Question explored with the scientific record
How strong is the research supporting keto diet for reducing blood sugar and insulin resistance
The short version: the evidence shows a ketogenic diet can lower blood sugar and insulin resistance in the short term, but the studies are small, short, and often lack a proper control group.
The strongest evidence comes from a 2024 Iraqi study of adults with type 2 diabetes. After 90 days on a very-low-carbohydrate ketogenic diet, HbA1c dropped from 8.9% to 5.6% [1]. That is a large change. But the study had no control group. You cannot know how much of that drop came from the diet versus just being in a study, getting attention, or losing weight. A 2025 Yemeni study in hypertensive adults found fasting blood sugar fell from 129 to 103 mg/dL over two months, but HbA1c barely budged (5.69% to 5.59%, p=0.138) [4]. That matters because HbA1c reflects average blood sugar over months, not a single snapshot.
A 2015 critical review of nine meta-analyses found that when you only look at the higher-quality trials, low-carbohydrate diets do not outperform high-carbohydrate diets for glycemic control or weight loss [3]. The reason is simple: people struggle to stick to very low carbohydrate intake, and by the end of most studies the two groups are eating similar amounts of carbs. The short-term benefits seen in the uncontrolled studies may not last.
| Outcome | Before diet | After diet | Study type | Source |
|---|---|---|---|---|
| HbA1c (type 2 diabetes) | 8.9% | 5.6% | Pre-post, no control | [1] |
| Fasting blood sugar (hypertension) | 129 mg/dL | 103 mg/dL | Pre-post, no control | [4] |
| HbA1c (type 2 diabetes, 48 weeks) | 7.6% | 6.9% | Controlled trial | [14] |
The 2026 carnivore diet case report is a single person [2]. It shows what is possible, not what is probable. The PCOS scoping review [7] and the 2024 narrative review [11] both say the same thing: short-term improvements are real, but long-term data is missing.
My call: a ketogenic diet can lower blood sugar and insulin resistance in the short term, especially in people who stick with it, but the evidence does not show it is better than other diets over a year or more. Confidence: moderate for short-term effects, low for long-term superiority.
Sources used 19
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The effect of the keto diet on lipid profile with type two diabetic patients
This study evaluates the short-term metabolic effects of a very-low-carbohydrate ketogenic diet on glycemic control (HbA1c) and lipid profile in adults with type 2 diabetes in Kirkuk and Mosul, Iraq, finding a marked HbA1c reduction after 90 days and favorable changes in triglyc…
DOI: 10.33380/2305-2066-2024-13-4-1820 -
Reversing 20 years of diabetes using the carnivore diet in India: a case report
A 58-year-old Indian man with two decades of type 2 diabetes and hypertension achieved remission of both conditions within months after adopting a high-fat, very low-carbohydrate carnivore diet, with notable improvements in glycemic control and kidney function, though cancer pro…
DOI: 10.7762/cnr.2025.0026 -
A critical review of low‐carbohydrate diets in people with Type 2 diabetes
A critical review of meta-analyses on low-carbohydrate diets (LCD) in adults with type 2 diabetes, finding that when higher-quality studies are emphasized, LCDs do not outperform high-carbohydrate diets in glycemic control or body weight, with adherence issues and convergence of…
DOI: 10.1111/dme.12964 -
Association of ketogenic diet with glycemic control and hematological and biochemical parameters in Yemeni patients with primary hypertension.
A two-month, repeated-measures study in Yemeni adults with primary hypertension showing that a ketogenic diet improves glycemic control and hematological/biochemical parameters, with favorable lipid changes and no adverse effects on liver or kidney function, suggesting potential…
DOI: 10.59628/jchm.v19i6.2330 -
Investigating the Effect of Two Types of Aerobic and Resistance Training during a Ketogenic Diet on the Serum Levels of Adipokines and Insulin Resistance in Overweight or Obese Men
This randomized controlled trial assessed the effects of combining a ketogenic diet with two types of exercise (aerobic or resistance training) on adipokine levels and insulin resistance in overweight/obese men, finding improvements in adipokines with both training types and som…
DOI: 10.32592/nkums.15.1.60 -
Cardiometabolic disorders affect myocardial [18F]fluorodeoxyglucose uptake– impact on diagnostic PET/CT imaging
In 100 adults undergoing cardiac 18F-FDG PET/CT after a short-term ketogenic diet, the study shows that cardiometabolic disorders are linked to reduced myocardial FDG uptake with sex-specific determinants of suppression, and that pre-imaging beta-hydroxybutyrate (BHB) and free f…
DOI: 10.1186/s13550-025-01278-8 -
Polycystic Ovary Syndrome and the Effects of a Ketogenic Diet: A Scoping Review
