Frequently Asked Questions

Ketosis is a metabolic reaction that occurs in your body when following the OPTIFAST VLCD Program Intensive Level. This means your body shifts from using primarily carbohydrates to using fats as an energy source, resulting in a reduction of body fat stores.

Ketones provide an alternative fuel source derived from fat when carbohydrates are in short supply. It has been suggested that ketosis may suppress appetite, which helps make following the OPTIFAST VLCD Program Intensive Level much easier. As the Intensive Level causes only a mild ketosis, it is a safe approach to weight loss.

Prior to the transition into ketosis, you will most likely feel hungry and you may experience some side effects such as:

• Fatigue                                                                                                                                                                                  
• Lack of concentration                                                                                                                                                         
• Nausea                                                                                                                                                                     
• Headaches

These side effects should only last about 3 days and most symptoms usually pass by days 4-6. This is what we refer to as the ‘3 day challenge’. Following the initial 3-day challenge, you will experience an increase in energy and reduction in appetite, which, in the Intensive Level, will result in consistent and successful weight loss. It is important to know that these are typical symptoms and you should try to stick to the program as prescribed or otherwise you will simply pro-long these uncomfortable first few days of the OPTIFAST VLCD Program.

Of course, if you are concerned about your symptoms or if they persist, speak to a healthcare professional such as your doctor, dietitian or pharmacist as they can advise how to overcome or correct these symptoms before coming off the program.

The amount of carbohydrate required to induce ketosis depends on a number of factors and can actually vary from day to day depending on activity levels and fluid intake. A diet containing 50-70g carbohydrate is generally considered low enough to produce ketones but there is no absolute level that guarantees ketone production. The OPTIFAST VLCD Program will keep your carbohydrate intake to below 70g per day and generally only produces a mild ketosis.

Once your body is in ketosis, any excess ketones that your body does not use for energy are excreted via your urine and breath (thus the incidence of bad breath in some cases). Measuring ketone levels can be used as a guide to assessing compliance. It is not compulsory to measure ketone levels but some people may find it useful. Ketones can be measured via urine, breath or blood. Also monitoring symptoms and side-effects can also be a good indication of whether you are in ketosis.

You can measure your ketone levels in your urine with Ketone Reagent Strips or Ketostix. The OPTIFAST VLCD Intensive Level only causes a mild ketosis therefore urine ketone levels will only show approximately 0.5-1.5mmol/L. Urinary ketone levels can be higher early on in the program so can be a good initial indicator of compliance however levels excreted in the urine decrease as the body starts to use more of them as energy. If you are losing weight steadily, then there is no need to be concerned. You can rely on the other symptoms of ketosis such as a reduction in your appetite and change in your breath as a guide instead.