Ketogenic (Keto) Diet
A very-low-carb, high-fat approach that shifts your metabolism toward ketosis.
Keto lives and dies by hitting precise carb and fat targets — our Macro Calculator can turn a calorie target into keto-appropriate gram targets.
How It Works
Keto is a very-low-carbohydrate, high-fat diet — roughly 70–80% of calories from fat, 10–20% from protein, and only 5–10% from carbohydrate, typically 20–50g of net carbs per day. Restrict carbs that much and the body shifts from burning glucose to burning fat and producing ketones as an alternative fuel source — the metabolic state ("ketosis") the diet is named for. It was originally developed in the 1920s as a physician-supervised treatment for drug-resistant epilepsy, and remains in clinical use for that today, precisely dosed and monitored — a distinct use case from the popular weight-loss version of the diet.
The Research
Keto shows short-term benefits similar to other calorie-restricted diets but no clear long-term advantage over them — and it comes with real adherence and safety caveats worth knowing before you start.
Meta-analysis: López-Espinoza MÁ, et al. "Effect of a Ketogenic Diet on the Nutritional Parameters of Obese Patients: A Systematic Review and Meta-Analysis," Nutrients, 2021. Pooling 10 RCTs, keto showed no significant advantage over balanced, calorie-restricted diets on BMI or cholesterol markers, and the authors advise against continuing it beyond 12 weeks, flagging side effects like headache, muscle weakness, constipation, and hair loss.Read the systematic review →
Additional research:
Yancy WS Jr, Olsen MK, Guyton JR, Bakst RP, Westman EC. "A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia: A Randomized, Controlled Trial," Annals of Internal Medicine, 2004. A 24-week RCT (n=120) found better participant retention and greater weight loss on keto than on a low-fat diet, with larger triglyceride drops and HDL gains during the active weight-loss period.
Read the trial →
Parry-Strong A, et al. "Very low carbohydrate (ketogenic) diets in type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials," Diabetes, Obesity and Metabolism, 2022. Across 8 RCTs, keto showed no clear advantage over other diets on weight or HbA1c after 12 months, though it modestly lowered triglycerides and raised HDL — worth flagging that dropout in the keto arms reached as high as 54% in some of the pooled trials.
Read the meta-analysis →
Safety signal: Norwitz NG, Soto-Mota A, Feldman D, Parpos S, Budoff M. "Case Report: Hypercholesterolemia 'Lean Mass Hyper-Responder' Phenotype Presents in the Context of a Low Saturated Fat Carbohydrate-Restricted Diet," Frontiers in Endocrinology, 2022. Documents that lean, metabolically healthy people can see dramatic LDL cholesterol increases on very-low-carb diets — a real effect some people should be aware of and get their lipids checked for, even though its long-term cardiovascular consequences are still being studied.
Read the case report →
Food Examples
Emphasized: olive and avocado oil, butter, fatty fish (salmon, sardines), eggs,
cheese, nuts and seeds, avocado, poultry and beef, and low-carb vegetables (leafy greens, broccoli,
cauliflower, zucchini, peppers).
Excluded or limited: bread, rice, pasta, cereal, sugar and sweets, most fruit
(small amounts of berries sometimes tolerated), potatoes, corn, legumes (beans, lentils), and most
milk (moderate cream or hard cheese only).
A Sample Day
Breakfast: eggs scrambled in butter with spinach and cheese.
Lunch: grilled chicken salad with olive oil, avocado, and leafy greens.
Dinner: salmon with roasted broccoli in olive oil and a side of cauliflower rice.
Snacks: almonds, or celery with cream cheese.
Who It Might Suit
Not recommended without medical guidance for anyone with pancreatitis, liver or gallbladder disease, certain kidney conditions, pregnancy, or for anyone on insulin or SGLT2 inhibitors (risk of euglycemic ketoacidosis) or other glucose-lowering medications. Beyond that, its restrictiveness makes long-term adherence genuinely difficult — trial dropout reached over half of participants in some of the research above — so it tends to suit people who do well with firm food-category rules and don't mind cutting out entire food groups, more than people who want a flexible, indefinitely sustainable pattern.