The 800 Calorie Diet South Africa: Dr Mosley's Blood Sugar Diet and Fast 800 Explained

If you have been researching ways to lose weight quickly or to bring your blood sugar under control, you have probably stumbled across Dr Michael Mosley's 800-calorie approach. It goes by two slightly different names — the Blood Sugar Diet and the Fast 800 — but both are built on the same idea: a short, intensive period of eating just 800 calories (roughly 3 350 kilojoules) per day, following a Mediterranean-style food pattern, to trigger meaningful fat loss and metabolic improvement. Given that nearly 70% of South African adults are overweight or obese and that type 2 diabetes rates are rising sharply in the country, it is a protocol that deserves a clear, honest look.

What Is the 800 Calorie Diet?

The 800-calorie diet is a very low calorie diet (VLCD) that restricts daily food intake to 800 calories or fewer. What sets Mosley's version apart from generic VLCDs is the quality of those calories: rather than meal-replacement shakes alone, he advocates real, whole foods with a strong Mediterranean flavour. Think grilled fish, olive oil, leafy greens, eggs, legumes, Greek yoghurt, and a moderate amount of nuts. Refined carbohydrates, sugar, and ultra-processed foods are minimised from day one.

Mosley published the Blood Sugar Diet in 2015 after his own diagnosis with type 2 diabetes prompted him to investigate the research of Professor Roy Taylor at Newcastle University. Taylor's work showed that significant calorie restriction could drain fat from the liver and pancreas, allowing insulin-producing beta cells to recover function. For people with relatively recent type 2 diabetes, the results were remarkable. Mosley then updated and expanded the approach in the Fast 800 (2019), incorporating more flexibility and a greater emphasis on time-restricted eating.

The DiRECT Trial: Why the Evidence Matters

The strongest scientific support for this style of eating comes from the DiRECT (Diabetes Remission Clinical Trial), a large UK study published in The Lancet in 2018. Participants with type 2 diabetes followed an intensive low-calorie programme for three to five months. After one year, nearly half of those in the intervention group achieved remission of their diabetes without medication. After two years, roughly a third maintained that remission. These are striking numbers for a condition that has traditionally been described as progressive and lifelong.

It is important to be precise about what "remission" means here: it does not mean cured. It means blood glucose levels returned to a non-diabetic range and stayed there without diabetes medication. Long-term maintenance requires continued effort. Still, for South Africans managing type 2 diabetes or prediabetes, the DiRECT findings are worth discussing with your doctor or a registered dietitian.

Blood Sugar Diet vs Fast 800: What Is the Difference?

The two programmes share a foundation but differ slightly in structure:

• The Blood Sugar Diet focuses primarily on people with type 2 diabetes or prediabetes. It recommends eight weeks at 800 calories per day, followed by a Mediterranean-style maintenance phase.
• The Fast 800 is broader in scope. It offers three pathways: a two-to-twelve-week intensive phase at 800 calories daily, a 5:2-style approach where you eat 800 calories on two days a week and follow a Mediterranean diet on the other five (a form of the 5:2 diet), and a flexible maintenance path based on time-restricted eating and Mediterranean eating.
• The 5:2 variant is particularly appealing for people who find daily restriction too demanding. On the two fast days you eat 800 calories; on the remaining five you eat normally but sensibly. This approach produces slower weight loss than the intensive phase but may be more sustainable over months.

In practice, the choice between them depends on your goals. If blood sugar control is your primary concern, the stricter daily 800-calorie phase is more likely to produce rapid results. If you are looking for gradual, steady weight loss with a lower risk of feeling deprived, the 5:2 variant gives you more breathing room.

What a Day of Eating Looks Like at 800 Calories in South Africa

One of the most common questions is whether 800 calories can actually feel like real food. The answer is yes, provided you choose high-volume, high-protein, high-fibre options and keep refined starches off the plate. Here is a practical example using foods readily available at Checkers or Pick n Pay:

That is an entire day of food for under R110, which is competitive with many fast-food lunches alone. Checkers and Pick n Pay both stock hake fillets, canned legumes, and fresh vegetables at reasonable prices, making the Mediterranean-leaning food pattern genuinely accessible in South Africa, even outside major metros. Black-eyed beans, lentils, and chickpeas from the canned aisle are particularly useful protein and fibre sources that keep costs low.

