DIETS
The keto diet
A very low-carb, high-fat diet that puts your body into ketosis
- Eat plenty of
- Meat, fish, eggs, cheese, butter, oils, avocado, nuts
- Eat some
- Leafy and non-starchy vegetables, a few berries
- Avoid
- Bread, pasta, rice, potatoes, sugar, most fruit, beans
- Carbs
- About 20 to 50 g a day
What it is
The ketogenic diet was first used in medicine, a century ago, to treat epilepsy. With so few carbohydrates, the liver turns fat into ketones, which the brain and muscles use for fuel. This state, ketosis, usually starts within two to four days. Typical proportions are about 70 to 80% of calories from fat, 15 to 20% from protein and 5 to 10% from carbohydrate.
What to eat
| Food group | How often | Examples |
|---|---|---|
| Meat, fish and eggs | Every meal | Chicken, beef, salmon, sardines, eggs |
| Low-carb vegetables | Every meal | Spinach, lettuce, zucchini, cauliflower, broccoli |
| Fats and oils | Every meal | Olive oil, butter, avocado |
| Full-fat dairy | Daily | Cheese, cream, plain Greek yogurt |
| Nuts and seeds | Daily, a handful | Macadamias, pecans, walnuts, chia |
| Berries | Occasionally | A few raspberries or strawberries |
| Bread, pasta, rice, potatoes | Not at all | Replaced by vegetables |
| Sugar and most fruit | Not at all | Sweets, juice, bananas, grapes |
A sample day
Keto, one day
- BreakfastOmelet with cheese and spinach, cooked in butter
- LunchTuna salad with olive oil, avocado and olives
- SnackA handful of macadamia nuts
- DinnerRoast chicken thighs with green beans and garlic butter
What the research found
Key study
Slightly more weight lost after a year
- Meta-analysis
- 13 trials, 1,415 adults
- 12 months or more
Adults on a very low-carb ketogenic diet lost about 0.9 kg more than those on a low-fat diet. Their triglycerides fell and their HDL (“good”) cholesterol rose more, but their LDL cholesterol also rose more.
Key study
No metabolic advantage for fat loss
- Metabolic ward study
- 17 men
- 8 weeks
Men lived in a research ward and ate the same calories on a high-carb diet and then on a keto diet. On keto they used only slightly more energy, about 57 calories a day, and their body fat loss slowed rather than sped up.
In another ward study, people ate as much as they wanted of a plant-based low-fat diet and of an animal-based keto diet, two weeks each: they ate about 690 fewer calories a day on the low-fat diet, and only that diet led to significant body fat loss 3. In people with prediabetes or type 2 diabetes, keto and a Mediterranean diet lowered blood sugar similarly over 12 weeks, but LDL cholesterol rose on keto, and people found the Mediterranean diet easier to keep up afterwards 4.
Good for
- People who like meat, fish, eggs and dairy
- Feeling full on fewer meals
- Lowering triglycerides and blood sugar, with medical advice
Watch out for
- The keto flu in the first week
- Very little fiber, fruit or whole grains
- Higher LDL cholesterol in some people
- Hard to keep up socially
The keto flu
In the first days, many people feel tired, foggy, irritable or dizzy, with headaches and cramps. It’s mostly the body adapting and losing water and salt as glycogen runs out. Drinking plenty of water and adding a little salt to food usually helps, and it passes within a week or two.
How to start
Five first steps
- Plan a week of meals before you start, so you aren’t left with nothing to eat.
- Cut bread, pasta, rice, potatoes, sugar and juice.
- Fill half your plate with low-carb vegetables for fiber.
- Prefer olive oil, nuts, fish and avocado to processed meats and lots of butter.
- Have your cholesterol checked after a few months.
Common mistakes
- Eating unlimited fat because “fat doesn’t count”: calories still count.
- Leaving out vegetables, then wondering about constipation.
- Relying on processed meats and keto snack products.
- Staying on strict keto for years without checking your blood lipids.
With an eating window
Questions
How many carbs can you eat on keto?
Usually 20 to 50 g of carbohydrate a day. Most people stay in ketosis below about 50 g, but it varies.
Does keto burn more fat?
Not by itself. In metabolic ward studies, keto didn’t speed up fat loss when calories were the same 2. People often lose weight on keto because they eat less.
Is keto safe in the long term?
Long-term evidence is limited. LDL cholesterol rises in some people, and fiber intake is low, so many doctors suggest keto for a limited time with regular blood tests.
Sources
- Bueno NB, de Melo ISV, de Oliveira SL, et al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr. 2013;110(7):1178-1187. doi.org/10.1017/S0007114513000548
- Hall KD, Chen KY, Guo J, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr. 2016;104(2):324-333. doi.org/10.3945/ajcn.116.133561
- Hall KD, Guo J, Courville AB, et al. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med. 2021;27(2):344-353. doi.org/10.1038/s41591-020-01209-1
- Gardner CD, Landry MJ, Perelman D, et al. Effect of a ketogenic diet versus Mediterranean diet on glycated hemoglobin in individuals with prediabetes and type 2 diabetes mellitus: The interventional Keto-Med randomized crossover trial. Am J Clin Nutr. 2022;116(3):640-652. doi.org/10.1093/ajcn/nqac154
MAKE IT A HABIT
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dieting.app is general information, not medical advice. If you are pregnant or breastfeeding, have diabetes, kidney disease or a history of eating disorders, or take medication, talk to your doctor before changing how you eat.