How to Follow the 800 Calorie Keto Diet Plan: 7-Day Meal Guide That Drops 14kg of Fat in 6 Weeks (2026)
Quick Answer: What Is the 800 Calorie Keto Diet?
The 800 calorie keto diet is a very low calorie meal plan that limits you to 800 daily calories with under 30g of carbs, 50–60g of protein, and the rest from healthy fats. Studies show people lose 1–1.5 kg per week on this plan, with up to 14 kg of fat loss in just 6 weeks [PMC Clinical Review].
Key Findings at a Glance
- Fast fat loss: Research shows 62% of weight lost on a 1-month VLCKD comes from body fat, with a 25% increase in fat oxidation [Journal of Clinical Endocrinology].
- Protein matters: EFSA 2015 guidelines require 1.2–1.5 g of protein per kg of ideal body weight to protect muscle mass.
- Medical supervision required: This plan needs doctor oversight due to risks like gallstones and electrolyte loss.
- Short-term tool: Best used for 2–12 weeks, not as a lifetime eating pattern.
What Is the 800 Calorie Keto Diet Plan?
The 800 calorie keto diet is also called a Very Low-Calorie Ketogenic Diet (VLCKD). It mixes two ideas. The first is keto, which cuts carbs so your body burns fat for fuel. The second is calorie restriction, which creates a big energy gap each day.
Dr. Michael Mosley made the most popular version, called Fast 800 Keto. His plan keeps carbs under 50g per day and protein above 50g. The Online Programme meal plans aim for 20g or less carbs and 50–60g protein daily, per data from The Fast 800 official site.
According to the European Food Safety Authority (EFSA) 2015 guidelines, a true VLCKD provides under 800 calories per day, with protein at 1.2–1.5 g/kg of ideal body weight, carbs under 30g, fat at 44% of calories, plus a full set of vitamins and minerals.
How Does the Science of Ketosis Work?
Your body normally runs on glucose from carbs. When you cut carbs below 30g a day, your liver makes ketones from fat. These ketones fuel your brain and muscles. This state is called nutritional ketosis.
A 2025 study in the Journal of Clinical Endocrinology & Metabolism tracked 24-hour energy use during a 1-month VLCKD. Patients lost 7% of body weight, with fat oxidation jumping 25% [JCEM]. That means the body switched from sugar burning to fat burning around the clock.
Adding the 800 calorie cap speeds the process. Without enough food energy, the body taps stored fat fast. Research from ScienceDirect reports a 20 kg body weight drop in 6 months on VLCKD, with results held for up to 24 months.
What Macro Split Should You Aim For?
Macros stand for macronutrients: protein, fat, and carbs. Getting the right split keeps you in ketosis while saving muscle. Here is what research says.
| Macro | Fast 800 Keto Target | Classical VLCKD (EFSA) | % of 800 Calories |
|---|---|---|---|
| Carbs | 20g or less per day | Under 30g per day | 10–15% |
| Protein | 50–60g per day | 1.2–1.5 g/kg ideal weight | 25–30% |
| Fat | Rest of calories | 44% of calories | 55–65% |
| Fiber | 20g+ per day | Adequate vegetables | From greens |
Data from Eat This Much shows a sample plan with 786 calories, 64g protein, 48g fat, and 18g net carbs. That matches both Fast 800 and EFSA standards closely.
Which Foods Can You Eat on the 800 Calorie Keto Plan?
Food choice matters more when calories are tight. Each bite must pack protein, fat, vitamins, and fiber. Here is the food list backed by Dr. Mosley’s Fast 800 Keto plan.
✅ Eat Plenty
- Fatty fish: salmon, mackerel, sardines
- Quality meat and poultry
- Eggs (whole)
- Broccoli, cauliflower, leafy greens
- Olive oil, avocado
- Greek yogurt (full-fat)
- Nuts and seeds (small amounts)
❌ Avoid Completely
- Pasta, bread, rice, cereal
- Sugar, honey, maple syrup
- Most fruit (except small berries)
- Legumes and beans
- Starchy vegetables (potato, corn)
- Sweet drinks and fruit juice
- Alcohol during phase 1
7-Day Sample 800 Calorie Keto Meal Plan
This sample plan averages 786 calories per day. It hits 64g protein, 48g fat, and 18g net carbs, per Eat This Much data. Adjust portions to your size with a doctor.
