Nutritional ketosis is well-tolerated, even in type 1 diabetes: the ZeroFive100 Project; a proof-of-concept study
Authors: Lake Ian 
Published: August 2021

Purpose of review
The objective of this study was to test the feasibility of exercising over a 5-day period while fasting, in those with and without type 1 diabetes mellitus (T1DM).
Eight individuals, ages 29--62 years, two with T1DM, walked/ran around 20 miles per day for five consecutive days while only consuming water. All eight individuals completed the project with no physical injuries or problems with diabetes control. The blood glucose levels ranged from less than 3 mmol/l to 7 mmol/l in those without T1D, and less than 3 mmol/l to 9 mmol/l in those with T1D. The continuous glucose traces in those with T1D showed little variability in glucose levels. The participants without T1D had no symptoms from blood glucose under 3 mmol/l. Ketone levels ranged from 0.3 to 7.5 and the ketones for those with T1D were no different to ketones in those without T1D. The respiratory quotient was overwhelmingly in the fat-burning range. There was very little subjective hunger, nor did it negatively affect mood. In keto-adapted individuals, with or without T1DM, prolonged exercise for 5 days while in nutritional ketosis was feasible, and well tolerated.

Recent findings
Eight adults, ages 28–62 years, trained for and completed a 5-day zero calorie fast covering 100 miles over 5 days. Training involved each individual preparing for the event according to their own programme. Typically, it involved both cardiovascular and strength training with the addition of practice water only fasts over 24–72 h or more based upon the individual's assessment of what was needed to complete the event. There was no formal protocol provided for this. The recommendation was that the participants would be keto adapted and trained to a level sufficient to complete the 5-day event. Keto adaptation was measured by ketone blood testing of betahydroxybutyrate. Two people had type 1 diabetes. All but one person was keto-adapted ahead of the event. All eight individuals completed the project with no physical injuries or problems with diabetes control. Prolonged fasting did neither lead to hunger nor did it negatively affect mood, which, if anything, was enhanced in most individuals. All keto-adapted people were shown to be burning fat stores throughout the 5 days, and everyone was measured to be in a state of nutritional ketosis. In type 1 diabetes, and ketones were in the same range as those without diabetes, insulin volumes were considerably reduced, and glucose control was close to physiological: nutritional ketosis is not a risk factor for diabetic ketoacidosis; consumption of sugar for energy is not required for distances of up to 100 miles in keto-adapted people; people who inject insulin do not necessarily need to consume carbohydrates unless rescuing a hypoglycaemic attack.

Summary
The findings from this project should provide reassurance to those clinicians who want to provide the option of a ketogenic lifestyle to their patients with type 1 diabetes. They also confirm that the fat stores are available for aerobic respiration without apparent negative consequences on physical or mental function.

Video abstract

http://links.lww.com/COE/A24