Quick answer: Glucagon is a pancreatic hormone that works opposite to insulin. When blood sugar is low, during fasting, exercise or a low-carb diet, glucagon signals the liver to break down glycogen into glucose and promotes fat breakdown and ketone production. On keto, the balance between lower insulin and higher glucagon helps sustain ketosis.
Key takeaways
Glucagon is released when blood sugar falls, prompting the liver to release stored glucose and make new glucose.
When carbohydrates are limited, glucagon may help release fatty acids from fat tissue and encourage ketone production.
Insulin and glucagon work like a seesaw, and lower insulin with relatively higher glucagon favors fat burning.
What glucagon does
Alpha cells in the pancreas release glucagon when blood sugar falls. It prompts the liver to release glucose from glycogen (glycogenolysis) and make new glucose (gluconeogenesis).
Glucagon and ketosis
When carbs are limited, glucagon may help release fatty acids from fat tissue and encourage the liver to turn them into ketones. See what is ketosis.
Insulin and glucagon balance
These two hormones work as a seesaw. Lower insulin and relatively higher glucagon favor fat burning. See the role of insulin.
Healthy aging lens
Healthy hormone signaling between meals supports metabolic flexibility, the ability to switch fuels easily.
What the research shows
Glucagon itself is rarely measured in diet trials, but studies of ketogenic diets show the hormonal shifts that accompany it, especially lower insulin.
Six weeks of keto in healthy adults (Urbain 2017, before-and-after study). 42 healthy adults followed a ketogenic diet (about 72% fat, 21% protein and 8% carbohydrate) without calorie limits for 6 weeks. They lost about 2 kg, split equally between fat and lean mass. Peak power dropped 4%, LDL cholesterol rose about 11%, and insulin fell 22%. A limitation is that there was no control group, so changes can’t be fully separated from other factors.
Keto under tightly controlled conditions (Hall 2016, metabolic ward study). 17 men with overweight or obesity lived on a research ward, eating a high-carbohydrate diet for 4 weeks and then a ketogenic diet with the same calories and protein for 4 weeks. Energy use rose a little on keto (about 57 to 151 kcal a day depending on the method), but body fat loss actually slowed, while loss of lean mass increased. A limitation is that there were only 17 men, the diets were not randomized in order, and 4 weeks may be too short to see longer-term adaptation.
Strength of the evidence: Evidence about glucagon on keto comes mostly from physiology research rather than diet trials, so this area is less well studied.
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.
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Questions to bring to your clinician
These questions can help you get the most out of your next visit.
How do my blood sugar patterns between meals look, and would keto change them for the better?
How does my body keep energy steady between meals on keto?
Could I feel shaky between meals at first, and what should I do if I do?
Is there anything in my health that makes longer gaps between meals unwise?
Frequently asked questions
What does glucagon do?
It raises blood sugar by releasing stored glucose and supports fat burning.
How is glucagon different from insulin?
Insulin lowers blood sugar; glucagon raises it.
Does glucagon help ketosis?
Yes, it supports fat breakdown and ketone production.
When is glucagon released?
When blood sugar is low, such as during fasting or exercise.
Sources
- Gromada J, Franklin I, Wollheim CB. Alpha-cells of the endocrine pancreas: 35 years of research but the enigma remains. Endocr Rev 2007. PMID: 17261637. https://pubmed.ncbi.nlm.nih.gov/17261637/
- Jiang G, Zhang BB. Glucagon and regulation of glucose metabolism. Am J Physiol Endocrinol Metab 2003. PMID: 12626323. https://pubmed.ncbi.nlm.nih.gov/12626323/
- Goodpaster BH, Sparks LM. Metabolic Flexibility in Health and Disease. Cell Metab 2017. PMID: 28467922. https://pmc.ncbi.nlm.nih.gov/articles/PMC5513193/
- NIDDK: Insulin Resistance & Prediabetes
- MedlinePlus: Carbohydrates
- Urbain P, et al. Impact of a 6-week non-energy-restricted ketogenic diet on physical fitness, body composition and biochemical parameters in healthy adults. Nutr Metab (Lond) 2017. PMID: 28239404. https://pubmed.ncbi.nlm.nih.gov/28239404/
- Hall KD, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr 2016. PMID: 27385608. https://pubmed.ncbi.nlm.nih.gov/27385608/
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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