There are so many different sites that answer this question that I almost didn’t write this article. However, I get the question anyway, so here are the basics…
- Meat (beef, chicken, seafood, fish)
- Specific fruits (berries, avocado, and olives)
- Specific dairy (cheese, cream, sour cream, and cream cheese)
- Fats and oils
- Non-starchy vegetables
- Nuts and seeds
- Unsweetened / diet drinks
- Fiber based foods like Shirataki (glucomannan) noodles / rice
Meat (beef, chicken, seafood, fish)
From a carbohydrate standpoint, beef, chicken, fish and most seafood is considered “free” food. Some shellfish have low levels of carbohydrates, but most meat is carb-free. However, because high amounts of protein may limit ketosis (see “How do you stay in ketosis?”), it is important to make sure you are not eating too much, especially compared to your fat intake. The formula to make sure any particular meal is ketogenic is as follows:
FAT GRAMS ÷ (PROTEIN GRAMS + NET CARBS GRAMS)
Add the number of protein grams and the number of net carbs (see “What are Net Carbs and why do they matter?”). Divide the number of fat grams by this number and you will get the ketogenic index.
Any answer greater than 1 is good. Anything less than 1 is questionable, with it getting worse as the number gets lower. This way of looking at food may be a little advanced for keto beginners, but if you stay on the diet, this will be the best way to make sure you are getting enough fat for optimal weight loss.
It is also important to eat a variety of meats so you can get different nutrients, not to mention keeping you from getting bored with options. Grass-fed animal meat is preferable to grain fed animals, as the meat contains higher amounts of omega-3 fatty acids, antioxidants and various other nutrients. Fatty fish, like salmon, mackerel, seabass and trout are also good for omega-3 fats. Uncured bacon is another great keto meat. Its ratio is just over 1:1, which is ideal for a ketogenic diet.
Eggs are another form of protein that is very keto friendly. Each large egg contains less than 1 gram of carbs, around 6 grams of protein, and 5 grams of fat. They are pretty close to ideal in regards to the ketogenic index, although not quite as ketogenic as bacon. However, they contain other nutrients that bacon doesn’t.
Specific fruits (berries, avocado, and olives)
Certain fruits, primarily berries, are also keto friendly, keeping in mind portion control. Raspberries and blackberries are the best, followed closely by strawberries.
Avocados are also technically berries, even though we don’t really think of them as such. One entire medium avocado (around 200 grams) only has around 4 net carbs, 4 grams of protein and 30 grams of fat. That is a ketogenic index of 3.75! By far one of the best keto foods to keep available in your kitchen.
Olives are also a good keto fruit, although black olives have a higher carb count than green olives. Black olives ketogenic index is just over 3 and for green olives it is over 7! That is an amazing index.
Specific dairy (cheese, cream, sour cream, and cream cheese)
Dairy can also be keto friendly, although you have to be careful with shredded cheese. Check the labels carefully because many companies add maltodextrin, which is anti-ketogenic. It is always best to shred your own cheese as needed.
Most cheeses are ketogenic and keto friendly. For example, cheddar has a ketogenic index of ~1.25, whereas provolone is just under 1. Hard cheeses like cheddar, swiss and parmesan also have less lactose, which is the main carbohydrate for dairy products, so they make good keto ingredients.
Again, watch the protein content too, as some cheeses have more protein than fat, like mozzarella. Not to say you should avoid mozzarella, only to keep in mind that mozzarella and other high-protein cheeses should probably be eaten with other fats to increase their ratio.
Cream, heavy whipping cream and butter are all high-fat dairy products that are very low in carbs. All are nearly “free” foods, due to the higher fat content. Sour cream is another dairy product that is a staple of the keto diet with a ketogenic index of ~4, as is cream cheese with an index of ~3.33. As with all keto foods, always read the nutrition facts label.
Fats and Oils
Although not all fats and oils are the same, they are almost all “free” ketogenic foods. Olive oil and coconut oil are the two most often discussed oils on the keto diet, but in terms of ketogenic index, they are all acceptable.
However, this is only a ketogenic diet discussion, not a “which oils is healthiest” discussion, nor are all oils equal when it comes to cooking temperature, but that is beyond the scope of this post. Basically, all fats are good from a ketosis point of view.
