In order to lose weight, we need to take in less energy in the form of calories than we burn off. By taking in around 800 - 850 calories each day, most people will achieve a significant energy deficit which helps to promote weight loss. The OPTIFAST diet replacement approach provides fewer calories whilst still providing all the micronutrients you need than some other approaches to weight loss, and is usually followed for a shorter period of time.

During the programme, the number of calories you take in reduces significantly compared to your usual diet. For this reason, it can be normal to experience some tiredness, headaches, nausea, or light-headedness. This tends to settle down as your body adjusts to the programme. However, if you experience severe or persistent symptoms, always make sure you seek medical advice.

We recommend you spend around 3 months on this plan. After this time has passed you can continue with the Maintenance plan.

Everyone is different when it comes to weight loss. How much and how quickly you lose weight depends on many things, including how much you weigh, how active you are, and how many calories you are taking in each day. On our intermittent fasting diet plan, weight loss is expected to be more gradual than with our continuous six week plan because overall you will be taking in more calories each week. Your rate of weight loss should increase the more days you follow intermittent fasting diet plan.

If your new diet contains a very different amount of fibre compared to what you are used to, it is possible to experience some digestive changes such as a change in bowel habit, bloating, or flatulence. As you adjust to your new plan this should settle down. If you experience persistent, severe or worrying symptoms, we advise you to seek advice from your GP.

When using the intermittent fasting plan Optifast provides all the nutrition you require, and there should be no need to take additional supplements. If you have a diagnosed deficiency or take prescribed vitamin or mineral supplements, we recommend you speak to your GP to decide if you need to continue these.

Optifast days on the intermittent programme will provide you with approximately 850 calories each day. This low calorie intake is to support you to lose weight. By taking four products from the Optifast® range each day, you will also receive all the vitamins and minerals you require.

Optifast® products are high in protein. On the fasting days, your protein intake will be between 70 and 81g of protein per day, depending on the combination of products you choose.

Yes, including tea and coffee is fine, but during phase one remember not to have them with milk, sugar or syrups which will provide additional calories.

Alcohol is not recommended as it can place extra strain on your liver and kidneys. Alcohol also has a diuretic effect and contains extra calories which could slow down your weight loss. Try to choose calorie-free drinks instead, such as tea (without milk), or soda water with a spritz of lemon or lime.