What are the Cambridge diet steps? A Complete Guide to the 1:1 Diet Program

October 23, 2025 •

4 min read

Originally developed in the 1960s at Cambridge University for very low-calorie diets, the Cambridge Diet has since been rebranded as the 1:1 Diet and is structured around a multi-step program for weight loss. A personalized consultant guides participants through these key phases, starting with a very low-calorie approach using specialized meal replacement products.

Quick Summary

The Cambridge Diet, now called the 1:1 Diet, features six structured steps that gradually increase calorie intake. Beginning with meal replacements and very low calories, the program slowly reintroduces conventional foods until a maintenance phase is reached, all with one-on-one consultant support.

Key Points

Six Progressive Steps: The Cambridge Diet follows a plan of six distinct steps, with calorie intake increasing and conventional food being reintroduced gradually over time.
Meal Replacements at the Core: The initial phases heavily rely on specialized meal replacement products like shakes and soups to achieve a very low-calorie intake.
Personal Consultant Support: Dieters work one-on-one with a consultant who provides guidance and tracks progress throughout the program.
Transition to Regular Food: Later steps focus on transitioning from meal replacements to healthy, conventional meals to develop sustainable eating habits.
Rapid Initial Weight Loss: The initial restrictive phase is designed to induce rapid weight loss by putting the body into a state of ketosis.
Risks and Sustainability: Concerns exist regarding the long-term sustainability, potential side effects, and risk of weight regain associated with very low-calorie diets.

What is the Cambridge Diet?

Developed in the 1960s by researchers at the University of Cambridge, the diet was created as a very low-calorie diet (VLCD) for individuals with obesity. Today, it is known as The 1:1 Diet by Cambridge Weight Plan, emphasizing the one-to-one support provided by a consultant throughout the process. This multi-step program is centered around weight-loss using proprietary meal replacement products such as shakes, soups, and bars, with the gradual reintroduction of regular foods over time.

The Role of a Consultant

A key aspect of the 1:1 Diet is the weekly check-in with a trained consultant. This consultant helps tailor the program to individual needs, monitors progress, and provides support and motivation. While some consultants may be trained to provide nutritional guidance, they are not always qualified medical professionals, which is an important consideration for a restrictive program.

The Six Steps of the Cambridge Diet

The 1:1 Diet is divided into six steps, or phases, that a dieter progresses through. The starting step is determined by the consultant based on the dieter's weight-loss goals and needs, and some steps can be skipped.

Step 1: Sole Source

This is the most restrictive phase and can last up to 12 weeks. It involves consuming only 3-4 Cambridge meal replacement products daily, totaling 415–600 calories, and drinking at least 2.25 liters of water. The goal is rapid weight loss through a very low-calorie intake.

Step 2: Sole Source Plus

Step 2 introduces some conventional food. Dieters consume 2 Cambridge meal replacement products, along with a protein-rich meal of about 200 calories and some vegetables, for a total of approximately 810 calories per day.

Step 3: Mix and Match

Lasting two weeks, this phase increases daily intake to approximately 1,000 calories. It includes 2 Cambridge products, a low-calorie breakfast, and a salad for both lunch and dinner.

Step 4: Higher Calorie

This two-week step provides about 1,200 calories daily. The plan incorporates 2 Cambridge products, breakfast, lunch, and dinner, plus an optional snack, further aiding the transition to conventional eating.

Step 5: Full Meals

Also lasting two weeks, Step 5 increases the calorie intake to around 1,500 per day. It includes one Cambridge product, breakfast, lunch, and dinner, along with a snack, focusing on portion control and healthy cooking.

Step 6: Maintenance

The final stage is ongoing and aims for long-term weight management. Dieters eat a healthy, regular diet with the option to use Cambridge products for support.

Comparison: Starting vs. Maintenance Phase


Feature	Step 1: Sole Source (Initial)	Step 6: Maintenance (Long-term)
Caloric Intake	~415–600 calories per day	~1,200+ calories per day
Food Source	Exclusively Cambridge meal replacements	Healthy, regular meals with optional products
Carbohydrates	Very limited, puts body into ketosis	Normal, balanced carbohydrate intake
Consultant Support	Regular weekly check-ins for support	Available for ongoing support as needed
Duration	Up to 12 weeks	Indefinite

Pros and Cons of the Cambridge Diet

Pros:

Rapid Weight Loss: The very low-calorie intake in the initial steps can lead to significant and fast weight loss.
Structured Plan: The prescribed steps eliminate the guesswork of meal planning, which is beneficial for those who struggle with portion control.
Nutritionally Complete: The meal replacement products are fortified to ensure they provide essential vitamins and minerals, even with low-calorie consumption.
Break Unhealthy Habits: The initial reliance on meal replacements can help break cycles of unhealthy eating.

Cons:

Restrictive and Unsustainable: The diet is highly restrictive and heavily reliant on processed meal replacement products, making it potentially unsustainable long-term and possibly leading to a poor relationship with food.
Side Effects: The severe calorie restriction can cause unpleasant side effects such as headaches, constipation, fatigue, and dizziness.
High Cost: The cost of the meal replacement products can be a significant financial burden.
Risk of Weight Regain: Many nutritionists warn that rapid weight loss through extreme calorie restriction can lead to a slowed metabolism and a high risk of regaining the lost weight after the diet is over.

Conclusion

The Cambridge Diet, now known as the 1:1 Diet, offers a structured, multi-step approach to weight loss using meal replacements and consultant support. The program starts with a very low-calorie phase and gradually reintroduces conventional foods, with the final step focusing on long-term weight maintenance. While it can deliver rapid initial results, the high cost, restrictive nature, and potential side effects make it unsuitable for everyone. Experts recommend that very low-calorie diets should be undertaken under medical supervision due to the health risks. A sustainable approach to weight loss usually involves a balanced diet, exercise, and permanent healthy lifestyle changes rather than relying solely on meal replacements.

For more information on the official 1:1 Diet plan and products, you can visit their website.

This article is for informational purposes only and does not constitute medical advice. Consult with a healthcare professional before starting any weight-loss program.

Frequently Asked Questions

The Cambridge Diet has been rebranded and is now officially known as The 1:1 Diet by Cambridge Weight Plan.

The Cambridge Diet, or 1:1 Diet, is typically divided into six steps that vary in calorie level and meal composition, from initial meal replacement to long-term maintenance.

The initial and most restrictive step is 'Sole Source,' where dieters consume only 3-4 Cambridge meal replacement products daily for up to 12 weeks, with a calorie intake between 415-600 kcal.

Yes, while the initial steps consist solely or primarily of meal replacements, later steps gradually reintroduce healthy, conventional meals, like breakfast, lunch, and dinner.

Due to the very low-calorie intake, common side effects can include headaches, constipation, fatigue, dizziness, and bad breath, especially in the early stages.

Some experts question the long-term sustainability of the Cambridge Diet, citing concerns that the restrictive nature and lack of habit-building can lead to weight regain.

Yes, the 1:1 Diet model includes mandatory, one-on-one support from a trained consultant who guides dieters through the program and sells them the necessary products.