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Does the keto diet help you live longer?

What you hear: “A ketogenic diet is the single healthiest way to eat and will help you live longer.”

What the studies found

A pooled analysis of 13 trials lasting at least a year found people on a very low-carb ketogenic diet lost about 0.9 kg more than those on a low-fat diet, with lower triglycerides and higher HDL but also higher LDL ('bad') cholesterol. In a 12-week crossover trial in 33 people with prediabetes or type 2 diabetes, keto and a Mediterranean-style diet gave similar blood sugar control, but LDL rose about 10% on keto versus a 5% fall on the Mediterranean diet, and keto was harder to stick with. No trial has tested whether keto helps people live longer. In observational data covering 432,179 people, eating under 40% of calories from carbs went with a 20% higher death rate than moderate intake, and low-carb eating based on animal foods looked worse than plant-based versions; this is a link, not proof of cause.

Take care: Keto can raise LDL cholesterol substantially in some people; people taking diabetes or blood pressure medicines, or who are pregnant, should only try it with medical supervision.

What you could do

If low-carb suits you, build it on vegetables, nuts, olive oil and fish, and have your cholesterol checked after a few months.

See it in the habit library, with what it means for your own longevity score.

Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.

How we judged it

Not proven: Not enough good human evidence yet, either way. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.

The studies, in their own words

1. Bueno et al. Br J Nutr 2013

   Individuals assigned to a VLCKD showed decreased body weight (weighted mean difference -0·91 (95% CI -1·65, -0·17) kg, 1415 patients)

2. Bueno et al. Br J Nutr 2013

   increased HDL-C(weighted mean difference 0·09 (95% CI 0·06, 0·12) mmol/l, 1257 patients) and LDL-C (weighted mean difference 0·12 (95% CI 0·04,0·2) mmol/l, 1255 patients)

3. Gardner et al. Am J Clin Nutr 2022 (Keto-Med)

   LDL cholesterol was higher for the WFKD [percentage changes, +10% (SEM, 4%) compared with -5% (SEM, 5%) for the Med-Plus; P = 0.01]

4. Seidelmann et al. Lancet Public Health 2018

   In the meta-analysis of all cohorts (432 179 participants), both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake, which was consistent with a U-shaped association (pooled hazard ratio 1·20, 95% CI 1·09-1·32 for low carbohydrate consumption

5. Seidelmann et al. Lancet Public Health 2018

   mortality increased when carbohydrates were exchanged for animal-derived fat or protein (1·18, 1·08-1·29) and mortality decreased when the substitutions were plant-based (0·82, 0·78-0·87).

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