A nutritionist shares her verdict on the controversial Cambridge Diet plan

It claims to help you lose weight, fast - but is it healthy or sustainable?

Cambridge diet: A woman chopping some green vegetables
(Image credit: Getty Images)

Sadly, as the annual pre-summer search for weight loss plans begins, diets like the Cambridge diet, Dukan diet, and cabbage soup diet - heck, even the Sirtfood diet - are back in the spotlight. 

While you know that every body is different, will look different, and will have a different set point when it comes to weight, you might be wondering which diets are actually good for you and which - well, aren't. 

While you should never feel pressured to change how you look, if you would like to lose a few pounds, the Cambridge Diet has long promised to help with just that.

That said, we're keen to make sure you're armed with expert advice before trying anything new. So, is the Cambridge Diet worth trying or a health-risking fad diet? 

Speaking to nutritionist Lauren Windas, the Cambridge Diet - recently renamed the 1:1 diet - is an extreme weight-loss plan, arguably overly restrictive. "You're putting your body into a very low-calorie deficit throughout much of the plan and entering starvation mode," she shares.

Based on a range of bars, soups, and shakes, this diet plan claims to be cheaper than Weight Watchers and help you lose weight faster than your average calorie-controlled diet.

But it's far from being all positive. Here's everything you need to know, according to the qualified expert.

Cambridge diet: a nutritionist's guide

What is the Cambridge Diet?

Despite the name, the diet bears no relation to the Duchess of Cambridge, Kate Middleton, according to Windas. "The Cambridge Diet was invented in the 1960s by Alan Howard, a Nutritionist at Cambridge University, hence the name," she shares. "Working in the Department of Medicine, he collaborated with a consultant at a local hospital, where they designed a low-calorie diet for morbidly obese patients. They later released this plan to the public in the 1980's."

The Cambridge Diet stipulates the regular consumption of low-calorie shakes, soups and snack bars, claiming they've been designed specifically for the program to fulfil all of your daily nutritional requirements under strict calorie guidelines, and further, that they can lead to pretty quick weight loss.

There are six variations of the Cambridge Diet, but all promise to pair you with a Cambridge Diet counsellor who follows your progress throughout.

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How does the Cambridge Diet work?

Similar to the keto diet, the Cambridge Diet works by forcing your body into a state of "ketosis."

This occurs when the body doesn't receive all of the calories it needs to function properly and so is forced to turn to fat stores in order to carry on.

What are the pros of the Cambridge Diet?

According to the nutritionist, in the short term, it can deliver quick results in terms of fat loss.

Plus, it’s fuss-free and convenient. "One of their consultants guides you, takes the thinking and planning away from you so it is easy to implement into your routine. It's also convenient for those who are time-poor or struggle with portion control."

What are the cons of the Cambridge diet?

Initially, when the diet launched in the 1980's, the daily calorie count consisted of a dangerously low 330 kcals per day, shares Windas. "In recent years, this has been upped to 600 kcals per day, and can go up to 1500 calories in some steps of the plan," she shares.

Nevertheless, she highlights that you are still putting your body into a very low-calorie deficit throughout much of the plan, even entering starvation mode.

It's important to know that there are much healthier ways to achieve your weight loss goal, she stresses. (Our expert-led fat loss tips explain how).

Further, because it's a short-term diet, many people may struggle to keep the weight off long-term, she explains. "It can provide quick results, however, what do you do when the plan ends?" she questions.

It's far from sustainable and doesn’t give you the tools to cement healthy habit changes while maintaining a healthy relationship with food.

Not to mention it's restrictive. "While the plan is not only low-calorie, it also involves consuming their specific meal replacement products which consist of shakes, smoothies and soups. Because the range is quite limited, those who follow the plan can easily become bored and feel deprived of the foods they love."

Reported side effects of the diet are bad breath, thinning hair, nausea, dizziness and diarrhoea.

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Does the Cambridge Diet work?

It's worth remembering that every body is different and so diets will work differently for, say, your best friend. Plus, you can't easily create this diet plan at home. If you do opt in, experts from the brand stress the importance of doing everything by the book.

That said, our nutritionist reckons that's a one-way ticket to disordered eating

There are six types to try including the weight plans you'll be looking at:

  • Sole Source: Eat 3-4 Cambridge Diet meal products each day (consuming 415-554 cals, lasting 1 week minimum/12 weeks maximum)
  • Sole Source +: Eat 3 Cambridge Diet meal products and 200ml of skimmed milk each day (consuming 615 cals a day, lasting 1 week minimum/12 weeks maximum).
  • Step 2: Eat 2 Cambridge Diet meal products plus protein-rich foods, skimmed milk and some vegetables (consuming 810 calories a day, lasting 1 week minimum).
  • Step 3: Eat 2 Cambridge Diet meal products plus skimmed milk, breakfast and salads for lunch and dinner (consuming 1000 calories for 2 weeks).
  • Step 4: Eat 2 Cambridge Diet meal products plus skimmed milk, breakfast, lunch and dinner (continue for 2 weeks).
  • Step 5: Eat 1 Cambridge Diet meal product plus skimmed milk, breakfast, lunch, dinner and snack (continue for 2 weeks).
  • Maintenance: Eat a healthy diet plus your choice of Cambridge Diet products (continue indefinitely).

"Far too expensive and not enough food." 

After a quick scan of the reviews on Review Centre, where several people have shared their own experiences of trying the diet, the resounding themes are that it's far too little food to function normally.

Others said that the consultants weren't as supportive as they'd hoped and didn't offer 24-hour support, as advertised.

Finally, one dieter said that she found it effective but far too expensive, pointing out that it'd be "impossible" for most people to spend £51.00 a week on the diet shakes, bars and products.

Is the Cambridge diet good for you?

Bottom line: low-calorie diets like the Cambridge Diet are not sustainable and won't work in the long term. Windas warns that you'll be putting both your physical and mental health at risk if you try the diet. "They very much fit into the category of a fad diet, and if your ultimate goal is weight loss, there are much healthier means of losing weight than following this diet," shares Windas.

Her advice? Don't buy into any diets that tell you you must buy their products in order to lose weight - because often, companies are simply profiting from people's lack of education about sensible weight loss.

Not only that but avoid any diets that promise immediate results. They're simply starvation branded and presented to you in another form.

What should you do, if you're keen to lose a little weight then? The expert recommends working with a nutritionist and adopting a sensible calorie deficit while making sure you're building balanced plates full of macronutrients (protein, carbohydrates and healthy fats). "This will provide you with unbiased, tailored and bespoke dietary advice to meet your personal health goals, and you achieve long-lasting healthy change in not only body composition but also in mind and general wellbeing," she shares.

Ally Head
Senior Health, Sustainability and Relationships Editor

Ally Head is Marie Claire UK's Senior Health, Sustainability, and Relationships Editor, nine-time marathoner, and Boston Qualifying runner. Day-to-day, she works across site strategy, features, and e-commerce, reporting on the latest health updates, writing the must-read health and wellness content, and rounding up the genuinely sustainable and squat-proof gym leggings worth *adding to basket*. She's won a BSME for her sustainability work, regularly hosts panels and presents for events like the Sustainability Awards, and saw nine million total impressions on the January 2023 Wellness Issue she oversaw. Follow Ally on Instagram for more or get in touch.