Quick answer: Keto works by limiting carbohydrates so much that glucose and insulin fall. The body uses up stored glucose (glycogen), then breaks down fat. The liver converts fatty acids into ketone bodies, mainly beta-hydroxybutyrate, which fuel the brain and muscles. Consistently making and using ketones is called ketosis.
Key takeaways
When net carbohydrates are kept very low, insulin falls and glycogen stores are used up, so the body turns to fat and ketones for fuel.
Keto relies on a high-fat, moderate-protein and very low-carbohydrate balance.
Nutritional ketosis is a normal, controlled state, while diabetic ketoacidosis is a dangerous condition seen mainly in type 1 diabetes.
From glucose to ketones
Carbohydrates are usually your cells’ preferred fuel. When net carbs are kept very low, insulin falls and glycogen stores are used up, forcing the body to adapt.
Key concepts
Macronutrient ratio
High fat, moderate protein, very low carbohydrate. Calculate yours with the keto macro calculator.
Depleting glucose reserves
With little incoming carbohydrate, the body draws on glycogen in the liver and muscles, which takes a few days.
Lower insulin
Insulin promotes fat storage. Lower insulin lets fat be released for fuel. See the role of insulin.
Ketone production
The liver turns fatty acids into acetoacetate, beta-hydroxybutyrate and acetone, alternative fuels for the brain and other organs.
Ketosis
When the body consistently produces and uses ketones, it is in nutritional ketosis. See what is ketosis.
Nutritional ketosis vs. ketoacidosis
Nutritional ketosis is a normal, controlled state. Diabetic ketoacidosis is a dangerous condition, mainly in type 1 diabetes, where ketones and blood sugar rise very high. People with diabetes need medical supervision.
Healthy aging lens
Ketones are not just fuel; they also act as signaling molecules that may lower oxidative stress and inflammation, though much of this research is early.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have diabetes or take insulin, sulfonylureas or SGLT2 inhibitors (risk of low blood sugar or ketoacidosis), or if you take blood pressure medication or diuretics. The same is true if you have kidney, liver, gallbladder or pancreas disease, or high cholesterol, if you are pregnant, breastfeeding, or have a history of disordered eating, or if you want a keto plan tailored to your labs and goals.
See a medical provider promptly for nausea and vomiting, abdominal pain, confusion, fruity-smelling breath with rapid breathing, or very high blood sugar or ketone readings, which can signal ketoacidosis.
Want a keto plan that’s safe for your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Given my blood sugar and medications, would ketosis be safe for me?
Could any of my current medications or supplements interact with the options discussed here?
Would any lab testing add useful information in my situation, or is it reasonable to start with daily habits?
Which one or two changes would be most worthwhile for me to focus on first?
Frequently asked questions
How long does it take to get into ketosis?
Often a few days of very low carb intake, but it varies.
What are ketones?
Molecules the liver makes from fat that serve as fuel.
Is ketosis the same as ketoacidosis?
No. Ketoacidosis is a medical emergency.
Why does insulin matter?
Lower insulin allows stored fat to be used for energy.
Sources
- Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. Diabetes Metab Res Rev 1999. PMID: 10634967. https://pubmed.ncbi.nlm.nih.gov/10634967/
- Dhatariya KK, et al. Diabetic ketoacidosis. Nat Rev Dis Primers 2020. PMID: 32409703. https://pubmed.ncbi.nlm.nih.gov/32409703/
- Newman JC, Verdin E. Ketone bodies as signaling metabolites. Trends Endocrinol Metab 2014. PMID: 24140022. https://pmc.ncbi.nlm.nih.gov/articles/PMC4176946/
- Shimazu T, et al. Suppression of oxidative stress by β-hydroxybutyrate, an endogenous histone deacetylase inhibitor. Science 2013. PMID: 23223453. https://pmc.ncbi.nlm.nih.gov/articles/PMC3735349/
- Puchalska P, Crawford PA. Multi-dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics. Cell Metab 2017. PMID: 28178565. https://pmc.ncbi.nlm.nih.gov/articles/PMC5313038/
- MedlinePlus: Carbohydrates
- MedlinePlus: Diabetic Ketoacidosis
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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