This scoping review synthesizes eight studies (2019–2025) on overweight/obese women with polycystic ovary syndrome (PCOS) to evaluate the effects of ketogenic diets (VLCKD, CKD, and KEMEPHY) on weight, metabolic/hormonal parameters, and reproductive outcomes, finding favorable s…
DOI: 10.3390/nu17172893 -
Ketogenic diet rescues cognition in ApoE4+ patient with mild Alzheimer's disease: A case study
A 71-year-old ApoE4 heterozygous female with mild Alzheimer's disease and metabolic syndrome underwent a 10-week ketogenic diet with time-restricted eating, cognitive training, and exercise, leading to significant improvements in metabolic biomarkers and MoCA cognition, suggesti…
DOI: 10.1016/j.dsx.2019.01.035 -
Therapeutic effectiveness of low-calorie ketogenic diet on body composition and biochemical parameters in polycystic ovary syndrome: an ıntervention study
A small, four-week, single-arm trial in overweight/obese women with PCOS shows that a very-low-carbohydrate, low-calorie ketogenic diet reduces body weight and central adiposity and improves several metabolic/hormonal biomarkers, suggesting potential short-term therapeutic value…
DOI: 10.20960/nh.05901 -
Ketogenic diet delays the phase of circadian rhythms and does not affect AMP-activated protein kinase (AMPK) in mouse liver
The study investigates how a ketogenic diet alters circadian clock regulation and metabolic signaling in mice, revealing brain-delayed circadian rhythms with increased brain pAMPK and SIRT1 and reduced brain mTOR signaling, combined with reduced hepatic mTOR signaling, increased…
DOI: 10.1016/j.mce.2015.09.012 -
Ketogenic diet and metabolic health: A review of its impact on type 2 diabetes and obesity. Analysis of research on the ketogenic diet in the context of treating metabolic disorders
A comprehensive narrative review synthesizing current evidence on the ketogenic diet's impact on obesity and type 2 diabetes, detailing potential metabolic benefits, mechanisms, risks, and comparisons with other dietary approaches, while highlighting the need for more long-term …
DOI: 10.12775/jehs.2024.71.55923 -
Ketogenic diet ameliorates MASLD via balancing mitochondrial dynamics and improving mitochondrial dysfunction
This study demonstrates that a 2-week ketogenic diet partially ameliorates MASLD in a high-fat-diet mouse model by restoring hepatic mitochondrial dynamics (reducing Fis1/Drp1) and improving mitochondrial function, while in HepG2 cells the ketone body β-hydroxybutyrate counters …
DOI: 10.1038/s41387-025-00391-w -
The glycaemic benefits of a very‐low‐carbohydrate ketogenic diet in adults with Type 1 diabetes mellitus may be opposed by increased hypoglycaemia risk and dyslipidaemia
This observational study investigates the effects of a very-low-carbohydrate ketogenic diet on glycaemic control in adults with Type 1 diabetes, revealing excellent HbA1c levels but increased risks of hypoglycaemia and dyslipidaemia.
DOI: 10.1111/dme.13663 -
Comparing the Intervention Effects of the Low-carbohydrate Diet and the Ketogenic Diet on Type 2 Diabetes
This study compares the effects of low-carbohydrate and ketogenic diets on type 2 diabetes, highlighting their short-term benefits and potential side effects, ultimately suggesting that neither diet is a long-term solution for managing the condition.
DOI: 10.54097/hset.v66i.11623 -
Effects of Ketogenic Diet on Glucolipid Metabolism
This study investigates the effects of a ketogenic diet on glucolipid metabolism, revealing significant improvements in BMI, waist circumference, and insulin secretion in individuals with Type 2 diabetes, while also highlighting the need for further research due to limitations i…
DOI: 10.54097/hset.v66i.11615 -
An unfortunate challenge: Ketogenic diet for the treatment of Lennox–Gastaut syndrome in tyrosinemia type 1
This study reports the use of a ketogenic diet as a treatment for a child with Lennox-Gastaut syndrome and tyrosinemia type 1, highlighting its potential effectiveness despite additional dietary restrictions.
DOI: 10.1016/j.ejpn.2016.02.015 -
Medical management of children with type 1 diabetes on low‐carbohydrate or ketogenic diets
The authors developed and implemented a one-page clinical protocol and accompanying educational materials to safely monitor pediatric and adolescent type 1 diabetes patients following a low-carbohydrate or ketogenic diet, detailing growth, glycemic control, bone and cardiometabo…
DOI: 10.1111/pedi.13179 -
When and what to eat? A scoping review of health outcomes of fasting in conjunction with a low-carbohydrate diet
This scoping review maps the health outcomes of combining a low-carbohydrate diet (LCD) with fasting, synthesizing evidence from 15 studies across children and adults to assess potential benefits and limitations of the approach, including epilepsy in children and improvements in…
DOI: 10.1017/s0007114522001854 -
The Many Faces of Glut1 Deficiency Syndrome
This study investigates glucose transporter protein type 1 deficiency syndrome, detailing a cohort of patients with varying clinical presentations, the identification of SLC2A1 mutations, and the effectiveness of dietary interventions such as the ketogenic diet.
DOI: 10.1177/0883073812471718