Direct Answer: A very low calorie diet (VLCD) is a short-term, medically supervised eating plan that typically provides 800 calories or less per day. Research suggests that VLCDs may help some people with type 2 diabetes achieve significant improvements in blood sugar control, though this approach is not appropriate for everyone and requires close medical oversight. If you're curious about whether a VLCD might be right for you, this article explains what the research shows, who may be a candidate, and why medical supervision is essential.
Key Takeaways
- VLCDs are not a DIY approach. They should only be undertaken with medical supervision, especially if you take diabetes medications.
- Short-term, not long-term. VLCDs are typically used for 8–12 weeks, followed by a structured transition to sustainable eating.
- Medication adjustment is critical. Glucose-lowering medications may need adjustment to prevent dangerous low blood sugar (hypoglycemia).
- Not appropriate for everyone. Certain health conditions and life circumstances make VLCDs unsuitable or risky.
- Maintenance matters most. The real challenge is sustaining improvements after the VLCD phase through lasting lifestyle habits.
Table of Contents
- What Is a Very Low Calorie Diet?
- How VLCDs May Improve Blood Sugar
- What the Research Shows
- Safety Considerations and Risks
- What Medical Supervision Looks Like
- Transitioning Off a VLCD
- Your 2-Week Transition Template
- Checklist: Questions to Ask Your Doctor
- Frequently Asked Questions
What Is a Very Low Calorie Diet?
A very low calorie diet (VLCD) is an intensive, short-term eating plan that typically provides 800 calories or fewer per day. To put this in perspective, most adults need 1,600–2,400 calories daily to maintain their weight. A VLCD represents a significant reduction.
VLCDs may use:
- Meal replacement formulas (shakes, bars, or soups) that are nutritionally complete
- Real food plans carefully designed to meet protein and micronutrient needs within the calorie limit
- Combination approaches that include both meal replacements and some whole foods
The key distinction from simply "eating less" is that VLCDs are designed to be nutritionally adequate despite the low calorie count. This requires careful planning—which is why medical supervision is essential.
VLCD vs. Other Approaches
| Approach | Typical Calories | Duration | Supervision Needed? |
|---|---|---|---|
| Very Low Calorie Diet (VLCD) | 400–800/day | 8–12 weeks | Yes, required |
| Low Calorie Diet (LCD) | 1,000–1,500/day | Ongoing | Recommended |
| Low-Carb Diet | Varies | Ongoing | Helpful |
| Standard Healthy Eating | 1,600–2,400/day | Ongoing | Optional |
How VLCDs May Improve Blood Sugar
Research suggests several mechanisms through which VLCDs may benefit people with type 2 diabetes:
Energy Deficit and Fat Loss
When you consume significantly fewer calories than your body uses, it turns to stored energy. This leads to fat loss—including fat stored in and around organs.
Reduced Liver and Pancreatic Fat
Studies have found that excess fat in the liver and pancreas may contribute to insulin resistance and impaired insulin production. VLCDs have been shown to reduce fat in these organs, which may help improve their function.
The DiRECT trial, a landmark study published in The Lancet, found that participants who lost substantial weight through a low-calorie program showed significant reductions in liver and pancreatic fat.
Improved Insulin Sensitivity
As stored fat decreases, cells may become more responsive to insulin. This improved "insulin sensitivity" means your body can manage blood sugar more effectively with less insulin.
Important Caveats
These improvements are not guaranteed and depend on many individual factors. Some people respond better than others, and maintaining improvements requires ongoing lifestyle changes after the VLCD phase ends.
What the Research Shows
Several major studies have examined VLCDs in people with type 2 diabetes:
The DiRECT Trial
The Diabetes Remission Clinical Trial (DiRECT) followed participants through a structured weight management program that began with a low-calorie phase.
Key findings at 12 months:
- 46% of participants achieved diabetes remission (defined as HbA1c below 6.5% without medication)
- Remission rates were strongly linked to weight loss amount
- Participants who maintained weight loss were more likely to sustain remission
The LOOK AHEAD Trial
The LOOK AHEAD study examined intensive lifestyle intervention (including calorie restriction) in people with type 2 diabetes over many years.
Findings showed that participants who achieved greater weight loss experienced more improvements in blood sugar control, though the study also highlighted the challenge of maintaining weight loss long-term.
What These Studies Tell Us
The research consistently shows that significant calorie restriction can produce meaningful short-term improvements in metabolic markers. However, the studies also emphasize that:
- Individual responses vary widely
- Maintenance is the biggest challenge
- Medical supervision is important for safety
- Long-term success depends on sustainable lifestyle habits
Safety Considerations and Risks
VLCDs are not without risks. Understanding these is essential before considering this approach.
