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Do not go on the Optifast VLCD if you are/ have:

A Very Low Calorie Diet (VLCD) or the Intensive phase should never be used by normal weight individuals because it may lead to excessive loss of lean body mass. If your BMI is under 25kg m2 we would recommend that you consult an Accredited Practicing Dietitian for a suitable weight management plan or consider following either the transition or maintenance phase.

OPTIFAST VLCD Program is not recommended during pregnancy for a number of reasons. The low carbohydrate content is designed to induce ketosis (fat breakdown) which leads to ketones in the blood. Although the level of ketones is fairly low, the effect on the fetus is unknown. In addition, the OPTIFAST VLCD Program is not designed to meet the increased nutrient requirements of pregnancy (e.g. protein, iron and some B group vitamins).

The Intensive phase of the OPTIFAST VLCD Program (replacing all 3 meals with OPTIFAST VLCD products) is not recommended for women who are breastfeeding as it is not designed to meet the increased nutritional demands of lactation. If you are breastfeeding, you may start on the Maintenance phase (i.e. with replacing one meal per day with an OPTIFAST VLCD product). You can gradually increase the amount of meals replaced once your baby has started to wean off breast milk and is also consuming a reasonable quantity of solids. Fatigue is obviously a problem when you're breastfeeding so reducing your calorie intake too much can make this worse as well as affect your milk supply.

VLCDs are not recommended for growing kids; however, there may be children in whom severe obesity is resistant to other treatments. In such individuals the risks associated with obesity should be weighed against the risks of using a VLCD and should only be prescribed and monitored by a qualified healthcare professional.

Porphyria is the umbrella term for a group of rare disorders that involve a particular molecule called ‘haem’. Haem contains iron and is used in metabolic processes throughout the body. Porphyria occurs when the body cannot convert naturally occurring compounds (called ‘porphyrins’) into haem. While all tissues have haem, those that use it the most are the red blood cells, liver and bone marrow. Porphyria can affect the skin, nervous system and gastrointestinal system, depending on the specific type. Porphyria is contraindicated with OPTIFAST VLCD as extreme calorie restriction can provoke an acute attack.

If you have recently suffered from a Myocardial Infarction (Heart Attack) or have been diagnosed with Unstable Angina (Chest Pain) we recommend that you consult your doctor or cardiologist to determine whether the OPTIFAST VLCD Program is suitable for you.

Persons with advanced liver or renal disease are not suitable for the OPTIFAST VLCD Program, as they may require altered intakes of electrolytes and nutrients.


Precautions may need to be taken when using the OPTIFAST VLCD Program if any of the following pertain to you:

  • Age >65 years
  • History of severe psychological disturbance, alcoholism or drug abuse
  • Cholelithiasis or past history of gall stones
  • Pancreatitis
  • Fertility issues

It is essential that you seek the advice of a qualified healthcare professional who can help manage and advise you on which phase of the OPTIFAST Program is right for your weight management needs.


There are no active ingredients in the OPTIFAST VLCD products that will directly interact with any medications.

It is mainly that the weight loss process can affect the efficacy of some medications and some medications will impact your weight loss goals. Therefore, if you are on any medication it is very important to consult your doctor prior to commencing the OPTIFAST VLCD Program

Potential Side Effects

OPTIFAST VLCD is accepted as being a safe form of weight loss with only minor, transient side effects being observed. These side effects are a result of the rapid weight loss and Ketosis and may include: sensitivity to cold, halitosis (bad breath), headache, hair loss, irritability, postural hypotension, fatigue, muscle cramps and menstrual disturbances. These side effects are generally insufficient in magnitude or duration to warrant cessation of the program.

As with any major dietary adjustment, the first few days on the OPTIFAST VLCD Program can be difficult and are commonly known as the ‘3 Day Challenge’. As the body transitions into ketosis, you may experience some transient side effects such as fatigue, hunger, lack of concentration, nausea and headaches. Typically, only mild ketosis occurs during the OPTIFAST VLCD Program and most symptoms pass by in 4-6 days.

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