Few topics divide a dinner table like keto. Much of the best research on it comes from Dr. Jeff Volek and Dr. Stephen Phinney, who have spent their careers studying what happens when the body shifts to burning fat. Their work shows carbohydrate restriction is a powerful tool, with trade-offs worth managing.
Blood sugar: the strongest case
In a two-year trial co-led by Volek and Phinney, 262 adults with type 2 diabetes followed a ketogenic diet with remote coaching and medical support. HbA1c fell 12%, body weight fell 10%, insulin use dropped 62%, and sulfonylurea use stopped entirely. More than half met the study’s definition of diabetes reversal, while a usual-care group saw no meaningful change. The trial wasn’t randomized, so it can’t prove cause on its own.
The randomized evidence points the same way, with a warning. A 2021 BMJ meta-analysis found low-carb diets helped about 32 more people out of every 100 reach an HbA1c below 6.5% at six months, but the advantage faded by 12 months. Support and accountability appear to be what make results last.
Fuel for performance
In Volek and Phinney’s FASTER study, keto-adapted ultra-endurance athletes burned fat at 1.54 grams per minute, about 2.3 times the rate of high-carb athletes. During a three-hour run, both groups used and restored muscle glycogen similarly. Fat adaptation changes how you fuel, though the study didn’t measure whether it makes you faster.
Heart markers: look deeper than LDL
After one year in the diabetes trial, LDL cholesterol rose about 10%. Total LDL particle number and ApoB didn’t change, small LDL particles fell 21%, the triglyceride-to-HDL ratio fell 29%, and the 10-year cardiovascular risk score dropped 12%.
Responses vary. In Stanford’s Keto-Med trial, LDL rose 10% on keto but fell 5% on a Mediterranean diet, and keto cut fibre, folate, vitamin C and magnesium.
Medication matters too. Diabetes Canada cautions that people on insulin or sulfonylureas may need dose changes to avoid low blood sugar, and that SGLT2 inhibitors raise the risk of ketoacidosis on low-carb diets.
How to apply it
- Start with your goal. Blood sugar control has the strongest evidence; endurance athletes can use fat adaptation strategically.
- Build on whole foods. Non-starchy vegetables, eggs, fish, meat, olive oil, nuts and seeds protect your fibre and micronutrients.
- Test, don’t guess. Check HbA1c and a full lipid panel, including ApoB, before you start and about three months in.
- Get support. The best long-term results came with coaching, not willpower alone.
- Loop in your physician if you take medication for blood sugar or blood pressure.
Carbohydrate restriction isn’t magic, and it isn’t dangerous by default. Done well and monitored, it’s one of the most effective tools we have.
Want help building a nutrition plan that fits your goals and your training? The Longevity Path coaching team can help you make it stick.
References
- Athinarayanan SJ, Adams RN, Hallberg SJ, McKenzie AL, Bhanpuri NH, Campbell WW, Volek JS, Phinney SD, McCarter JP. Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: a 2-year non-randomized clinical trial. Frontiers in Endocrinology. 2019;10:348. https://www.google.com/url?q=https://doi.org/10.3389/fendo.2019.00348&source=gmail&ust=1793662968793000&sa=E
- Bhanpuri NH, Hallberg SJ, Williams PT, et al. Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study. Cardiovascular Diabetology. 2018;17(1). https://www.google.com/url?q=https://doi.org/10.1186/s12933-018-0698-8&source=gmail&ust=1793662968793000&sa=E
- Volek JS, Freidenreich DJ, Saenz C, et al. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism. 2016;65(3):100-110. https://www.google.com/url?q=https://core.ac.uk/download/214452177.pdf&source=gmail&ust=1793662968793000&sa=E
- Goldenberg JZ, Day A, Brinkworth GD, et al. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis of published and unpublished randomized trial data. BMJ. 2021;372:m4743. https://www.google.com/url?q=https://doi.org/10.1136/bmj.m4743&source=gmail&ust=1793662968793000&sa=E
- Gardner CD, Landry MJ, Perelman D, et al. Effect of a ketogenic diet versus Mediterranean diet on glycated hemoglobin in individuals with prediabetes and type 2 diabetes mellitus: the interventional Keto-Med randomized crossover trial. American Journal of Clinical Nutrition. 2022. https://www.google.com/url?q=https://doi.org/10.1093/ajcn/nqac154&source=gmail&ust=1793662968793000&sa=E
- Diabetes Canada. Low carbohydrate diets for adults with diabetes: summary. https://www.google.com/url?q=https://www.diabetes.ca/advocacy—policies/our-policy-positions/low-carbohydrate-diets-for-adults-with-diabetes–summary&source=gmail&ust=1793662968793000&sa=E
