The 1:1 Diet by Cambridge Weight Plan vs LighterLife

Jump to: At-a-glance comparison | Core approach differences | What is The 1:1 Diet? | What is LighterLife? | What is Second Nature? | Support and coaching | Pricing comparison | Clinical evidence | Who should choose each option | Frequently asked questions | Take home message

When comparing The 1:1 Diet by Cambridge Weight Plan, LighterLife, and Second Nature, the key difference lies in their approaches to weight loss and long-term weight maintenance.

The 1:1 Diet and LighterLife use very low-calorie diets (VLCDs) with meal-replacement products to promote rapid weight loss, typically providing 600-800 calories per day.¹

Second Nature takes a different approach, focusing on building sustainable habits through behavioural psychology, with options for both non-medication and medication-supported programmes.

At Second Nature, we’ve delivered NHS-commissioned weight-loss services since 2017, and our approach is backed by over 8 years of peer-reviewed clinical research.²

We offer both non-medication programmes (from £28/month) and medication-supported programmes with Mounjaro or Wegovy (from £149/month), giving you the flexibility to choose based on your needs and goals.

This guide compares the three programmes to help you decide which approach best aligns with your health goals, lifestyle, and preferences.

At-a-glance comparison

Core approach differences

The fundamental difference between these programmes lies in how they help you lose weight and, importantly, how they prepare you to maintain that weight loss.

Very low-calorie diets (VLCDs): The 1:1 Diet and LighterLife

Both The 1:1 Diet and LighterLife use meal replacement products as your sole or primary source of nutrition.

These products are nutritionally complete, providing essential vitamins and minerals while limiting daily calories to 600-800 on the strictest plans.

This approach typically leads to rapid weight loss, with many people losing a stone or more in the first month.

The body enters a state called ketosis, where it burns fat for fuel instead of carbohydrates, which can reduce hunger after the initial adjustment period.

VLCDs can be effective for people who need to lose weight quickly for medical reasons, such as before surgery, or who find the structure of complete meal replacement helpful.

However, very-low calorie diets have been shown to have a lasting impact on our metabolism.

Research on ‘The Biggest Loser’ participants – a TV show where participants had their calorie intake restricted by 70% – showed that 30 weeks after the start of the show, their metabolism had reduced by up to 500 calories per day.

This reduction in the amount of calories we burn each day during weight loss is called metabolic adaptation and can make maintaining weight loss in the long term very challenging.

The effect of metabolic adaptation due to very-low calorie intake is why Second Nature recommends losing weight as slowly as possible (around 0.5 – 1lbs per week).

Habit-based behaviour change: Second Nature

At Second Nature, we take a fundamentally different approach.

Rather than replacing meals with products, we help you build sustainable eating habits using real food from day one.

Our programme is built on behavioural psychology, helping you understand why you eat the way you do and developing practical strategies that fit your life.

We offer two pathways: a non-medication programme focused solely on habit change, and medication-supported programmes that combine Mounjaro or Wegovy with our behaviour change approach.

Research published in JMIR Formative Research shows that participants on our medication-supported programme lost an average of 19.1% of their starting weight at 12 months, with 77.7% achieving clinically significant weight loss of 10% or more.²

What is The 1:1 Diet by Cambridge Weight Plan?

The 1:1 Diet, formerly known as the Cambridge Diet, was developed in the 1980s by Dr Alan Howard at Cambridge University.

The programme uses nutritionally complete meal-replacement products, including shakes, soups, bars, and porridge, and combines them with weekly one-to-one support from a trained consultant.

How the 1:1 Diet works

The programme has six steps, ranging from 440 to 1,500 calories daily:

• Step 1 (Sole Source): 440-600 calories from 3-4 meal replacement products only
• Step 2: 600-800 calories with products plus a small conventional meal
• Steps 3-6: Gradually increasing calories and conventional food while reducing products

Consultants are typically former programme members who have completed training. They provide weekly weigh-ins, motivation, and product ordering.

The stepped approach helps you transition back to conventional eating, though this transition can be challenging without broader behaviour change support.

Pros and cons of The 1:1 Diet

Potential benefits:

• Structured approach with no meal planning required
• Rapid initial weight loss can be motivating
• Weekly accountability with your consultant
• Products are nutritionally complete

Potential drawbacks:

• Doesn’t teach you how to cook or eat real food
• Consultants aren’t registered nutrition professionals
• Social situations and eating out become difficult
• Risk of weight regain when returning to normal eating
• Side effects can include fatigue, headaches, and constipation
• Very little published evidence that these extreme approaches work in the long term

What is LighterLife?

LighterLife combines VLCD meal replacement products with cognitive behavioural therapy (CBT) and group support sessions.

Founded in 1996, the programme emphasises understanding the psychological aspects of eating alongside the nutritional intervention.

How LighterLife works

The TotalFast programme provides four Foodpacks daily, totalling 600-800 calories, as your sole source of nutrition.

What sets LighterLife apart from The 1:1 Diet is the inclusion of weekly group therapy sessions led by trained mentors.

These sessions use CBT and mindfulness techniques to help you understand your relationship with food and address emotional eating patterns.

