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What is the OPTIFAST 6 week plan?

Our 6 week plan has been developed by nutrition experts to help you lose significant amounts of weight. It is low in carbs and focuses on providing your body with nutritious whole foods, vitamins and essential minerals that you need every day.

How does our 6 week plan work?

  • For the first 3 weeks, simply replace all of your meals & snacks with 4 OPTIFAST products, providing you with approx. 800 calories and all the essentials that you need to support healthy weight loss.
  • For the next 3 weeks, you reintroduce normal wholefoods such as lean protein and vegetables, and your daily calorie intake gradually increases to between 1400 – 1700 calories.
  • At the end of 6 weeks, you move to our long-term Maintenance Plan where you follow a Mediterranean-style diet. You can also use one of our Intermittent Fasting Plans to help you maintain your weight loss.

Discover the 6 week plan

OPTIFAST have specially designed the below bundles to support you on your weight loss journey.
Six Week Plan FAQs

Our six week diet plan is split in to three phases. During phase one, all of your daily food intake is replaced with OPTIFAST products. This helps to limit your calorie intake to around 850 calories per day while ensuring you get all the vitamins and minerals you need. During phase 2, you begin to gradually reintroduce food back in to your diet, and slowly reduce the number of OPTIFAST products you have each day. Phase 3 is the maintenance stage- continuing your new healthier diet and lifestyle.


Phase 1 has been designed to provide you with approximately 800 - 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. During phase one of the six week plan, your protein intake will be about 80g 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.


Don't worry if you have a little bad breath or halitosis during phase one. Not everyone will experience this, but if you do it will only last whilst you are following the total diet replacement phase (phase 1). Chewing on sugar free chewing gum or even some fresh mint can be very effective in managing this. It is important also to maintain an adequate fluid intake. We recommend drinking 2 liters per day.


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 used as a total diet replacement 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.


We would encourage you to drink at least two litres or 8 glasses of calorie-free fluids per day.


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.


It's important to remember that everyone is different. The rate at which people lose weight can vary, and depends on other factors such as how active you are and how much you weigh. However, research has shown that many people find that their weight loss is quicker at the beginning of the programme (phase 1) and then slows down. This is normal.

During the six week plan, 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 reintroducing food gradually over a period of threeweeks, however you can follow a pattern that best suits you. In week 1 of transition, we recommend adding breakfast back in to your daily routine, and continue to replace your lunch and evening meals and a snack if needed with OPTIFAST (3 Optifast portions each day in total). In week 2 of the transition period, we recommend adding lunch back in to your daily routine, and continue to replace your evening meal with OPTIFAST (1 Optifast portion per day in total). In week 3 of the transition, we recommend adding your evening meal back in to your daily routine with none or 1 OPTIFAST product at this point if needed for a snack. The reintroduction of foods should begin with non-starchy vegetables and lean protein, low carbohydrate meals, targeting a total of 1400-1700 kcals/day.