The Fast 800 diet is a rapid weight loss plan which claims you can lose a stone in 21 days. The diet has been around for several years but has come back into the spotlight following a Channel 4 programme which follows several people who embark on losing a stone in three weeks.
Dr Michael Mosley’s Fast 800 diet markets itself as a ‘lifestyle plan’ that can allegedly make you lose a stone in 21 days.
The doctor, who created the popular 5:2 diet, and his wife Dr Claire Bailey are behind the show which was made in lockdown.
The Fast 800 diet is explained on its official website, which says the diet works by ‘flipping the metabolic switch’.
The site explains: “Your body is like a hybrid car; it runs on two different fuels – sugar and fat.
“When your body needs a quick burst of energy, the first fuel source it turns to is the glucose in your blood.
“Next it will draw on the sugar stored in your liver and muscle. Only when this starts to run low does the body turn to its fat stores.
“Your body can’t just burn fat. Instead it turns some of your fat stores into ketone bodies, which its uses as energy. The buildup of ketones in your blood is called ketosis.
“When you are on a low calorie diet (800 calories a day) you will begin to rapidly use up your fat stores.
“The first fat to go will be that around your gut, the visceral fat. This is also the most unhealthy fat.
“Because The Very Fast 800 plan is also moderately low in carbohydrates, this will add to the fat burning.”
The Very Fast 800 plan uses Mediterranean-style ingredients to keep you feeling fuller for longer, but also recommends using multivitamins to ensure you are staying healthy – which may ring alarm bells for some.
While the evidence suggests that an intermittent fasting diet may be an effective way to lose weight, it is unlikely to be more effective for weight loss than traditional methods of dieting.
The NHS website stipulates that very low-calorie diets should only be used on those who are obese or severely obese and need to lose weight rapidly.
The website reads: “Very low calorie diets should only be followed under medical supervision for a maximum of 12 weeks.
“Do not follow a very low calorie diet unless a GP has suggested it to you.
“They are not the first option to manage obesity and should not be routinely used.”