Mentors are former members who have completed LighterLife’s training programme, though they aren’t qualified psychologists or therapists.

Pros and cons of LighterLife

Potential benefits:

• Addresses psychological aspects of eating through CBT
• Group support provides community and accountability
• Structured programme removes food decisions
• Rapid weight loss in the initial phases

Potential drawbacks:

• Higher cost than other VLCD programmes
• Mentors aren’t registered nutrition or psychology professionals
• Group format doesn’t suit everyone
• Still relies on meal replacements rather than real food
• Transition to normal eating can be challenging
• Very little published evidence that these extreme approaches work in the long term

What is Second Nature?

Second Nature is the UK’s most trusted weight-loss programme, having supported over 300,000 patients since 2017 through NHS-commissioned services.

Our approach is fundamentally different: we help you build sustainable habits using real food and behavioural psychology, with optional medication support.

How Second Nature works

We offer two main pathways:

Non-medication programme (from £28/month):

• Daily educational content on nutrition, psychology, sleep, and stress
• Support from UK-registered dietitians and nutritionists
• Custom app with food tracking, recipes, and progress monitoring
• Small peer support groups for community and accountability
• No calorie counting; focus on balanced, whole-food meals

Medication-supported programme (from £149/month):

• All non-medication programme features, plus
• Mounjaro or Wegovy prescription (subject to eligibility)
• Specialist support for managing medication and side effects
• Structured approach to building habits while appetite is reduced
• Post-medication transition planning

Why Second Nature is the UK’s most trusted programme

Our NHS partnership spanning over 8 years reflects the confidence healthcare professionals place in our approach.

We’ve published multiple peer-reviewed studies demonstrating our effectiveness:

• 19.1% average weight loss at 12 months on our medication programme²
• 77.7% of medication programme participants achieved ≥10% weight loss
• 5.9kg average weight loss at 12 weeks on our NHS programme⁴

Unlike VLCD programmes, all our health coaches are registered dietitians or nutritionists with nationally recognised qualifications.

Support and coaching comparison

The quality and type of support you receive significantly impact both your weight loss results and your ability to maintain them.

The 1:1 Diet support model

Consultants are former programme members who have completed The 1:1 Diet’s training.

You’ll have weekly one-to-one sessions for weigh-ins, motivation, and product ordering.

Consultants can encourage and share their personal experience, but they aren’t qualified to give detailed nutrition advice beyond the programme’s products.

LighterLife support model

Mentors lead weekly group sessions using CBT and mindfulness techniques.

Like the 1:1 Diet consultants, mentors are former members who have completed training rather than registered professionals.

The group format provides peer support and shared experiences, which many people find valuable.

Second Nature support model

All our health coaches are UK-registered dietitians or nutritionists, meaning they’ve completed accredited university degrees.

You’ll have access to your coach five days a week through both private and group chat.

Our coaches can answer detailed nutrition questions, help you navigate social situations, and provide personalised advice based on your health conditions and goals.

This level of professional support would typically cost £40-100 per hour in private practice.

Pricing comparison

Understanding the full cost helps you make an informed decision based on your budget and needs.

The 1:1 Diet pricing

• Approximately £2.99 per product
• ~£62.79 per week (3 products daily plus consultation)
• ~£272 per month on Step 1
• Costs decrease as you progress to higher steps with fewer products

Pricing varies between consultants, so it’s worth confirming exact costs before starting.

LighterLife pricing

• TotalFast subscription: from £79 per week
• ~£343 per month
• Includes Foodpacks and access to mentor support
• Group sessions included at no extra cost

Second Nature pricing

Non-medication programme:

• 14-day trial: £9.99
• Monthly subscription: £28-£38
• Includes app access, health coach support, and peer groups

Medication-supported programme:

• First month: from £149
• Subsequent months: £149-£349 depending on the dose
• Includes medication, delivery, app access, and professional support

What’s included in the price

Clinical evidence and outcomes

When choosing a weight-loss programme, it’s important to understand what evidence supports each approach.

VLCD research

Very low-calorie diets have been studied extensively and can produce significant short-term weight loss.

Research shows VLCDs typically result in 1.5-2.5kg of weight loss per week during the initial phase.⁵

However, long-term maintenance is challenging. Studies suggest that without ongoing support and behaviour change, much of the weight lost on VLCDs is regained within 1-2 years.⁶

Neither The 1:1 Diet nor LighterLife have published programme-specific long-term outcomes in peer-reviewed journals, though LighterLife has published one cost-effectiveness analysis.³

Second Nature’s published research

Multiple peer-reviewed publications support our approach:

12-month semaglutide outcomes (JMIR Formative Research, 2025):²

• 19.1% average weight loss for active participants
• 77.7% achieved ≥10% weight loss
• 61.5% achieved ≥15% weight loss
• Side effects decreased over time, with 69% reporting none by month 12

NHS programme outcomes (British Medical Journal, 2022):⁴

• 5.9kg average weight loss at 12 weeks
• 62.5% achieved at least 5% weight loss by 3 months
• 40% of type 2 diabetes patients reduced HbA1c below diagnostic thresholds

These outcomes demonstrate that our habit-based approach, with or without medication, delivers sustainable results supported by rigorous research.