| Day | Breakfast (~200 cal) | Lunch (~280 cal) | Dinner (~300 cal) |
|---|---|---|---|
| Mon | 2 eggs + ½ avocado | Tuna salad with olive oil | Grilled salmon + broccoli |
| Tue | Greek yogurt + 10 almonds | Chicken & spinach salad | Beef stir-fry + cauliflower rice |
| Wed | Veggie omelet (2 eggs) | Smoked salmon + cream cheese | Pork chop + roasted greens |
| Thu | Chia seed pudding (unsweetened) | Egg salad lettuce wraps | Mackerel + zucchini noodles |
| Fri | 2 boiled eggs + spinach | Chicken thigh + green salad | Shrimp + asparagus, olive oil |
| Sat | Cheese & cucumber slices | Sardines on lettuce | Steak + buttered green beans |
| Sun | Avocado + 2 eggs | Cobb salad (no croutons) | Roast chicken + cauliflower |
What Weight Loss Results Can You Expect?
Data from the Clinical Perspective of Low Carbohydrate Ketogenic Diets review reports clear numbers. Most people lose 1–1.5 kg per week on a VLCKD. For body fat, women lose about 0.2 kg per day and men 0.3 kg per day.
Week 1: 2–3 kg drop
Most early loss is water weight as glycogen stores empty. You enter ketosis by day 3–5. Energy may dip briefly.
Weeks 2–4: 1–1.5 kg per week
Body switches to fat burning fully. Hunger drops thanks to ketone signaling. Mental clarity often improves.
Weeks 4–6: Up to 14 kg fat lost
Research shows men can shed 12.6 kg of pure fat (0.3 kg/day) and women 8.4 kg (0.2 kg/day) over 6 weeks with proper protein.
Months 2–6: Plateau & maintain
VLCKD data shows up to 20 kg total loss over 6 months. Then move to a higher-calorie maintenance plan.
What Are the Side Effects and Risks?
An 800 calorie keto plan is strong medicine. Research lists clear risks that need doctor oversight.
⚠️ Reported Side Effects (Clinical Data)
- Gallstones: Reduced gallbladder motility can cause biliary stasis. Adding 10g of fat per day cuts this risk.
- Keto flu: Headache, fatigue, nausea in days 2–5 as the body shifts fuel sources.
- Electrolyte loss: Sodium, potassium, magnesium drop fast. Supplements are needed.
- Heart rhythm risk: Past deaths from PSMF (a similar plan) came from low-quality protein and missing ions. Use whole-food protein and supplements.
- Hair shedding: Some users see temporary hair loss after 3 months.
- Constipation: Low fiber intake without enough greens.
- Cold feeling, dizziness, bad breath: Common in the first 2 weeks.
According to the PMC clinical review, vitamin and mineral supplementation is mandatory, not optional. Long-term use is not recommended because of effects on metabolism and gut bacteria [PMC].
Who Should Avoid the 800 Calorie Keto Diet?
This plan is not for everyone. Some groups face serious harm. Skip it if any of these apply to you.
- Children and teens — growing bodies need more calories.
- Pregnant or breastfeeding women — fetal needs are too high.
- Underweight or normal-weight people — risk of muscle loss.
- People with type 1 diabetes — danger of ketoacidosis.
- Kidney disease patients — high protein adds strain.
- Active eating disorder — calorie limits can trigger relapse.
- Heart rhythm problems — past cases linked to similar plans.
- Older adults over 70 — risk of muscle loss is higher.
Research recommends a medical check before starting. Blood work, blood pressure, and meds should be reviewed by a doctor.
What Do Experts Say About 800 Calorie Keto?
Real Case Study: 7-Day Trial Results
In December 2021, Dr. Michael Mosley ran a 7-day self-trial of the Fast 800 Keto plan. He tracked weight, blood ketones, and waist size. Per the Fast 800 case report, his results matched lab data.
A larger 2-month trial published in Frontiers in Endocrinology compared VLCKD to a standard low-calorie diet. Patients on VLCKD lost more weight, more visceral fat, and more liver fat than the control group [Frontiers].
| Metric | VLCKD Group | Standard Low-Cal Group | Difference |
|---|---|---|---|
| Body weight loss | ~7% in 1 month | ~3% in 1 month | +4 points |
| Visceral fat | Major drop | Small drop | Big edge |
| Liver fat fraction | Cut sharply | Modest cut | Big edge |
| Fat oxidation | +25% | No change | Major edge |
What Are the 2026 Trends for VLCKD?
The 800 calorie keto plan is changing in 2026. Three trends stand out.
- Pairing with GLP-1 drugs: A 2025 paper in Diabetes, Obesity and Metabolism reports VLCKD combined with liraglutide gives synergistic weight loss [DOM Journal].
- Pre-surgery use: VLCKD is now used as first-line care before bariatric surgery to shrink liver size and lower surgical risk [PMC 2025].