Who Should NOT Follow a VLCD
VLCDs are generally not appropriate for:
- Pregnant or breastfeeding women
- People with a history of eating disorders
- Those with certain heart conditions or recent cardiac events
- People with severe kidney or liver disease
- Those taking certain medications that cannot be adjusted
- Children and adolescents
This list is not exhaustive. Your healthcare provider can help determine if you have any conditions that would make a VLCD inadvisable.
Potential Side Effects
Common side effects during VLCDs may include:
- Fatigue and low energy, especially in the first few days
- Headaches as your body adjusts
- Constipation due to reduced food volume
- Dizziness, particularly when standing quickly
- Cold intolerance
- Dry skin or hair changes
Most side effects are temporary and manageable with proper supervision.
Serious Risks
More serious concerns include:
- Hypoglycemia (low blood sugar): This is a significant risk for people taking insulin or certain oral diabetes medications. Medications typically need to be reduced or stopped during a VLCD to prevent dangerous low blood sugar episodes.
- Gallstones: Rapid weight loss increases the risk of developing gallstones.
- Nutrient deficiencies: Without careful planning, VLCDs can lead to inadequate intake of essential vitamins, minerals, and protein.
- Electrolyte imbalances: These can affect heart rhythm and muscle function.
- Muscle loss: Without adequate protein and, ideally, some resistance exercise, you may lose muscle mass along with fat.
These risks underscore why medical supervision is non-negotiable.
What Medical Supervision Looks Like
A properly supervised VLCD program typically includes several components:
Initial Assessment
Before starting, your healthcare team should:
- Review your complete medical history
- Conduct a physical examination
- Order baseline blood tests (blood sugar, kidney and liver function, electrolytes, lipids)
- Review all medications and create an adjustment plan
- Assess for conditions that would make a VLCD inadvisable
- Discuss realistic expectations and commitment
During the VLCD Phase
Ongoing supervision typically includes:
- Regular check-ins (weekly or biweekly) with a healthcare provider
- Medication monitoring and adjustment as weight loss progresses
- Blood tests to monitor kidney function, electrolytes, and other markers
- Nutritional counseling to ensure the diet meets protein and micronutrient needs
- Side effect management
- Psychological support for the challenges of significant dietary restriction
The VLCD Itself
A medically supervised VLCD typically includes:
- Adequate protein (at least 50–70 grams daily) to preserve muscle mass
- Essential vitamins and minerals through supplements or fortified products
- Adequate hydration (typically 2+ liters of non-caloric fluids daily)
- Meal replacements that are specifically designed for VLCDs, OR
- Real food plans carefully designed by a registered dietitian
Transition Planning
A responsible VLCD program includes a plan for transitioning back to regular eating—this is addressed in the next section.
Transitioning Off a VLCD
The transition phase is arguably the most important part of a VLCD program. Without a structured transition, rapid weight regain is common.
Why Transition Matters
During a VLCD, your body adapts to lower calorie intake. Jumping straight back to normal eating can lead to:
- Rapid weight regain as the body "overshoots"
- Blood sugar spikes as higher-calorie foods return
- Digestive discomfort from suddenly larger food volumes
- Psychological challenges and feelings of failure
Principles of Successful Transition
A good transition focuses on:
- Gradual calorie increase (typically 100–200 calories per week)
- Introducing whole foods one food group at a time
- Prioritizing protein at each meal
- Maintaining structure with planned meals and timing
- Building sustainable habits that will support long-term maintenance
- Continued monitoring of blood sugar and weight
Your 2-Week Transition Template
This is a general framework. Your healthcare team should customize it to your situation.
Week 1: Building the Foundation (Target: 1,000–1,200 calories)
Day 1-3:
- Continue with 2 meal replacements
- Add 1 small meal: lean protein (3-4 oz) + non-starchy vegetables
- Focus on drinking adequate water
Day 4-7:
- Continue with 1-2 meal replacements
- Add 2 small meals with protein + vegetables
- Introduce a small serving of complex carbohydrates (½ cup whole grains or legumes) at one meal
Week 2: Expanding Variety (Target: 1,200–1,400 calories)
Day 8-10:
- Reduce to 1 meal replacement (if still using)
- Eat 2-3 small, structured meals
- Add a serving of fruit or additional complex carbohydrates
- Include healthy fats (small portions of nuts, olive oil, avocado)
Day 11-14:
- Transition to all whole-food meals if comfortable
- Continue structured eating patterns
- Maintain protein-first approach at each meal
- Practice portion awareness
Ongoing Maintenance Principles
After the 2-week transition:
- Continue structured eating with planned meals
- Keep protein as a priority at every meal
- Limit ultra-processed foods and added sugars
- Build in regular physical activity
- Monitor your weight weekly
- Stay connected with your healthcare team
- Develop strategies for managing challenging situations (travel, social events, stress)
For more on building lasting habits, see our article on Building Sustainable Health Habits That Last.
