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What Is The Cambridge Diet And Is It Safe?

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Last updated on September 5th, 2021 at 11:52 AM

From Dukan and ‘teatoxes’, to 5:2 and Keto, keeping up with diet trends can be a tricky business. One minute we’re being told to nix carbs completely, and the next we’re all eating like cavemen (in the case of the Paleo craze).

One of the hottest diet trends right now – the Cambridge Diet (or Cambridge Weight Plan) – claims it can help dieters shed weight faster than most other plans, thanks to its extremely low calorie limit.

But is it safe, are there any side-effects, and will the weight stay off long-term?

What is the Cambridge Diet?

Promising fast and effective results, this rapid weight-loss plan advocates regular consumption of meal replacement shakes, soups, porridges and snack bars, designed to fulfil all of your daily nutritional requirements, while cutting out hundreds of calories.

The plan actually dates back to the 1960s and was devised by biochemist Dr Alan Howard at Cambridge University (hence the name) and its profile has been rising in recent years – before really gathering steam in late 2017, thanks to social media platforms like Instagram and Pinterest.

By following its strict rules, it claims it can help dieters lose up to a stone a month, without depriving them of important nutrients or protein to keep lean tissue; a factor that’s often overlooked in other extreme dieting methods, like juicing and fasting.

How does it work?

There are a total of six variations of the plan, ranging from 440 to 1,500 calories a day, depending on factors such as your starting weight and weight-loss goals. Step one, or ‘Sole Source’, is the most austere, asking dieters to cut out all ‘normal’ daily foods and solely eat from Cambridge Weight Plan’s own-brand, low-calorie range of products, along with 2.5-litres of water.

Later stages – like step six, or ‘Maintenance’ – are more flexible, allowing room for some healthy foods/meals, interspersed with a few meal-replacements. So, you start at step one, and then slowly introduce solid foods as you begin to shed weight.

The idea is that you eat so few calories that your body is forced into a state of ‘ketosis’, where it starts to burn fat stores as a survival method. In this metabolic state, most of the energy supply of the body comes from ketone bodies in the blood, rather than glucose.

Because of this, the weight tends to fall off Cambridge Dieters rapidly – but as it involves eating less than 1,000 calories per day, experts warn that it should not be followed for more than 12 continuous weeks.

The plan comes with guidance and supervision

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Always speak to your doctor before making any extreme changes to your diet (Thinkstock/PA)

As it’s extreme, this diet is not to be entered into without supervision, and some steps might even require written consent from your doctor.

You can only get your hands on the products – which typically cost around £2.40 per meal – by meeting with a Cambridge Weight Plan consultant, who will take your weight and measurements and design a programme which fits your needs, as well as providing regular one-to-one meet-ups to help track your progress.

What is a typical day’s food like?

Millennials are apparently flocking to the programme, sharing their Cambridge meals while looking for inspiration on Instagram and Pinterest from others on the same journey.

At stage one, a typical day on the diet could include a strawberry shake for breakfast, a banana shake for lunch, and chicken and mushroom flavoured soup for dinner.

Step three again mixes the Cambridge Weight Plan meal replacement products with a 150kcal breakfast, a salad lunch of green leaves, a 400kcal dinner, plus 200ml skimmed milk and at least four pints of fluids.

As the diet progresses to the later stages, dieters can introduce coffee and tea, and low-calorie meal ideas like Vietnamese prawn curry, roasted ratatouille and cod fillet with poached egg and asparagus.

Is it safe?

Under one-to-one supervision from one of their trained consultants, the Cambridge Diet claims to be safe and healthy to follow, but some experts and nutritionists say they do not recommend diets restricted to under 600 calories per day.

Max Bridger, a personal trainer from LDN Muscle (, says: “It’s not something I would recommend to any of my clients. Sure, eating under 500 calories for 12 weeks will make you drop weight fast, but you’ll also lose a lot of muscle too – so don’t expect an athletic, toned physique at the end.”

Female feet on weight scale
Critics say it’s not a suitable method for keeping weight off long-term (Thinkstock/PA)

Due to the highly-restrictive nature of the diet, critics also say it does not equip dieters for long-term weight-loss. “Don’t expect to keep the weight off when you return to normal eating,” says Bridger. “You may put the weight you lost while on the Cambridge Weight Plan back on, once finished and returned to your normal lifestyle, as your metabolism will likely have adapted to the restricted calories by slowing down.

“Ketosis is a state not many people will realistically achieve either,” he continues. “As well as being very tough to achieve, ketosis is easy to lose, and comes with side effects like bad breath, digestive discomfort, nausea and even hair thinning in some cases.”

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You may suffer hair-loss on the Cambridge Diet, according to PT Max Bridger (Thinkstock/PA)

The bottom line, Bridger says, is that extreme weight-loss plans are not something everyday people should really utilise, as there is nothing to prevent rebound weight gain. “If you do opt for something like the Cambridge Diet, you certainly do not need to spend money on very expensive foods and shakes to help you eat the bare minimum calories to function,” he adds.

Before making any extreme changes to your diet, you should always speak to your GP to discuss any potential concerns or side effects.