What Foods Are Allowed on the 1 1 1 Diet?

October 26, 2025 •

3 min read

The 1:1 Diet, originally developed in the 1960s, is a medically-researched weight management plan that uses specific products to control calorie intake. The question of what foods are allowed on the 1 1 1 diet depends entirely on which of the plan's six steps you are following, as it involves a very specific, phased approach.

Quick Summary

This guide explains the food allowances for each of the six steps of The 1:1 Diet. It details the reliance on proprietary meal replacements in the initial stages and the gradual reintroduction of regular, healthy foods in later phases.

Key Points

Product-Based Start: The 1:1 Diet begins with exclusive use of proprietary meal replacement products like shakes, soups, and bars to trigger rapid weight loss.
Phased Reintroduction: The plan gradually reintroduces regular, healthy foods in controlled portions as you move through its six steps.
Nutritionally Complete: All meal replacement products are formulated to provide the body with its essential daily vitamins, minerals, and nutrients.
Consultant-Guided: A personal consultant provides one-to-one support and guidance on food choices for each specific step.
Maintenance Phase: The final stages focus on incorporating sustainable, balanced eating habits with real foods to maintain weight loss.
Not a Macro Ratio: The 1:1 Diet is a brand-specific meal replacement program, distinct from the 'one protein, one carb, one fat' interpretation.

What is The 1:1 Diet?

The 1:1 Diet, formerly known as the Cambridge Weight Plan, is a structured weight loss program that combines proprietary meal replacement products with one-to-one support from a consultant. It operates on a six-step system, where the calorie level and allowed food types change as you progress toward your target weight and then into maintenance. The initial, more restrictive steps focus on achieving rapid weight loss through a very-low-calorie diet (VLCD), while later stages teach sustainable, long-term eating habits.

Foods Allowed in the Initial Steps (Total Diet Replacement)

During the first and most intensive steps of the 1:1 Diet, dieters exclusively consume the brand's low-calorie, nutritionally-complete products. This phase is designed to put the body into ketosis, where it burns stored fat for energy due to a lack of carbohydrates.

List of Allowed Products in Initial Steps:

Shakes: Available in a variety of flavors like chocolate, vanilla, and cappuccino.
Soups: Options include vegetable, chicken & mushroom, and oriental chilli flavors.
Porridge: Flavors often include original, apple & cinnamon, and mixed berry.
Bars and Bites: Products like chocolate chewy bars, fruit & nut bars, and salted caramel bites are available.
Savoury Meals: Microwavable dishes such as spaghetti bolognese and green pesto pasta are options for some steps.
Smoothies: Fruity smoothies like strawberry & banana are part of the product line.

In addition to the specific products, dieters must consume at least 2.25 liters of water per day. Some plans also allow herbal teas, black coffee, and water flavorings. Alcoholic beverages are prohibited due to their high-calorie content and minimal nutritional value.

Foods Allowed in Transition and Maintenance Steps

As dieters move through the six steps, the plan gradually reintroduces regular, everyday food alongside the meal replacement products. This phase is crucial for learning portion control and developing healthy eating patterns for long-term success. Your consultant will guide you on the specific number of products and regular meals for your current step.

Examples of Regular Foods Allowed in Later Steps:

Lean Protein: Grilled chicken breast, fish (like tuna or salmon), and eggs.
Vegetables: Leafy greens (spinach, kale), broccoli, carrots, bell peppers, and other mixed vegetables.
Whole Grains and Carbs: Brown rice, whole wheat bread, and oatmeal.
Dairy and Alternatives: Low-fat yogurt, milk, and certain dairy alternatives.
Healthy Fats: Olive oil, nuts, and avocados, used in moderation.

Comparing the Initial vs. Maintenance Phases


Feature	Initial (VLCD) Phases	Maintenance Phases
Food Source	Exclusive use of 1:1 Diet products.	Combination of 1:1 Diet products and conventional meals.
Calorie Level	Very low, typically 440-800 calories per day.	Higher calorie intake, personalized for stable weight.
Carb Intake	Very low, pushing the body into ketosis.	Gradual reintroduction of healthy carbohydrates.
Goal	Rapid initial weight loss.	Sustainable weight management and healthy eating habits.
Flexibility	Highly structured and restrictive.	More flexible, teaching long-term dietary control.

Addressing the Alternative “1:1:1” Concept

It is important to differentiate The 1:1 Diet from the more general nutritional guideline of a “1:1:1 diet,” which suggests balancing one protein, one carbohydrate, and one fat source at each meal. While The 1:1 Diet's maintenance phases incorporate these principles, the initial VLCD steps are not structured this way. The specific meal replacement products are formulated to provide balanced nutrition within a very low-calorie framework, not a simple 1:1:1 macro ratio.

Conclusion

The foods allowed on the 1 1 1 diet, or more accurately The 1:1 Diet by Cambridge Weight Plan, are highly specific and depend on the phase of the program. The journey starts with nutritionally-complete, brand-specific meal replacement products to achieve rapid weight loss. As you progress, your consultant helps you transition to include a controlled range of healthy, everyday foods to build sustainable habits. Adhering to the specific step you are on is critical for both the diet's effectiveness and your overall safety, as very low-calorie diets require careful management. For specific guidance on which products and foods are right for you, and to learn more about the products, it is best to speak directly with an accredited consultant.

For more information on the official products, visit the one2onediet.com website.

Frequently Asked Questions

No, the initial, very low-calorie steps of the 1:1 Diet involve replacing all regular food with the brand's proprietary products to initiate rapid weight loss.

The product range includes a wide variety of shakes, soups, porridge, pasta dishes, bars, and smoothies.

The diet follows a six-step system, gradually increasing the number of conventional, low-calorie meals and reducing the reliance on meal replacement products over time.

The 1:1 Diet offers a range of vegetarian and some lactose-free products. You should consult with a 1:1 Diet Consultant for specific guidance on suitable products.

Yes, as you progress through the later steps, your consultant will provide a list of suitable foods and recipes to incorporate alongside the meal replacement products.

No, the '1:1:1' concept of balancing macros is a different dietary approach. The 1:1 Diet by Cambridge Weight Plan is a brand-specific meal replacement plan with one-to-one support.

Yes, plenty of water (at least 2.25 liters) is essential. Some plans also allow herbal teas, black coffee, and specific water flavorings.

For the initial total diet replacement phases, only gentle walking is recommended. More rigorous exercise is introduced in later steps with higher calorie intake.