The one real difference is with MCT oil, or medium chain triglyceride oil. Most MCT oil on the market is a derivative of coconut oil or palm kernel oil, although many are now focused on caprylic acid, or C8, as a stand-alone MCT. That is because caprylic acid is more ketogenic than the longer MCTs (C10 and C12) or even the shorter C6 MCT.
MCT is awesome for ketogenic diets for multiple reasons. First, they are easier to digest, so they get absorbed easier than other fats. They don’t require “packaging” to move across the intestinal wall like larger fats and do not require bile, pancreatic enzymes or carnitine like long chain triglycerides do.
The other great thing about MCT oil is that it is less likely to be stored as adipose tissue (body fat) when there is an excess of fat calories in the system. However, they do NOT contain essential fatty acids (those required by people, but not made by the body), so MCT oil cannot replace all of the fat in your diet. Additionally, they can cause GI upset, although this decreases with time.
There are all kinds of infographics and lists that identify the best vegetables for ketogenic diets, so I won’t go into all of them here. The most important concept to remember is that if what you are eating was once underground, it is probably not good for keto. Think potatoes, carrots, or other root vegetables. There are exceptions, like radishes and to a lesser extent, turnips, but if it grows underground, it is probably too many carbs for keto.
Raw leafy vegetables are almost all low carb, although those carbs can get concentrated when cooked, so keep them raw when possible. A quick example is raw spinach is around 1.1 gram of carbs per cup, but that goes up to 6.8 grams per cup after being cooked. Quite a big difference.
Stem vegetables have a little more carbs than leaf vegetables, although most are still keto friendly. Cauliflower, broccoli and celery are all good examples of keto staples. The difference between these and leaf vegetables are that stem vegetables’ carb levels actually drop with cooking, so they are best when not eaten raw.
Seed vegetables are the last major vegetable group that is keto friendly. You have to be a little careful with them, as some have more carbs than others. Cucumbers and zucchini are probably the most consumed seed vegetables in keto diets, followed by bell peppers (or other peppers for that matter).
Mushrooms, although not even a vegetable, are also good for keto diets. They too increase in carb count when cooked, but they remain low enough to be keto friendly. Plus, they are a good source of vitamins, minerals and dietary fiber. Again, it is important to eat a variety of low-carb vegetables so you can get adequate nutrition.
Nuts and Seeds
Nuts and seeds are high-fat, low-carb, high-fiber protein sources. Cashews and pistachios have the highest net carbs in the nuts category, so should be eaten in moderation, while pecans and macadamia nuts are two of the lowest and are virtually “free”.
It should be noted that nuts and seeds are very dense, so all of them should be eaten in portions as to not overdo it. Too much of anything can be bad.
Unsweetened / diet drinks
Unsweetened drinks, like black coffee and teas, are “free” on keto. The same goes for diet drinks as long as the sweeteners used are keto friendly. However, this is only a ketosis discussion and we understand that many people on ketogenic diets want to avoid chemicals and artificial sweeteners. For these dieters, natural alternatives are better and some major US brands are now making Stevia-based diet drinks and other naturally sugar-free sweeteners.
Fiber based foods
On final category, although I hesitate to actually call it food, is fiber-based. These are foods made from things like chicory root or glucomannan. The latter is particularly interesting as the fiber can be made into noodle or rice shapes. Shirataki (glucomannan) noodles are clear noodles composed primarily of water that can be used to replace pastas and rice. They obviously don’t taste the same, but the texture is somewhat similar and they tend to absorb the flavor of whatever they are cooked with.
The great thing about them is that they are almost calorie free, they provide bulk to meals, supply dietary fiber, and help you feel full longer. Additionally, it can help slow down digestion, limiting post-prandial blood glucose levels (which also lowers insulin), thus making it ketogenic as well. All around, a great addition to any keto pantry.
There are a lot of keto food blogs and keto recipe blogs that will go into further details about what is best to eat on keto, but I hope this introduction sets you on the right path. Very few websites discuss ketogenic index foods though, so if you learn nothing else from this post, please remember that.
Also, remember that a lot of diet food manufacturers use labels as a marketing ploy, so statements like “sugar-free” and “no sugar added” should be assumed to be marketing statements, and you have to read the label to verify they didn’t sneak carbs into the product.
In fact, some of the larger keto food brands that make meals and snacks specifically for ketogenic diets are not ketogenically friendly at all. See “What are Net Carbs and why do they matter?” for a further discussion of this, sugar alcohols and glycemic index. You need to be informed or you may eat something “keto-friendly” that kicks you out of ketosis.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.