety of online keto macro calculators that tell you how many carbs, protein, fat, and calories you should be consuming each day. Remember: protein is a goal, carbs is a restriction, and fat is what you eat to keep yourself satiated. That’s why this diet is considered low carb, high fat, and moderate protein.
If being in deep ketosis is important to you, it’s helpful to examine the percentage of calories coming from fat. A 4:1 fat ratio in terms of energy (i.e., 80% of calories coming from fat, 20% from everything else) is a good rule-of-thumb. That roughly corresponds to a 2:1 ratio in units of weight.
How do I log and track what I’m eating?
You should track all of the food that you eat throughout the day so you know how many net carbs you’ve consumed. There are a variety of ways you can do this.
You can use an app like myfitnesspal, which has a large nutrition database and a food diary feature to log your meals. You can use their app to scan barcodes of products, which will be automatically added to your log without having to manually enter macros. My favorite one is Cronometer, which tracks over 70 nutrients (helpful to see if you’re deficient on anything) and all of their nutrition facts are accurate, since they don’t rely on user-submitted data. They have nice features like time stamps on when foods were eaten and custom graphs. If you prefer automatic meal planning features such as food suggestions that meet your macro targets, check out Eat This Much.
If you don’t like the idea of using an app, you can use a simple text file or take a pen-and-paper approach. In the past, I have used a Google spreadsheet to log my food and track my carb totals as well as an Airtable database, which is synced across all of my devices.
I recommend starting a food log today so that you can start making it a habit as soon as possible. You don’t need to wait until the day you plan to start a low carb diet. Remember to track everything, even creamers that you put in your coffee. Tip: add the food to your log before eating it, so you don’t accidentally go over your daily carb limit.
Some people count and track calories, and some prefer a more relaxed approach. My suggestion is to skip calorie counting for at least the first week or two of the diet, as you’re still getting adjusted to this new way of eating. Just eat when you’re hungry. Afterwards, if you think calorie counting is both doable and useful for your goals, you can add that to your logs.
I also highly recommend buying a food scale if you don’t have one already. A food scale will help you get a weight estimate of your serving sizes, which will make your food logging and tracking much more accurate. You can get one on Amazon for less than $20.
What foods am I allowed to eat? What should I buy at the grocery store?
Strictly speaking, there are no forbidden foods on a low carb diet; as long as something fits your macro goals (e.g., under your daily carb limit) then it is allowed. Your body will produce ketones when glucose availability is low, and doesn’t discriminate if the glucose came from carrots or broccoli. However, there are definitely some foods that are more amenable to a low carb diet than others because they are naturally very low in carbs.
Here are some common low carb foods:
- Cruciferous vegetables, like broccoli, cabbage, cauliflower, and brussels sprouts
- Leafy greens, like kale and spinach
- Any kind of protein, like seafood, pork, chicken, beef, and turkey
- Eggs and high fat dairy items, including heavy whipping cream (watch out for hidden carbs), butter, and most kinds of cheeses
- Snacks like roasted flavored almonds, macadamia nuts, pumpkin seeds, and olives
- Basic cooking and baking ingredients, including cooking oils, vinegars, mustard, mayonnaise, almond flour, coconut flour, and dried spices
I’ve compiled a list of low carb grocery items, organized by section such as fresh produce, meat, and dairy. Bookmark that page so you can start buying healthier ingredients next time you’re at the store.
Are you a home cook? If you enjoy making new dishes, visit my Recipes Homepage, which has categories of recipes organized by course. All of these recipes have nutrition facts labels. I also recommend subscribing to my free e-mail list to get notifications of recipes that you may enjoy.
Are you an online shopper? Check out my curated list of Amazon products, which includes some of my favorite low carb snacks and baking ingredients.
Don’t cook? You can supplement some of your calories with meal replacement options, which include powders and ready-to-drink shakes with vitamins and minerals. Here’s a fantastic spreadsheet with comparison between meal replacement brands including cost, net carbs, calories, and flavors. My favorite is Keto Chow because they have a wide variety of flavors, mixes smoothly without clumps, and has no added MCT oil (which my body doesn’t tolerate well). Keto Fuel is another good choice; it’s more affordable but contains MCT oil, has fewer flavor options, and a grainier taste.
