The 90 Day SSS plan from The Body Coach, Joe Wicks, helps users adapt a healthier way of living by mixing 15 minute bursts of high-intensity exercise with balanced meals.
The SSS plan, which stands for shape, shift and sustain, promises to help people shed excess fat and tone up, fast.
And - judging by some of the photos from those who have tried it - the results are pretty phenomenal.
In a nutshell, what is the 90 Day SSS Diet?
"The plan is a lifestyle change. It's tailor-made so anyone can follow it, no matter what their fitness or eating habits are," says Wicks.
"Clients fill out a questionnaire when they sign up to the plan. Height and weight, measurements, habits, all sorts of factors can affect the plan they receive.
"When it lands in their inbox they have a set meal and fitness plan that I guarantee, if followed, will work for them."
How does it work?
"Because each plan is bespoke, the calories and macronutrients in the set menu of recipes are individually tailored to each client’s personal energy demands," adds Wicks.
"If you look at other diets out there, they are always so restrictive – you can’t eat this, you can’t eat that, you can only have two calories a day!
"I get clients eating loads of really tasty food, it's just that it is the right food and the right balance when their body needs it.
"From an exercise point of view, I get all my clients doing High Intensity Interval Training (HIIT) straight away because it means you don’t have to spend hours in the gym - after all, people are busy."
He continues: "With HIIT training you repeat short bursts of high intensity exercise with timed rests which melts fat away.
"Later we add in short weight training sessions to help them gain muscle to show off alongside their leaner frames, which they achieve from all the HIIT work."
How did you come up with the idea for it?
"I was just so tired of people being on horrific calorie restrictive diets, taking in a tiny amounts of food per day, and expecting to lose weight and tone up," says Wicks.
"It is really sad that we've been conditioned to under eat, especially when trying to shape up, and that is something I really want to educate people about.
"I’d like to think that clients who have been on my plan would never, ever do a low calorie diet again as they‘ll have changed their attitudes towards exercise and understanding of food.
"My motto is, if you eat more of the right things, train harder and faster, you will burn fat and get lean."
What do clients typically eat on the diet?
"The diet runs on a 'pick n mix' principle, the only thing that is always a constant is that clients need to eat a carbohydrate refuel meal after their training session - whether they train first thing in the morning, during their lunch break or at night.
"A refuel meal could be anything from build-up bagels to quinoa porridge to steak and rice.
"I get clients eating loads of food - three meals and two snacks a day - and when they’re not loading up on their post-workout carbs there are lots of tasty low carb options to try, from curries to stir frys to omelettes."
He adds: "It never feels like a diet as there is so much food - it's just that it is the right food at the right time."
What are the benefits of the 90 Day SSS Diet?
"You know what, alongside shaping up and feeling great for it, I’m also really proud of the sense of community it has generated and the support that everyone offers one another," explains Wicks.
"I think it's right to celebrate my clients' achievements. They are proud to show off their bodies when they’ve worked hard - and so they should be!"
So, does it actually work?
Rachael, 27, who works in London is a size 8 and approached the plan as a way to maintain a healthy lifestyle rather than lose weight.
She tells HuffPost UK Lifestyle: "I’m not actually sure if I’ve lost any weight as I don’t have scales, but I feel much more toned and healthy, and my clothes fit better.
"I have cheated a bit, particularly with the some glasses of wine, but I’ve managed to do the exercise four times a week and the recipes he recommends are very tasty."
Rachael's plan costs her roughly £50 per month, which she believes is worth the money.
"I like the exercise part because it’s quick and you can do it at home or in the garden without equipment," she says. "Even if I’m really not in the mood I can persuade myself to do it, as it’s over so quickly.
"I’m also allergic to the gym so would prefer to do this than buy a gym membership. I work quite unpredictable hours, but I normally fit it in straight after work and before dinner."
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For Rachael, her main criticism is that the videos aren't always that professional.
"He sometimes misses repetitions or doesn’t warm down which is not ideal for a beginner if they aren’t paying attention," says the 27-year-old.
"There also isn’t a huge variety of recommended exercise videos, so he could add more."
She adds that the plan is about 80 pages long and most of that is dedicated to recipes, with about two pages devoted to exercising ("so it feels a bit brief").
"Also there is quite a bit about recommended supplements and protein powders, which I decided to ignore as that could add up price-wise and I’m not convinced supplements work."
But despite this, she adds: "All in all, I would recommend it!"
What the nutritionists say...
A spokesperson from The British Association for Applied Nutrition and Nutritional Therapy (BANT) tells HuffPost UK Lifestyle that they believe diet plans should be tailored to the individual "using functional and genetic testing to determine the best way forward".
Additionally, Dr Emma Derbyshire from Nutritional Insight reveals that the SSS plan might work, "however any plan that involves changing normal exercise, nutrition and lifestyle habits has potential to work".
"The best way to achieve a healthy weight is to follow healthy nutrition and exercise/physical activity practices that can be maintained for life," she explains.
"Simple changes such as swapping calorific drinks for water and reducing portion sizes can also go a long way."