14th April 2026

The Very Fast 800 vs The Fast 800 Keto: What is the difference and which is right for you?

The Very Fast 800 and The Fast 800 Keto are two effective methods to help you lose weight quickly, and keep it off for good. Both have their benefits, and there are a few key differences between them so it’s important to understand how they differ if you want to decide which is right for you.

Keep reading to find out the differences between The Very Fast 800 and The Fast 800 Keto, and decide which method is right for you.

The Very Fast 800: The Basics

  • What is it? A diet plan that involves consuming around 800 calories per day of a moderately low-carb Mediterranean-style diet. It should be followed for up to 12 weeks, or until you’ve achieved a healthy weight, whichever happens first.
  • How does it work? Consuming 800 calories per day is considered a ‘fasting day’, which can put the body into a mild state of fat-burning ketosis. The lower calorie approach, combined with mild ketosis, leads to effective weight loss.
  • What do you eat? Plenty of protein, fibre and healthy fats, and a moderately low amount of carbohydrates. Take a look at these recipes to see the kinds of meals you can enjoy on The Very Fast 800.
  • Who is it for? The Very Fast 800 is highly effective for those who want to lose weight rapidly, or kickstarts a longer term health journey. It is also effective for those combating insulin resistance or type 2 diabetes.

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The Fast 800 Keto: The Basics

  • What is it? The Fast 800 Keto builds on the scientific foundation of The Very Fast 800 by reducing the carbohydrates further to push your body into a more consistent state of ketosis. It involves consuming 800-1000 calories per day and should also be followed for a maximum of 12 weeks.
  • How does it work? The Fast 800 Keto ‘flips the metabolic switch’ to achieve a state of ketosis. This is where your body burns fat stores as fuel, rather than glucose which is most readily found in carbohydrates.
  • What do you eat? Plenty of protein, fibre and healthy fats, and very little carbohydrates. Visit The Fast 800 Programme, or see here, for keto-friendly recipes.
  • Who is it for? This plan is for those who have a lot of weight to lose, quickly. It is particularly beneficial for those who want to target visceral fat, improve gut health or reverse metabolic syndrome.1 2 3

The key differences

Although there are some similarities to both approaches, there are a few key differences between them. These include:

  1. Calorie intake: The Very Fast 800 involves consuming roughly 800 calories per day, either through three small meals or or two larger meals with a good amount of non-starchy vegetables on the side (no need to count the calories for these). The Fast 800 Keto involves slightly more calories, allowing around 1000 calories per day – these are often made up by an extra scoop of Greek yogurt or a drizzle of extra virgin olive oil.
  2. Carbohydrate intake: The Fast 800 Keto is low-carb to achieve nutritional ketosis, while The Very Fast 800 focuses on a moderately low-carb Mediterranean-style approach.
  3. Speed of results: The Fast 800 Keto, while challenging for some, can result in more immediate weight loss results. The Very Fast 800 still achieves rapid weight loss, but at a slightly less accelerated pace.
  4. Differing challenge: While both approaches require an element of discipline and motivation, The Fast 800 Keto diet can be more challenging as meal options may be considered more limited.
  5. Side effects: Like a traditional ketogenic diet, The Fast 800 Keto may come with a few side effects, known as ‘keto flu’. This can include headaches, insomnia, nausea and dizziness.4

How to know which is right for you

We know everybody is different: what works for one person might not work for you, so think about your goals and your current lifestyle.

The Fast 800 Keto is for you if you are highly ambitious and motivated. Though it can be a more challenging approach to weight loss, it is rewarding in its more immediate, and often increased, results. It is also ideal if you are interested in achieving a consistent nutritional ketosis.

The Very Fast 800 may be more suitable to you if you are new to low calorie diets, as it will kickstart your journey towards weight loss in a slightly less restrictive way than The Fast 800 Keto. Because it is less restrictive, it is also more adaptable around existing routines if you have family, social or work commitments to factor in.

If neither sounds right for you, and you’re looking for something more flexible then we recommend trying The 5:2™ Diet. This approach involves fasting just two days a week and achieves weight loss at a steadier pace. To find out more, head here.

All three approaches, plus our long-term Way of Life plan, can be followed easily and enjoyably with The Fast 800 Programme. Sign up for your 7-day free trial to explore helpful meal plans, tasty recipes, automated shopping lists, an exclusive Community and more, all of which can guide you through whichever plan suits your goals best.

References

Volek J, Sharman M, Gómez A, Judelson D, Rubin M, Watson G, Sokmen B, Silvestre R, French D, Kraemer W. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutr Metab (Lond). 2004 Nov 8;1(1):13. doi: 10.1186/1743-7075-1-13. PMID: 15533250; PMCID: PMC538279.

Dowis K, Banga S. The Potential Health Benefits of the Ketogenic Diet: A Narrative Review. Nutrients. 2021 May 13;13(5):1654. doi: 10.3390/nu13051654. PMID: 34068325; PMCID: PMC8153354.

Paoli A. Ketogenic diet for obesity: friend or foe? Int J Environ Res Public Health. 2014 Feb 19;11(2):2092-107. doi: 10.3390/ijerph110202092. PMID: 24557522; PMCID: PMC3945587.

Bostock ECS, Kirkby KC, Taylor BV, Hawrelak JA. Consumer Reports of “Keto Flu” Associated With the Ketogenic Diet. Front Nutr. 2020 Mar 13;7:20. doi: 10.3389/fnut.2020.00020. PMID: 32232045; PMCID: PMC7082414.

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