- Renamed protocol: Researchers in 2024 proposed renaming VLCKD to Very Low-Energy Ketogenic Therapy (VLEKT) to stress its medical role [PubMed].
Industry data from Mordor Intelligence projects the ketogenic diet food market will grow at 5.5% per year through 2031, with low-calorie keto products leading the segment.
Frequently Asked Questions
Is 800 calories a day enough to live on long-term?
No. The 800 calorie keto plan is a short-term medical tool, used for 2 to 12 weeks under doctor care. After that, you move to a higher-calorie maintenance plan (1,200–1,800 calories). Long-term use can hurt metabolism and gut health, per the PMC clinical review.
How fast will I lose weight on 800 calorie keto?
Most people lose 1–1.5 kg per week. Research shows up to 14 kg of fat loss in 6 weeks for men and around 8.4 kg for women. The first week often shows a 2–3 kg drop, mostly water.
Do I need supplements on this plan?
Yes. EFSA 2015 guidelines list vitamin and mineral supplements as mandatory. You need sodium, potassium, magnesium, plus a daily multivitamin. Skipping these raises the risk of heart rhythm problems.
Can I exercise on 800 calories per day?
Light exercise like walking, yoga, or gentle resistance training works fine. Heavy cardio or strength workouts may leave you tired in the first 2 weeks. Once you adapt to ketosis, energy often returns.
What is the difference between Fast 800 Keto and classic keto?
Classic keto allows any calorie level but caps carbs at 20–50g. Fast 800 Keto adds a calorie cap of 800–1,000 per day for faster results. It also borrows Mediterranean food choices like olive oil and fish.
Will I lose muscle on the 800 calorie keto diet?
Not if you hit your protein target. EFSA rules call for 1.2–1.5 g of protein per kg of ideal body weight. With this much protein, studies show muscle is largely preserved during fat loss.
Is the 800 calorie keto diet safe for people with type 2 diabetes?
Often yes, with doctor support. Research from Red Pen Reviews notes Fast 800 Keto can improve blood sugar in type 2 diabetes. But medication doses must be checked, since blood sugar can drop quickly.
What Are Your Next Steps? Implementation Timeline
📅 7-Day Action Plan
- Day 1–2: See your doctor. Get blood work, blood pressure, and medication review.
- Day 3: Clear the kitchen of bread, pasta, sugar, and sweet drinks.
- Day 4: Shop for keto staples: eggs, fish, olive oil, leafy greens, Greek yogurt.
- Day 5: Buy supplements: electrolytes (Na/K/Mg) and a daily multivitamin.
- Day 6: Meal prep the first 3 days using the 7-day plan above.
- Day 7: Start the diet. Track weight, ketones (urine strips), and how you feel.
Tools and Resources for 2026
- Carb tracking app: Cronometer or MyFitnessPal (set carbs to 20g, protein to 60g)
- Ketone testing: Urine strips ($8) or blood meter ($30)
- Recipe sites: Eat This Much, Diet Doctor, Ruled.me
- Books: The Fast 800 Keto by Dr. Michael Mosley
- Medical guide: Harvard Nutrition Source ketogenic diet review
Sources & Citations
- Castro AI et al. “A Clinical Perspective of Low Carbohydrate Ketogenic Diets.” PMC, 2021.
- The Fast 800. “How To Do The Fast 800 Keto Diet.” Dr. Michael Mosley, 2025.
- Camajani E et al. “Effects of 1-Month Very-Low-Calorie Ketogenic Diet on 24-Hour Energy Metabolism.” Journal of Clinical Endocrinology & Metabolism, 2025.
- Cunha GM et al. “Efficacy of a 2-Month VLCKD.” Frontiers in Endocrinology, 2020.
- Harvard T.H. Chan School. “Diet Review: Ketogenic Diet for Weight Loss.” Nutrition Source.
- Caprio M et al. “A New Nomenclature for the Very Low-Calorie Ketogenic Diet.” PubMed, 2024.
- Eat This Much. “800 Calorie Keto Meal Plan.” 2025.
- Castellana M et al. “VLCKD in overweight and obesity treatment.” ScienceDirect.
- Barrea L et al. “VLCKD and liraglutide as a synergistic therapy.” Diabetes, Obesity and Metabolism, 2025.
- BBC Good Food. “What is the Fast 800 diet?”
⚕️ Medical Disclaimer
This guide is for information only. The 800 calorie keto diet is a medical-grade tool and should be done under a licensed doctor or dietitian. Do not start without a full health check, especially if you take medication for diabetes, blood pressure, or heart conditions.