Mechanics of a VLED

A VLED works by restricting total energy intake to approximately 800 calories (3300kJ) or less per day. Weight loss with a VLED is achieved by restriction of both carbohydrate and total energy intake. This enables the body to use its body fat stores for energy via a metabolic process called ketosis.

Ketosis is a metabolic reaction that occurs when following the OPTIFAST VLCD Program Intensive level. When glucose is in short supply, ketones are produced which provide an alternative fuel source derived from fat¹.

A diet containing 50-70g carbohydrates is generally considered low enough in carbohydrates to produce ketones, but there is no absolute level that guarantees ketone production. The amount of carbohydrates required to induce ketosis depends on several factors. It can be individual and can vary from day to day depending on activity levels, fluid intake and other factors.

The term "ketones" refers to three compounds:

Acetoacetate (AcAc)
3-β-hydroxybutyrate (BHB)
Acetone

The circulating level of ketones in the body at any one time is dependent on their rate of production and rate of utilisation. Acetoacetate and 3-β-hydroxybutyrate are the two primary ketones generated and used for fuel under low carbohydrate conditions. Acetone gives the characteristic odour to the breath of patients in ketosis, similar to that of nail polish.

Dietary ketosis used in the management of weight loss should not be mistaken for ketoacidosis. Dietary ketosis is a controlled, insulin-regulated process which results in a mild release of fatty acids and ketones into the circulation in response to a low carbohydrate intake. Ketoacidosis, on the other hand, is a condition in which abnormal quantities of ketones are produced due to no insulin regulation of ketone levels. To reach a state of ketoacidosis, the body has to be in a stage of not producing any insulin. This is why ketoacidosis is generally only seen in uncontrolled type 1 diabetes.

Level of circulating blood ketones for different conditions²

	Blood Ketone Level
Weight loss using a VLED and inducing mild ketosis	0.3-0.7mmol/L
Refractory paediatric epilepsy	2.0-7.0mmol/L
Diabetic ketoacidosis	>3.0mmol/L, can be as high as 25mmol/L

Once the body is in ketosis, any excess ketones that the body does not use for energy, are excreted via the urine and breath (thus the incidence of halitosis in some cases). Measuring ketone levels on the breath or in the urine can be used as a guide to assessing compliance. Confirm your patient suitability to start the program.

References
1. Gibson, A.A., et al., Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes Rev, 2015. 16(1): p. 64-76.
2. National Health and Medical Research Council., Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults, Adolescents and Children in Australia. National Health ad Medical Research Council, 2013.

Overview of Very Low Energy Diets

Very Low Energy Diets (VLED), also known as Very Low Calorie Diets (VLCD) have been shown to be very effective in the management of obesity, with weekly weight losses averaging approximately 1.0 -2.5kg per week, providing greater initial weight loss than other forms of calorie restriction.
Expected rate of weight loss on Intensive Level

During the Intensive Level of the OPTIFAST Program, weight loss averages 1.0 to 2.5kg/week with an average total loss of 20kg after 12 to 16 weeks.
Long term weight loss goals

It is often mentioned in the lay press and amongst healthcare professionals that "the faster you lose weight, the quicker you regain it", yet there is little evidence to support this assumption and in fact the opposite may be true.
Mechanics of a VLED

A VLED works by restricting total energy intake to approximately 800 calories (3300kJ) or less per day. Weight loss with a VLED is achieved by restriction of both carbohydrate and total energy intake. This enables the body to use its body fat stores for energy via a metabolic process called ketosis.
Patient suitability

For a patient to succeed with the OPTIFAST VLCD Program, it is important to assess their readiness to undertake the necessary behaviour changes required for effective weight management.
Calculating ideal body weight

Ideal body weight is calculated to help determine an appropriate weight for height or to determine a long term weight loss goal. We recommend that you use the ‘Adjusted Ideal Body Weight’ calculation.
Calculating protein requirements

OPTIFAST VLCD is formulated to contain adequate high quality protein in sufficient quantities for nitrogen sparing and to preserve lean body mass.
Medical monitoring

As a healthcare professional, you can tailor the program to suit your patient's specific needs.
Long-term weight management with the OPTIFAST VLCD Program

Research has shown that having the support and guidance of a healthcare professional will make the program more successful for your patients.
Bariatric surgery and the OPTIFAST VLCD Program

Surgical intervention by way of bariatric surgery can result in substantial weight loss that is sustained over the long term when combined with education, ongoing monitoring and patient support.
Diabetes and the OPTIFAST VLCD Program

Most overweight and obese patients with Type 1 or Type 2 diabetes are eligible to use OPTIFAST VLCD as part of an overall management program that emphasises the importance of ongoing weight maintenance.
References