Diets we support › Keto

How it works

You build meals around fat and protein: meat, fish, eggs, cheese, avocado, and oils, with plenty of low-carb vegetables. Starchy foods, sugar, and most fruit stay very limited. Carbs are restricted enough that planning really matters, and that's where a done-for-you plan earns its keep.

How to read the carbs: what "net carbs" means

On keto, the number that matters is net carbs, not total carbs. Net carbs are just the total carbohydrate with the fiber taken back out:

Net carbs = Total Carbohydrate − Dietary Fiber

Fiber is a carbohydrate your body doesn't digest or absorb, so it doesn't raise blood sugar or pull you out of ketosis. That's exactly why keto subtracts it out. So don't be thrown if a recipe's Nutrition Facts label shows, say, 2 g total carbohydrate and 2 g dietary fiber but the recipe counts as 0 g net carbs: those 2 grams are all fiber, and fiber doesn't count against you. It's not a mistake. The label uses the standard government format, which always lists total carbs and fiber separately, and we show the net-carb number right alongside it so you can plan your day the keto way.

Where keto comes from, and who it helps medically

Keto didn't start as a weight-loss trend. Doctors developed it back in the 1920s to treat epilepsy, and it's still prescribed for that today. Children whose seizures don't respond to medication often do remarkably well on it, and it's a first-line treatment for a few rare genetic conditions like GLUT1 deficiency and pyruvate dehydrogenase deficiency. In those cases the body can't use glucose the normal way, so running on ketones instead is what keeps things working. It's always closely supervised by a doctor.

Most of what we've learned since then is about metabolism, which is where keto overlaps with the conditions we plan around. Cutting carbs this far does steady blood sugar and insulin, and that shows up in the research on type 2 diabetes and blood sugar and fatty liver. For PMOS, which used to be called PCOS, the international guideline is honest that no single eating pattern has proven better than the others, so keto is one reasonable option there rather than the answer.

Here's the part that usually gets left out. Keto's advantage is mostly early. In head-to-head trials it pulls ahead in the first six months, and by twelve months the difference between keto and other approaches has largely closed. The British review that looked at blood sugar found no difference in HbA1c by two years. That isn't a reason to skip keto, and it isn't a failure on your part if it happens to you. It's the same pattern almost every diet shows, and it means the question worth asking on day one is not how fast this works but whether you can picture eating this way in a year.

You'll also see keto studied for migraines, for Alzheimer's and Parkinson's, and lately for mental health. That work is early and nowhere near settled, so I'd treat it as a reason to ask your doctor, not a promise. Whenever keto is being used for a medical reason, it should be something you do with your care team. We handle the food; we don't replace your doctor.

Get your cholesterol checked, before and after

This is the one thing I ask of anyone starting keto, and it's the piece most keto guides skip entirely. When you build a way of eating around fat, your cholesterol can move, and it doesn't move the same way for everybody. For most people the change is small. For a minority it isn't. There are people in the research whose LDL more than doubled on keto, and the ones it happens to are not who you'd guess.

The bigger rises tend to show up in people who are lean and under fifty, which is very often exactly who is drawn to keto in the first place. Being slim and feeling great is not evidence that your lipids are fine. The only way to know is to look.

If your numbers are steady, you have an answer and you can stop wondering. Either way you'll know, which beats guessing for a year.

Who should be careful, or skip keto

Keto is a big metabolic change, and it isn't right for everyone. For a few people it's simply not safe, and for others it's fine only with a doctor watching closely. Please don't do keto if any of these apply to you:

• You have a rare inherited problem with fat metabolism, such as a fatty-acid oxidation defect, a carnitine deficiency, pyruvate carboxylase deficiency, or porphyria. The body can't safely burn fat for fuel in these, and they're usually caught in childhood.
• You take an SGLT2-inhibitor for diabetes (empagliflozin, dapagliflozin, canagliflozin and the like). Together with keto, these can bring on a serious ketoacidosis even when your blood sugar looks normal.
• You have pancreatitis or real trouble digesting fat.
• You are pregnant. Pregnancy needs a carbohydrate floor of its own, and ketosis in pregnancy is a signal to act on rather than a goal. If you were eating keto before you conceived, talk to your provider about coming off it rather than carrying on.

And a few people can do keto, but only with a doctor keeping an eye on things. Check in first if you:

• Have type 1 diabetes, or use insulin or a sulfonylurea. Your doses will usually need to change.
• Don't have a gallbladder, or have ongoing gallbladder trouble.
• Have advanced liver or kidney disease.
• Have a history of disordered eating, since a strict plan can pull old habits back.

If any of that sounds like you, talk it over with your doctor before you start. And if keto turns out not to be the fit, a steadier blood-sugar plan or a Mediterranean one will get you a lot of the same benefit with fewer strings attached.

Common questions