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Zero Five 100

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Eight people covered a distance of 100 miles, over five days, with zero calories, to gather information to re-think diabetes management.

This was a thoroughly researched and planned activity to primarily explore the safety and physiological effects of ketosis in people with or without diabetes. We hope you find that this unique science project stimulates your interest. It is not a recommendation to do similar.

Read the Medical Paper

Nutritional ketosis is well-tolerated, even in Type 1 Diabetes; a proof-of-concept study:


The Task

A group of 8 runners, two with Type 1 Diabetes (T1D), and including Olympic athlete James Cracknell, have covered 100 miles over five days, between Henley and Bristol, consuming zero calories. The Zero Five 100 challenge was set up by Dr Ian Lake, who has Type 1 Diabetes (T1D), aiming to explore the safety and effectiveness of fueling from stored body fat during a five days fasting and endurance exercise.

The Team

  • Dr Ian Lake, GP with Type 1 Diabetes.
  • Jon Furniss, Engineer with Type 1 Diabetes.
  • James Cracknell, Olympic Athlete and Journalist.
  • Dr Trudi Deakin, Dietitian.
  • Dr Ali Ibrahim, Consultant Psychiatrist.
  • Gayle Gerry, NHS Practice Nurse.
  • Steve Bennett, Businessman (Primal Living).
  • Jake Thompson, Businessman on a ketogenic diet weight programme.

All individuals were physically and mentally fit, and well nourished. They had trained in both fasting techniques, and in covering the distanced needed per day. Individuals were free to cease participation at any time. All volunteers completed the project safely and well, in high spirits.

Disclaimer: The team are not advocating anyone to undertake such a project themselves. Neither are they advocating that this is an optimal or desirable form of activity. It was an experiment in metabolic performance. This was not a test to assess the limits of human performance. Nor was it an experiment in starvation. There are significant differences between fasting and starvation. Fasting is time delayed eating in well-nourished individuals, as opposed to starvation which results in nutritional deficiencies and malnutrition.

The Route

From Henley on Thames to Bristol following the River Thames and Kennet & Avon Canal.
The project took place from 19th to 23rd September 2020.


A ketogenic diet, characterized by consuming fewer than 50g of carbs per day over 2-4 weeks, triggers the body’s fat-burning mode, unlocking a substantial and underutilized energy reserve. Research has demonstrated that individuals with diabetes can effectively manage their condition and enhance metabolic health through adherence to a ketogenic diet, surpassing the effectiveness of current medical nutritional advice. Diabetes, affecting 8% of the UK population (approximately 5 million people) and costing £10 billion annually, presents a significant societal burden, with projections indicating a worsening situation for Type 2 Diabetes (T2D). Alarmingly, fewer than 10% of individuals with Type 1 Diabetes (T1D) meet NICE guideline targets through conventional management, while 90% achieve success with a ketogenic diet, as evidenced by studies such as that conducted by Lennerz-Ludwig (source). These findings underscore the availability of evidence-based alternatives to standard care, prompting a critical reassessment of our approach to managing the condition. This imperative is particularly relevant for the general population and crucial for pandemic preparedness, given the metabolic underpinnings of significant comorbidities for COVID-19, including obesity, high blood pressure, diabetes, and cardiovascular disease.

Furthermore, complications of diabetes are predominantly iatrogenic, stemming from the excessive use of medication and unnecessarily high carbohydrate recommendations. It is important to recognize that iatrogenic diabetic illness is potentially preventable and does not inevitably accompany life-saving medication management.

The design of this project aimed to present a substantial personal challenge to each participant while addressing concerns expressed by sports scientists and medical specialists regarding the safety and feasibility of ketogenic diets, especially in diabetes treatment. Deliberately adopting an ‘extreme’ approach, the project sought to explore the practical limits of a ketogenic lifestyle, with findings poised to offer insights applicable to both normal and diabetic ketogenic lifestyles.

Carbohydrate vs Fat Fueling

Advice via dietary guidelines to consume 55% of total energy from carbs makes it incredibly difficult for a person with diabetes to control their condition since they are essentially carbohydrate intolerant. Hence, current dietary advice is akin to pouring fuel on the fire of diabetes.

The body has the potential to store energy for future use.  Glucose is stored as glycogen and has a capacity to provide around 2000calories of energy. By contrast estimated fat stores in normal-weight individuals are vast.  And women have more body fat than men. For example, a 60kg women with a typical 25% body fat has 135,000 calories of fat stored in her body!! We aimed to explore the potential of that fat store and prove that starvation would not occur, also that there would be no significant muscle protein breakdown during the event.  The event distance approximates to a mere 20,000 calories of the fat store, so at the very low end of the range of the fat ‘tank’.  Breath metabolic testing showed our bodies were fat-burning throughout.

Complications of diabetes are mainly iatrogenic (use of high volumes of medication and higher than necessary carbohydrate recommendations).  Diabetic iatrogenic illness is potentially preventable & does not need to be thought of as an inevitable consequence of life-saving medication management.

This project was designed to be a significant personal challenge for each participant, but also to explore concerns expressed by sports scientists and medical specialists regarding the safety and practicality of ketogenic diets, especially in the treatment of diabetes.  It was deliberately ‘extreme  ’to explore the practical limits of ketogenic lifestyle.  Findings should then easily translate to normal and diabetic ketogenic lifestyles.

Measurements: Weight, CGM, ketones, body composition, etc.

Project Results

We investigated and demonstrated the following:

The two people with T1D found, as expected, that the common concern that fat burning leads to diabetic ketoacidosis is not valid. They demonstrated that insulin is needed in reduced amounts during fat burning, and it is not necessary to eat glucose at all (except to rescue hypo’s) if you are a fat-adapted Type 1.
The potential of fat stores to provide energy over extended periods in ketogenic-adapted individuals. Breath metabolic testing and blood ketones showed our bodies were fat-burning & working optimally. There was no ‘hitting the wall’ as we were tapping into a fat store that has ten times the energy capacity compared to total glycogen stores.
Dietary carbohydrate is not essential for human performance. Our liver can make all the glucose required for crucial cell functions, which was demonstrated by continuous glucose monitoring. A ketogenic diet (including essential fats and protein) puts the body into fat-burning mode and allows access to the reservoir of fat energy. All participants had stable glucose levels, including the two people with type 1 diabetes.
Unexpected findings were that participants experienced improved mood, mental clarity and focus. Furthermore, all participants maintained high levels energy. Some of them experienced minor musculoskeletal discomfort, but others had none at all.

Re-Thinking Diabetes

Through our research and experiences in training, and as proven in this event, we expect this project will help remove current obstacles that appear to be getting in the way of providing an option that will reduce the disease burden of diabetes (both T1D and T2D) and metabolic ill health. Some of the safety concerns holding back delivery of low carbohydrate lifestyles and fasting in healthcare settings have been answered.

Clinicians and people with diabetes on this project feel ketogenic diets should be a management option that can be delivered with skill: should a diabetic patient (T1D or T2D) decide to take up this option.