What is the Cambridge Diet plan? Here's whether the eating regime works for weight loss

The Cambridge Diet plan promises to help you slim down—but does it work?

A healthy meal as part of the Cambridge Diet Plan
(Image credit: Getty Images)

The Cambridge Diet plan, now renamed the 1:1 Diet by Cambridge Weight Plan, is one of the many eating regimes promising to help you slim down and stay there in a record amount of time. 

No one should feel pressured to lose weight, whether for a particular event or a seasonal holiday. But if you do want to drop a few pounds, it's important to have the best information out there on popular diet plans. 

So whether you're wondering whether the Cambridge Diet works for creating a calorie deficit to lose weight or you just want to know what you can eat on it, we've enlisted advice from nutritionist Jenna Hope (opens in new tab) to lay down what you really need to know before trying out this restrictive diet plan. 

What is the Cambridge Diet plan?

The Cambridge Diet was created by biochemist Dr Alan Howard, who worked at the Dunn Nutrition Laboratory in Cambridge (hence the name), and his partner Dr Ian McLean-Baird, a consultant at a local hospital. They launched the plan in 1984 as a weight-loss method for those who were clinically obese. In recent years, it has become known as the 1:1 Diet by Cambridge Weight Plan. 

The plan is based on a range of low-calorie shakes, soups and bars that you buy from the company and supposedly have a complete nutritional profile, designed specifically for immediate weight loss. Similar plans include the Jane Plan and other weight loss meal delivery services.

Within the 1:1 diet, there are six different variations you can follow. It starts with step one (or 'Sole Source'), which is essentially a very low-calorie diet, where you only eat the range of foods sold by Cambridge Weight Plan, all the way through to step six (or the 'Maintenance'). This is a healthy diet combined with meal replacements at points, depending on how quickly you want to lose weight and how much you want to lose. 

After you sign up, to help you along the way, you're assigned a Cambridge Diet counselor to follow your weight loss journey from beginning to end. 

  • Step One ('Sole Source'): Three to four Cambridge Diet meal products per day, working out to around 415-554 calories, for between one to 12 weeks.
  • Sole Source +: Three Cambridge Diet meals and 200ml of skimmed milk per day, which is around 615 calories, for between one and 12 weeks. 
  • Step Two: Two Cambridge Diet meals plus protein-rich foods, skimmed milk, and some vegetables. This works out to about 810 calories a day, which you continue for between one and 12 weeks.
  • Step Three: Two Cambridge Diet products, along with skimmed milk, breakfast and salads for lunch and dinner, working out to about 1000 calories. You follow this for two weeks. 
  • Step Four: Two Cambridge Diet meals, along with skimmed milk, breakfast, lunch and dinner. For two weeks.
  • Step Five: One Cambridge Diet meal product. Along with skimmed milk, breakfast, lunch, dinner and a snack, for two weeks.
  • Step Six: A healthy diet, with Cambridge Diet products as supplements. Continued indefinitely.

How does the Cambridge Diet work and what can you eat?

During Step One of the plan, also known as the ‘Total Diet Replacement Step’ you will consume a minimum of 600 calories a day in the form of three or four meal replacement products from the plan. Once the first stage is complete, your daily allowance steadily increases as you move up through the steps and begin to reintroduce normal foods back into your diet. 

How it intends to offer fast weight loss results is, similar to plans like the ketogenic diet, the Cambridge Diet pushes the body into an intense calorie deficit. This is where you burn more calories every day, through simple acts like breathing and sleeping as well as exercise, than you eat. This is typically achieved through eating fewer calories throughout the day and increasing the amount you exercise. 

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Is the Cambridge Diet effective?

This will entirely differ from person to person as every body is different. However, generally, if you eat within a calorie deficit then you will begin to lose weight. While you can get into a calorie deficit via lots of different methods, including restricted eating on the Cambridge Diet Plan, according to a leading study by the University of Vienna (opens in new tab), it's the only method that actually works for weight loss.

And the higher your deficit, the more weight you'll lose, which is why extremely low-calorie plans like this are promoted for fast weight loss. 

"In extreme circumstances, some GPs may recommend a very low-calorie diet to support weight loss, however, it is unlikely to be sustainable and is not considered a particularly healthy way to lose weight. In such cases, ensuring you’re working with a healthcare professional is vital," nutritionist Jenna Hope explains. 

"The Cambridge Diet is a very low-calorie diet which promises fast weight loss. However, very low-calorie diets can be unsustainable and can alter physiological function which in turn may affect weight regain," she adds. 

"Evidence from the University of California (opens in new tab) has suggested that low-calorie diets can increase appetite hormones which may drive up appetite in the long run. Additionally, low energy intake can contribute to a downregulation of metabolism (which is responsible for our energy utilization) as the body attempts to conserve energy. Furthermore, very low-calorie diets can also downregulate subconscious movements as a second attempt for energy conservation."

What this means is that the Cambridge diet can be unsustainable as low-calorie diets often lead to participants feeling hungry and restricted. "Naturally, when we feel restricted we're more prone to falling into a binge and restrict eating cycle, which in turn leads to overeating," Jenna explains.

And worryingly in the short-term, "low-calorie diets can contribute to symptoms such as fatigue, lethargy, dizziness and an inability to perform optimally due to a lack of energy."

Are there downsides to the Cambridge Diet?

Yes, plenty. "A low calorie diet is unlikely to work in the long-term due to the physiological changes such as increased hunger and downregulating the metabolism," says Jenna. "These changes can make it very challenging to stick to such a low-calorie intake."

"However, other key considerations for healthy weight loss include the mental and social aspects of a healthy diet. A very low-calorie diet may leave individuals experiencing low moods due to dietary restriction and a lack of energy and nutrients to support the production of the happy hormones," she says.

"Additionally, very low-calorie diets are less conducive to food-related social events and as a result, some people may begin to feel socially isolated if they have to miss out on events due to their diet."

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How much does the Cambridge Diet cost and how do you sign up?

Prices vary from consultant to consultant but, on average, dieters can expect to pay around £2.61 for a meal. 

Joining the plan is easy, you just need to sign up directly online (opens in new tab). You can search for a consultant near you, plus read testimonies from other people. 

Important rules to remember when following the Cambridge Diet

  • Keep drinking water—around 60% of your daily water consumption comes from the food you eat, so when consuming significantly less every day, you need to drink a great deal more H20 to compensate. The Cambridge Diet recommends sipping on at least 2.25 liters daily.
  • Get plenty of Zzz—going to bed early for a good quality night's sleep will really help, especially in the first few weeks. Also, if you're fully refreshed and can avoid becoming overtired, you will feel less hungry and are less likely to struggle with cravings. Struggling to nod off? Try a pair of these best earplugs for sleep or one of these best white noise machines.
  • Sip on tea—another way of getting enough water is to drink herbal and fruit teas. Camomile tea will help you drift off at night and peppermint tea could help combat some of the potential side effects of the diet such as constipation.
  • Eat your greens—stock up on delicious greens such as rocket, spinach, lettuce, watercress, cucumber, radishes or celery for step three onwards in the plan when a leafy salad makes a nutritious low-calorie lunch choice.
Grace Walsh
Health Editor

A digital health journalist with over five years experience writing and editing for UK publications, Grace has covered the world of health and wellbeing extensively for Cosmopolitan, The i Paper and more.

She started her career writing about the complexities of sex and relationships, before combining personal hobbies with professional and writing about fitness. Everything from the best protein powder to sleep technology, the latest health trend to nutrition essentials, Grace has a huge spectrum of interests in the wellness sphere. Having reported on the coronavirus pandemic since the very first swab, she now also counts public health among them.