What is a Very Low-Calorie Diet?
An 800 calorie diet is classified as a Very Low-Calorie Diet (VLCD) because it provides significantly fewer calories than the average daily intake needed for maintenance. In recent years, this dietary approach was popularized by Dr. Michael Mosley's 'Fast 800' program, which often combines the daily calorie restriction with intermittent fasting and a Mediterranean-style eating pattern. It is important to distinguish this structured, medically-inspired approach from uncontrolled, fad dieting.
How the 800-Calorie Diet Works
This diet works by creating a substantial calorie deficit, forcing the body to use its energy reserves, including stored fat, for fuel. For some, this process can lead to mild ketosis, a metabolic state where the body primarily burns fat for energy after its initial glucose stores are depleted. Additionally, the very low carbohydrate intake in many 800-calorie plans can help improve insulin resistance, particularly for individuals with pre-diabetes or type 2 diabetes. The regimen is typically followed for a short period, often 8 to 12 weeks, and should be followed by a more sustainable eating plan to maintain weight loss.
Potential Benefits
For those who are clinically obese and under strict medical supervision, an 800 calorie diet can offer several key benefits:
- Rapid Weight Loss: The most significant draw is the swift and substantial weight reduction it can produce. This quick progress can be highly motivating for individuals with a large amount of weight to lose.
- Improved Metabolic Health: Studies have shown improvements in blood sugar levels, blood pressure, and cholesterol, particularly in individuals with type 2 diabetes. Some research, like the DiRECT trial, even suggests the possibility of achieving diabetes remission.
- Targeting Visceral Fat: The diet is designed to help reduce visceral abdominal fat, which is the harmful fat stored around internal organs and is linked to increased risk of chronic diseases.
- Metabolic Reset: By shifting the body's primary fuel source from glucose to fat, proponents claim it can help reset metabolic function.
Associated Risks and Side Effects
Despite its potential benefits under the right circumstances, an 800-calorie diet is not without significant risks and is not for everyone.
- Nutrient Deficiencies: Severe calorie restriction makes it extremely difficult to get all the necessary vitamins, minerals, and other essential nutrients, leading to deficiencies over time.
- Muscle Loss: Rapid weight loss on a VLCD can lead to a loss of lean muscle mass along with fat. This can be counterproductive as muscle mass helps maintain a higher metabolic rate.
- Metabolic Slowdown: In an attempt to conserve energy, the body may slow down its metabolism. This can make it harder to keep the weight off after the diet ends and increases the likelihood of regaining it.
- Gallstone Formation: Rapid weight loss is a known risk factor for developing gallstones.
- Common Side Effects: Many people experience mild side effects like fatigue, headaches, dizziness, constipation, and nausea, especially during the initial phase.
- Psychological Impact: The restrictive nature of the diet can increase feelings of hunger, irritability, and may contribute to an unhealthy relationship with food, particularly for those with a history of disordered eating.
An Example 800-Calorie Meal Plan
Following a structured, nutrient-dense plan is crucial for those attempting an 800-calorie diet. Here is a sample day inspired by the Mediterranean approach:
- Breakfast (approx. 200 calories): Two scrambled eggs with a handful of spinach and mushrooms cooked with a teaspoon of olive oil.
- Lunch (approx. 250 calories): A large, mixed green salad with grilled chicken breast, cucumber, tomatoes, and a light olive oil vinaigrette.
- Dinner (approx. 350 calories): Baked salmon fillet with a side of steamed broccoli and a small serving of quinoa.
- Hydration: Drink at least 2-3 litres of water throughout the day, as well as herbal teas or black coffee.
Comparison: 800-Calorie Diet vs. Standard Low-Calorie Diet
| Feature | 800-Calorie Diet (VLCD) | Standard Low-Calorie Diet (e.g., 1,500 kcal) |
|---|---|---|
| Calorie Intake | Approximately 800 calories per day | Approximately 1,200-1,800 calories per day |
| Weight Loss Rate | Rapid (up to 3-5 lbs per week initially) | Gradual and sustainable (0.5-2 lbs per week) |
| Recommended Duration | Short-term (typically 8-12 weeks) | Long-term, sustainable lifestyle |
| Medical Supervision | Required, especially for those with health conditions | Generally not required for healthy individuals |
| Nutrient Density | High risk of nutrient deficiencies | Easier to meet nutritional needs with balanced choices |
| Muscle Loss | Higher risk due to severe calorie restriction | Lower risk with adequate protein intake |
| Sustainability | Not sustainable long-term due to restrictiveness | More sustainable and easier to maintain |
Is the 800-Calorie Diet Right for You?
For most people, a conventional, sustainable weight loss method involving a moderate calorie reduction is safer and more effective in the long run. The 800-calorie diet is an intensive clinical intervention, not a lifestyle diet for general use. It is reserved for specific cases, such as individuals with significant obesity (BMI > 30) or type 2 diabetes who need to lose weight quickly for medical reasons, and only under the continuous supervision of a healthcare professional. It is strictly contraindicated for those who are pregnant, breastfeeding, underage, elderly, or have a history of eating disorders.
Conclusion
The 800 calorie diet is a very low-calorie approach designed for rapid weight loss, potentially offering significant metabolic benefits for specific populations like those with type 2 diabetes. However, its restrictive nature carries considerable risks, including nutrient deficiencies, muscle loss, and metabolic slowdown, making it unsuitable for most people and unsustainable in the long term. A balanced, long-term approach to nutrition and weight management is generally safer and more effective for lasting health. Any consideration of an 800-calorie diet must be initiated and overseen by a medical professional to ensure safety and mitigate risks. For more information on evidence-based dieting, it is always recommended to speak with a healthcare provider or a registered dietitian.
Explore the latest findings on Very Low-Calorie Diets in Clinical Practice.
