The difference in keto vs low carb comes down to how far you cut carbohydrate and what replaces it. A low-carb diet, as Diabetes UK describes it, generally means eating fewer than 130g of carbohydrate a day. A ketogenic, or keto, diet goes much further, typically below 50g a day and sometimes as low as 20g, and deliberately makes fat the main source of energy so that the body produces ketones. All keto diets are low-carb, but most low-carb diets are not keto.
Key takeaways
- Low-carb generally means under 130g of carbohydrate a day; keto is usually under 50g.
- Keto is high in fat by design, with protein kept moderate.
- Keto rules out grains, sugar, most fruit and legumes; low-carb leaves room for some.
- Both need medical advice first if you take insulin or medicines that can cause hypos.
Keto vs low carb at a glance
| Low-carb | Keto (ketogenic) | |
|---|---|---|
| Typical carbohydrate limit | Under 130g a day | Under 50g a day, sometimes 20g |
| Main goal | Reduce carbohydrate, especially refined starches and sugars | Reach ketosis, where the body uses ketones for fuel |
| Fat | Not set; often moderate | High: commonly 70 to 80% of daily calories |
| Protein | Not set | Moderate: commonly 10 to 20% of calories |
| Fruit | Whole fruit can fit | Mostly excluded except small portions of berries |
| Pulses and whole grains | Can be included as high-fibre carbs | Excluded |
| Flexibility when eating out | High: swap the starchy side | Lower: sauces, vegetables and drinks all count |
The low-carb figures come from Diabetes UK’s guide to low-carb eating, which describes low-carb as reducing your daily total to less than 130g. The keto figures come from the Harvard T.H. Chan School of Public Health’s review of the ketogenic diet, which says the diet typically reduces carbohydrate to less than 50g a day and that popular resources suggest an average of 70 to 80% of calories from fat, 5 to 10% from carbohydrate and 10 to 20% from protein.
What makes keto different
Keto is defined by ketosis. Harvard’s review explains that when carbohydrate is scarce, the liver makes ketone bodies from fat, and when they build up in the blood this is called ketosis. Getting there and staying there requires keeping carbohydrate very low and fat high at every meal.
That is a different goal from general low-carb eating, which is mainly about cutting back on starches and sugars. Diabetes UK, for example, suggests that the carbohydrate you do eat comes from high-fibre foods such as pulses, nuts, vegetables, whole fruit and whole grains. On a strict keto plan, Harvard notes that grains, flour products, added and natural sugars, legumes and most fruit are all excluded.
What it means for ordering in a restaurant
On a low-carb plan, most menus work with one or two adjustments: swap chips or rice for vegetables, choose a protein-led main and skip the sugary drink. Our guide to low-carb ordering at restaurants sets out that method step by step.
Keto asks more. Because the daily limit is so much lower, things that barely matter on a low-carb plan start to count:
- sweet glazes, ketchup-style sauces and some dressings
- starchy vegetables such as potatoes, sweetcorn and parsnips
- beans and lentils in stews and salads
- most fruit-based desserts and many drinks
In practice, keto diners tend to order plain grilled meat or fish with green vegetables, eggs, cheese or salads with oil-based dressings. Steakhouses and grills are often the easiest places to eat. Asking for dressings and sauces on the side gives you control over how much you use, and asking what the “seasonal vegetables” are today avoids a surprise portion of potatoes. Keto is not the same as gluten-free, either: cutting out flour products does not protect against crumbs from shared equipment, which our guide to eating out with coeliac disease explains.
Health points to weigh
Both approaches need care if you manage a medical condition. Diabetes UK advises anyone taking insulin or other medicines that can cause hypos to speak to their healthcare team before going low-carb, and notes that some people taking SGLT2 inhibitors may need to stop them because of the risk of diabetic ketoacidosis. It also says low-carb diets should not be recommended for children.
Harvard’s review lists possible short-term side effects of keto, including hunger, fatigue, low mood, irritability, constipation, headaches and “brain fog”. It also notes that many studies have been short, often 12 weeks or less, and that long-term safety remains an open question. It recommends consulting a physician and dietitian before starting.
Frequently asked questions
Is keto better than low-carb for weight loss?
Harvard’s review reports that, after one year, the results of a ketogenic diet were not significantly different from those of conventional weight-loss diets. The best approach is often the one you can sustain and that suits your health, which is a conversation for your doctor or dietitian.
Can I move between low-carb and keto?
Many people use the terms loosely, but they are different targets. If you are following a plan for a medical reason, stick to the one your healthcare team has agreed with you.
Where did the ketogenic diet come from?
According to Harvard’s review, it was introduced in 1920 as a treatment for epilepsy in children whose condition did not respond to medication. It became popular as a weight-loss diet much later.
Choosing your approach before you book
Decide which of the two you are actually following before you look at a menu, because it changes the questions you need to ask. For low-carb, one swap usually does it. For keto, check sauces, sides and drinks as well. Either way, more practical guides are in our Low-Carb and Health section, and any significant change to your diet is worth discussing with a health professional first.