What is the “keto flu”? How do I get enough water, electrolytes, and fiber?
Low carb diets can have a diuretic effect, which means you’ll lose more fluids and minerals through increased urine production. If you aren’t getting enough water and electrolytes (including potassium, sodium, and magnesium), you might experience “keto flu” symptoms such as dizziness, headaches, fatigue, and muscle cramps (more side effects). Also, when you switch to a low carb diet, you might find yourself consuming less sodium because carb-heavy meals tend to use a lot of salt.
Water: Consider drinking at least 2-3 liters of water daily. Personally, I’ve tracked my daily water intake by using a 2-liter jug. I fill up the jug twice a day, and I need to finish all of it by the end of the day. To make water more palatable, you can make tea, add sugar-free flavored powders, or add a squeeze of Mio.
Magnesium: Take a daily supplement. I take a 400 mg capsule of triple magnesium complex that provides magnesium in the form of magnesium oxide, magnesium citrate, and magnesium aspartate. You can buy this online or find it at your local drug store. Note that some magnesium supplements may have a laxative effect on you, which could be desirable or not. This page explains the different kinds of magnesium.
Potassium: This can be supplemented by taking LoSalt (or Morton’s LiteSalt), which is reduced-sodium salt that has more potassium than you can find in potassium supplements. You can season your foods with LoSalt, or you can add a small amount to your drinks throughout the day. Each 1/4 teaspoon serving of LoSalt provides 450 mg of potassium, whereas potassium supplements are limited by the FDA to less than 100 mg.
Sodium: You can generously salt your foods, or use bouillon cubes, which are small cubes of dehydrated vegetables, sodium, and seasonings that are combined with hot water to drink. These cubes contain about 2 g of sodium each. If you’re worried about consuming too much salt, note that salt restriction recommendations actually lack credible evidence.
Many people on a low carb diet notice that they have fewer bowel movements than before. Some find this to be convenient, and others find it disconcerting. If you would prefer to use the bathroom more regularly, consider adding more fiber to your diet.
Here are some low carb foods with plenty of fiber:
- 1 avocado has 52% daily recommended fiber
- 1 cup almonds has 44% daily recommended fiber
- 1 head of cauliflower has 48% daily recommended fiber
- manufactured low carb protein bars like Quest or Costco’s Kirkland bars — these have about 50-60% daily recommended fiber
Before you start this diet, make a mental note of how you plan to take your electrolytes. Buy the necessary supplements, bouillon cubes, etc. next time you are shopping.
Can I follow this diet if I have an irregular schedule? What is intermittent fasting?
Absolutely. If your job has an odd schedule or demanding hours that prevent you from bringing and eating low carb foods at work, you can simply fast while you are at work and eat when you are at home.
This is called intermittent fasting, which means a cycle of fasting and non-fasting. Some people fast for 16 hours and only eat in an 8 hour window (e.g., eating from 12:00 pm to 8:00 pm). Others only eat every other day. Note that the “sweet spot” is at least 18 hours of fasting — that’s when you see a substantial drop in insulin and increase in fat breakdown.
You can do whatever cycle that fits your current schedule and is convenient for you. Fasting has many benefits, including improved cardiovascular health, better mental acuity, and higher insulin sensitivity.
Breakfast is not necessary. You can certainly eat breakfast if you’re hungry at that time, but you should not force yourself to eat breakfast if you’re not hungry. People who eat breakfast tend to overeat every day by an extra 500 calories.
In summary, it’s better to eat meals during a shorter fraction of the day rather than spreading your meals throughout the day (snacking or grazing), to allow your body a significant period of time in which it is insulin deficient.
When is the best time to start this diet?
The next step is to pick a start date. The sooner you can start this diet, the sooner you can start reaping the benefits. However, it’s better to start this diet when you have access to your own kitchen and are able to prepare your own foods. If you plan to travel soon for the holidays or you have a vacation coming up, it’s best to wait until after you return, as it can be challenging to find appropriate foods while traveling.
Once you’ve picked a start date, you should plan to rid your pantry of all high carb products that will tempt you. Either move the products to a higher shelf, give them away to other people, or throw them away. The same goes for anything in your refrigerator. Plan ahead so that anything high in carbs will either be gone or consumed by the time you plan to start this diet.
If you have any questions, please let me know in the comments below.