Checklist: Questions to Ask Your Doctor
If you're considering a VLCD, use this checklist to guide your conversation with your healthcare provider. Copy or print this list to bring to your appointment.
Before Starting:
- Am I a good candidate for a VLCD given my health history?
- Are there any conditions I have that would make this approach risky?
- How will my diabetes medications need to be adjusted?
- What monitoring will you provide during the program?
- How often will we check in?
- What blood tests will you order, and how frequently?
- Should I work with a registered dietitian during this process?
About the Program:
- Do you recommend meal replacements or a real-food approach?
- How long should the VLCD phase last?
- What protein intake do you recommend?
- What supplements will I need?
- What side effects should I watch for?
- When should I contact you urgently?
About Transition and Maintenance:
- What does the transition phase look like?
- How quickly should I add calories back?
- What support is available for long-term maintenance?
- What are realistic expectations for maintaining results?
General:
- Is there a program you recommend, or will this be managed through your office?
- What are the costs, and is any portion covered by insurance?
- What resources can you point me to for more information?
Frequently Asked Questions
Is a VLCD safe for type 2 diabetes?
A VLCD may be safe for some people with type 2 diabetes when done under close medical supervision. The key concern is the risk of hypoglycemia (low blood sugar) if diabetes medications are not properly adjusted. This is why medical oversight is essential—your healthcare provider can monitor your blood sugar and adjust medications to keep you safe.
What's the difference between a VLCD and a low-carb diet?
A VLCD focuses on total calorie restriction (typically 800 or fewer calories), while a low-carb diet restricts carbohydrates but may allow higher overall calories. Both approaches may improve blood sugar control, but they work differently. VLCDs are short-term interventions, while low-carb diets can often be sustained long-term. Discuss with your healthcare provider which approach might be appropriate for your situation.
How much weight can you lose on a VLCD?
Weight loss varies by individual, but typical losses during an 8–12 week VLCD range from 30–50 pounds. However, rapid weight loss isn't the only goal—what matters more is whether improvements in metabolic health can be maintained long-term through sustainable lifestyle changes.
Will I regain the weight after stopping the VLCD?
Regain is common if the VLCD phase isn't followed by a structured transition and ongoing lifestyle changes. Research shows that people who develop sustainable eating and activity habits, maintain regular check-ins with healthcare providers, and address the behavioral aspects of eating are more likely to maintain their results.
Can I exercise during a VLCD?
Light to moderate activity (like walking) is typically encouraged, but intense exercise may be limited during the VLCD phase due to the low calorie intake. Your healthcare provider can advise on appropriate activity levels based on your individual situation and how you're feeling.
How do I know if I need my medications adjusted?
This should be determined by your healthcare provider before and during the VLCD. Generally, insulin and sulfonylureas (a class of diabetes medication) often need to be reduced or stopped to prevent low blood sugar. Never adjust your medications on your own—this can be dangerous.
Is a VLCD the same as fasting?
No. While both involve significant calorie restriction, a properly designed VLCD provides essential nutrients (protein, vitamins, minerals) to minimize health risks and preserve muscle mass. Extended fasting without nutritional support carries different and often greater risks.
What happens if I can't complete the full VLCD program?
This isn't a failure. Discuss with your healthcare team—there may be options to modify the program or transition to a different approach that's more sustainable for you. The goal is long-term health improvement, and there are multiple paths to get there.
Considering Your Next Steps
If you're interested in learning more about structured approaches to metabolic health improvement, the Done With Diabetes program offers a lifestyle-first approach that emphasizes sustainable habits over extreme interventions.
For personalized guidance, Start Program to explore the Vynleads app tools for tracking, coaching, and community support.
Important: Always discuss significant dietary changes with your healthcare provider, especially if you take medications for diabetes or other conditions. This article is for educational purposes and does not constitute medical advice.
References
- Lean, M.E., et al. "Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial." The Lancet 391.10120 (2018): 541-551.
- National Institute of Diabetes and Digestive and Kidney Diseases. Look AHEAD Trial. Accessed January 2026.
- American Diabetes Association. Standards of Medical Care in Diabetes. Diabetes Care 2024.
- National Health Service (UK). Very Low Calorie Diets. Accessed January 2026.
- Taylor, R. "Calorie restriction and reversal of type 2 diabetes." Expert Review of Endocrinology & Metabolism 11.6 (2016): 521-528.
This information is for educational purposes only. It is not medical advice. VLCDs should only be undertaken with medical supervision. Please consult your healthcare provider before making changes to your diet or medications.
Last reviewed: January 2026