Who should choose each programme?

Each approach has its place, and the right choice depends on your individual circumstances, preferences, and goals.

Consider The 1:1 Diet if:

• You prefer one-to-one support over group settings
• You want the structure of a complete meal replacement
• You’re comfortable with a consultant who isn’t a registered professional
• You need to lose weight quickly for a specific reason
• You have a clear plan for transitioning back to normal eating

Consider LighterLife if:

• You value the psychological component and the CBT approach
• You thrive in group support settings
• You want to understand your emotional relationship with food
• You’re comfortable with the higher price point
• You prefer complete meal replacement for simplicity

Consider Second Nature if:

• You want to learn sustainable habits using real food
• You value support from registered nutrition professionals
• You’re interested in medication-supported weight loss (Mounjaro or Wegovy)
• You want a programme backed by an NHS partnership and peer-reviewed research
• You’re focused on long-term weight maintenance, not just initial loss
• You prefer a flexible approach that fits around your life
• You want the peace of mind that comes with clinical evidence

Frequently asked questions

Which programme produces the fastest weight loss?

VLCDs such as The 1:1 Diet and LighterLife typically result in faster initial weight loss (1.5-2.5kg per week) due to severe calorie restriction.

However, research shows that rapid weight loss is often followed by regain, and long-term outcomes depend more on sustainable habit change than initial speed.

Are VLCDs safe?

VLCDs are generally safe for most adults when followed correctly and with appropriate monitoring, but they’re not suitable for everyone.

They should be avoided during pregnancy, breastfeeding, or if you have certain medical conditions.

Still, the lasting effects of very-low calorie diets on our metabolism suggest that they might make it harder to maintain a healthy BMI in the long term.

When we restrict our calorie intake to such a low level, our body responds by reducing the amount of calories we burn each day; we call this metabolic adaptation.

Research on participants on very low calorie diets has shown that this lower metabolism can last in the long term, even when you’ve reached your weight loss goal.

Having a lower metabolism would restrict the number of calories you’d be able to eat each day, so maintaining a lower weight becomes harder, particularly as you age.

Always consult your GP before starting a VLCD.

Can I get Mounjaro or Wegovy with The 1:1 Diet or LighterLife?

No, neither The 1:1 Diet nor LighterLife offer weight-loss medications.

Second Nature is the only programme among these three that offers medication-supported options alongside behaviour change support.

What happens when I stop taking meal replacement products?

This is one of the biggest challenges with VLCD programmes.

Without learning to cook and eat real food, many people struggle when transitioning back to normal eating.

Both programmes have stepped approaches to reintroduce food, but the transition can be difficult without broader behaviour change support.

Why is Second Nature’s non-medication programme so much cheaper?

Our non-medication programme doesn’t include the cost of meal replacement products or medication.

Instead, you eat real food (which you’d buy anyway) while accessing our app, health coach support, and educational content.

Does Second Nature work without medication?

Yes, our non-medication programme is effective for many people.

Our NHS trial showed 5.9kg average weight loss at 12 weeks without medication.⁴

However, for people with more significant weight to lose or those who’ve struggled with other approaches, medication can provide additional support.

How do I know which approach is right for me?

Consider your goals, budget, and what’s worked (or hasn’t) in the past.

If you’ve tried VLCDs before and regained weight, a habit-based approach might be more sustainable.

If you have significant weight to lose and want clinical support, our medication programme offers NHS-trusted care.

Are the consultants and mentors qualified nutritionists?

No. Both The 1:1 Diet consultants and LighterLife mentors are former programme members who’ve completed internal training.

They aren’t registered with professional bodies like the Health and Care Professions Council or Association for Nutrition.

Second Nature’s health coaches are all UK-registered dietitians or nutritionists with nationally recognised qualifications.

Take home message

The 1:1 Diet, LighterLife, and Second Nature offer fundamentally different approaches to weight loss.

VLCDs can produce rapid results, but the challenge lies in maintaining that weight loss when you return to normal eating.

The psychological support offered by LighterLife’s CBT approach is valuable, but the combination of meal replacement products and non-professional mentors has limitations.

References

1. National Institute for Health and Care Excellence. (2014). Obesity: identification, assessment and management (CG189)
2. Richards, R., et al. (2025). A Remotely Delivered, Semaglutide-Supported Weight Management Program: 12-Month Outcomes. JMIR Formative Research, 9(1), e72577.
3. Counterweight Project Team. (2014). The cost-effectiveness of the LighterLife weight management programme. Clinical Obesity, 4(3), 180-188.
4. Richards, R., et al. (2022). The Potential of a Digital Weight Management Program to Support Specialist Weight Management Services. JMIR Diabetes, 7(2), e35156.
5. Astbury, N.M., et al. (2018). Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET). BMJ, 362, k3760.
6. Sumithran, P., & Proietto, J. (2013). The defence of body weight: a physiological basis for weight regain after weight loss. Clinical Science, 124(4), 231-241.