1. The Very Low Calorie Ketogenic Diet (VLCKD)

2. Calories & Kilojoules
Calories and kilojoules are units of energy associated with food
Calories and kilojoules are difficult to measure as a number of things affect energy availability, such as :
food preparation (chopping, dicing, raw, cooked etc.)
Health status
Daily requirements
Growth
Exercise status etc.
Calculating daily energy requirements via total daily energy expenditure (TDEE) is also highly problematic as the calculation is inflexible and unable to be varied for race, significant weight loss history or any other variable than exercise
The errors associated with energy calculations (both in food and TDEE) are so significant that it makes the process worthless
So why are we doing it?

3. Energy Calculations BMR Calculation (Harris Benedict 1984)
Men BMR = ( × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)
Women BMR = (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)
Mifflin St. Jeor Equation
For men: BMR = 10 x weight (kg) x height (cm) – 5 x age (years) + 5
For women: BMR = 10 x weight (kg) x height (cm) – 5 x age (years) – 161
Calculating Intake to maintain weight
Little to no exercise Daily kilocalories needed = BM% x 1.2
Light exercise (1–3 days per week) Daily kilocalories needed = BMR x 1.375
Moderate exercise (3–5 days per week) Daily kilocalories needed = BMR x 1.55
Heavy exercise (6–7 days per week) Daily kilocalories needed = BMR x 1.725
Very heavy exercise (2 x day, high intensity) Daily kilocalories needed = BMR x 1.9
TDEE = RMR + thermogenic influences (i.e. thermic effect of food) + energy associated with exercise
RDEE = (FFM kg) (McArdle, Katch & Katch, 2001)

4. When Calorie Counting Works
When energy intake is sufficiently low, fasting benefits ensue
However, calorie restriction must be short otherwise metabolism can be affected
Fasting is able to improve a number of significant health markers, very rapidly
Blood lipid profile
Glycaemic control
HbA1c in diabetics
Homocysteine
Inflammation (hs-CRP, ESR)
Waist circumference/Body composition
Hormone sensitivity
800 calories is able to induce these effects
REMEMBER: Calculating 800 calories is not an exact science so do not tie yourself up in knots trying to be spot on
REMEMBER: The number 800 is to give you a target more so than for any other reason (i.e. it would be hard to follow a low food diet)
REMEMBER: Energy intake simply needs to be very low

5. Very Low Calorie Diets
Very low calorie diets (VLCD) have been shown to have significant health benefits in the short term
They improve blood lipid profile, glycaemic control, blood pressure, waist circumference and more
VLCD induce ketosis which increases lipolysis
There are significant problems though
People are hungry (all the time)
Poor adherence rates
An increase in low fat, processed foods and shakes to try and stay full but keep calories low
Rebound weight gain for most people (hormonal dysfunction and loss of LBM)

6. Very Low Calorie Ketogenic Diet
VLCKD has been shown to be superior to the VLCD in a number of recent studies
Study by Moreno et. al. (2014) concluded that “The VLCK diet was well tolerated and the side effects were moderate and transitory. In a group of obese patients, the VLCK diet was significantly more effective than a standard LC diet. At one year follow-up in the group with VLCK diet, most of the patients loss more than 10 % of their initial weight and lean mass was well preserved.”
Study by Merra and colleagues (2016) concluded that “Our pilot study showed that a VLCKD was highly effective in terms of body weight reduction without to induce lean body mass loss, preventing the risk of sarcopenia.” They suggested that the mode of action lies in part, with the protein inducing high levels of satiety

7. Very Low Calorie Ketogenic Diet
VLCKD has a number of distinct advantages over the VLCD
Fat adaption which reduces hunger and makes adherence easier
Inclusion of full fat products which also ease hunger
Focus on adequate protein intake which increases satiety
Focus on unprocessed food
Greater improvements than the VLCD in
HbA1c
Glycaemic control
Blood lipid profile (TG:HDL)
Hormone sensitivity (insulin in particular)
Adherence rates
Long term success (preservation of LBM)
The ketogenic diet has been shown to be superior to the low fat diet across numerous markers so it makes sense that the low calorie ketogenic diet would also be more effective than the traditional low calorie (low fat) diet at improving health markers

8. How Long Should I Do the VLCKD?
It depends 
Weight loss history
Hormonal resistance
Exercise status
We recommend no longer than 4 weeks with a period of normal LCHF eating in-between. This is for two significant reasons
1. it’s tough going and difficult to stick to for long periods of time
2. protection of LBM and metabolic rate
The VLCKD can be cycled intermittently until desired weight loss is achieved

9. Rationale for the VLCKD
A significant number of women (in particular) do not respond to LCHF
If you understand that obesity is a metabolic/hormone disorder and not a caloric disorder then the focus for weight loss needs to be hormonal
Fasting is one of the best strategies for improving hormone sensitivity
Fasting can only be done intermittently
VLCKD can be done for weeks at a time and induce the same benefits as fasting
This is especially important for people who need to lose weight but have been unable to do so even when severely restricting calories
The ketogenic diet has different metabolic effects than traditional low calorie (i.e. low fat) and is able to preserve lean mass and therefore protect metabolic rate
VLCKD induces significant improvements in a number of health markers
VLCKD works well with adequate protein, high intensity exercise to preserve muscle mass and when done for short periods of time (or intermittently)

10. REMEMBER!!
800 calories is somewhat arbitrary but is associated with a sufficiently low intake of food to induce fasting benefits
Ensure your macronutrient ratios are in alignment with LCHF/keto
You don’t have to sit on 800 calories exactly – if you go over, it’s not a fail
If you feel jittery, shaky, unwell etc. then this is your body telling you to eat. DO NOT ignore these messages
You are not failing if you eat additional food on a particular day – you are successfully listening to you body
Weight loss is due to long term consistency (i.e. nothing gets undone or completely fixed in a day)
The end is near 

11. Research Goday et. al. (2016) Moreno et. al. (2016)
Gomez-Arbelaez et. al. (2016)
Brehm et. al. (2013)
Hussain et. al. (2012)
Bueno et. al. (2013)
Cicero et. al. (2015)