Jacqueline Whitehart, author of the 5:2 Fast Diet Recipe Book, knows this of course, which is why her new diet book was released this week, just in time for a ‘new year, new you’.
Claiming that her previous diet had become too “difficult” to fit into her lifestyle anymore, Whitehart told Daily Mail she’d developed a new diet over two years that participants would lose weight following without the days of fasting.
It's called the Metabolic Fat Loss Diet Plan and it involves four alternating phases over 28 days: Detox and De-stress, Protein and Healthy Fats, Better Carbs and Balanced Eating.
After an initial four days of eating reduced-calorie meals with a ratio of 50 per cent energy from carbohydrates, 30 per cent from protein and 20 per cent from fats, followers will alternate between the Protein and Healthy Fats and Better Carbs phases for three days at a time.
The Protein and Healthy Fats phase balance is: Carbs: 20/Protein: 40/Fats: 40 which doesn't allow for much fruit or dairy. Whereas the Better Carbs phase allows for fruit and even dark chocolate with a ratio of Carbs: 40/Protein: 40/Fats: 20. Finally, participants end with a more relaxed Balanced Eating phase to set them up to follow healthy eating patterns once the diet ends.
Whitehart claims that her diet is more "realistic and doable" than the 5:2 Diet and that alternating the four phases "shocks your metabolism into burning fat more efficiently".
So will it actually work?
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To find out we spoke to accredited practising dietitian and Nourishing Bubs founder Olivia Bates, who said there was some merit to the diet, but it still contained areas of concern.
"In terms of diets, there are some shockers out there and I really don't think this one's it, but I guess the major thing with anything like this is the ability to maintain it afterwards," the nutritionist said.