We are often asked about how long you can stick to 800 calories a day for. In a rapid weight loss phase, where you stick to around 800 calories a day, every day, we encourage recipes which have been balanced with a variety of foods to ensure that you are getting adequate protein, fat, fibre and carbohydrates. To kick start weight loss, we recommend doing this for a minimum of two weeks and then see how you are doing.
The 800-calorie rapid weight loss phase is safe for most individuals for up to 12 weeks, as long as you stick to our recommendations, drink plenty of water and use a multivitamin. We would also recommend that after 3 months, you start introducing non-fasting days each week using the Mediterranean style diet, and move to an intermittent fasting regime.
As with any rapid weight loss diet, speak to your doctor first, particularly if you have a medical condition or are on medication. Remember, if at any stage you reach a BMI that falls in the underweight category, you must stop the diet immediately.
What does the science say about continuing on the 800-calorie plan?
Other rapid weight loss regimes, like the Cambridge Weight Plan, which starts people off with consuming 500-600 calories a day in the form of shakes and meal replacement bars before moving onto real food, recommends doing it for a maximum of 12 weeks. People have been doing this for over 30 years.
In the DIRECT study, where 298 patients with type 2 diabetes were randomly allocated to either going on a rapid weight loss regime or standard care, those on the rapid weight loss side of the study were asked to consume around 800 calories a day, mainly in the form of meal replacement shakes, for 3–5 months. This was followed by gradual food reintroduction and structured support for long-term weight loss maintenance. This weight loss regime was supervised by nurses working in a general practice setting. The main side effects found were headache and constipation.
One thing to be cautious of is that some women report hair loss after long term or repeated bouts of rapid weight loss. According to Professor Susan Jebb of Oxford University this usually happens about 3 months after starting rapid weight loss. It is temporary and when you increase your calories the hair will re-grow again, so there is no reason to be worried that this will be a long-term problem.
How do I move to the 5:2 or a Med Style plan?
For more support in implementing a Med-based 5:2 plan then consider The Fast 800, which can be tailored to your preferences.
What if I want to stick to a 800 calorie a day plan?
If you have been following a 800 calorie plan for the last 3 months and want to continue on the plan, we recommend that you speak to your health professional first and make sure that you get the all clear from them. Whilst you continue on the plan it is important to touch base with your usual health professional on a regular basis. Remember, as soon as you reach a healthy BMI, it is important to switch to either the 5:2 plan or the Med Style plan. If you ever reach a BMI that falls in the underweight category, you must stop the diet immediately.
When else may the 800 calorie a day plan be useful?
Whilst we don’t recommend that you continue to follow the 800 calorie a day plan over a prolonged period of time, the 800 calorie plan might be useful to re-implement from time-to-time if you feel that you have ‘fallen off the wagon’. For example, if you come back from holiday and want to kick start the diet again, you may decide to do the 800 calorie a day plan again for a couple of weeks to get things back on track.