How Does 800 Calories Compare to Other Approaches?

Who Is the 800 Calorie Diet Best Suited To?

This approach is not for everyone, but there is a clear group of people for whom it may be worth exploring with a doctor:

• Adults with type 2 diabetes or prediabetes who want to target blood sugar control quickly alongside weight loss.
• People who prefer a defined, time-limited intensive phase over months of slow, gradual calorie reduction.
• Those who have tried standard calorie restriction and found the slow pace of results demotivating.
• People who want to follow a Mediterranean-style whole-food diet rather than relying on meal replacement shakes.
• Individuals with a BMI above 27 who have no contraindications and can access regular medical monitoring while following the plan.

If blood sugar medication is part of your daily routine, this is especially important: rapid calorie restriction can cause blood glucose to drop sharply, and medication doses may need to be adjusted by your doctor before you start. The same applies to blood pressure medication. South African endocrinologists and dietitians are increasingly familiar with the DiRECT-style approach, and a growing number of GP practices are offering structured low-calorie programmes alongside standard diabetes care.

Who Should NOT Follow the 800 Calorie Diet

Practical Tips for Following the 800 Calorie Diet in South Africa

• Track kilojoules, not just calories. South African food labels display kilojoules (kJ). To convert: 800 calories equals approximately 3 350 kJ. Most supermarket packaging will list kJ values per 100 g and per serving.
• Prioritise protein at every meal. Eggs, tinned fish (Lucky Star pilchards and tuna are good-value staples), legumes, low-fat cottage cheese (Lancewood), and Greek-style yoghurt all help maintain muscle mass and keep you fuller for longer on a restricted intake.
• Load your plate with non-starchy vegetables. Baby spinach, broccoli, cauliflower, courgette, green beans, mushrooms, and tomatoes are low in calories and high in volume. A large salad or a bowl of roasted vegetables can take the edge off hunger at minimal calorie cost.
• Use olive oil sparingly but do use it. One teaspoon (about 40 calories) adds flavour, supports fat-soluble nutrient absorption, and aligns with the Mediterranean pattern that underlies the approach. Checkers and Pick n Pay both stock affordable South African olive oils.
• Drink plenty of water and herbal tea. Thirst is often mistaken for hunger. Rooibos tea is calorie-free, widely available, and genuinely good for you.
• Plan your fast days in advance. If you are following the 5:2 variant, decide the night before what you will eat on your fast day so you are not improvising when hungry.
• Expect the first week to be the hardest. Most people report that hunger and low energy during the first five to seven days improve significantly as the body adapts. Headaches and irritability in week one are common; staying well-hydrated helps.

The Mediterranean-Style Connection

What makes Mosley's 800-calorie approach different from a generic crash diet is the emphasis on food quality. Both the Blood Sugar Diet and the Fast 800 draw heavily on the Mediterranean dietary pattern: plenty of vegetables, olive oil, fish, legumes, nuts, and some dairy, with minimal processed food, sugar, and white starch. This is not arbitrary. The Mediterranean diet is one of the most studied dietary patterns in the world and is consistently associated with lower rates of heart disease, type 2 diabetes, and certain cancers. Building an 800-calorie restriction phase around Mediterranean foods means that even at a very low calorie level, you are still getting a broad range of micronutrients, healthy fats, and anti-inflammatory compounds.

From a practical South African standpoint, the Mediterranean approach is more affordable than many people assume. Canned legumes, eggs, frozen fish, and seasonal vegetables are cost-effective foundations. Where the budget allows, a small amount of olive oil and a handful of nuts each day round out the nutritional profile without adding too many calories.

What Happens After the 800 Calorie Phase?

Mosley is clear that the intensive phase is a launchpad, not a permanent way of eating. After the initial 8-to-12-week period (or shorter, depending on your goals and medical situation), the plan transitions to a Mediterranean-style maintenance approach, sometimes combined with time-restricted eating (for example, eating within a 10- to 12-hour window each day). The goal is to sustain the metabolic improvements gained during the restriction phase while returning to a more varied and flexible diet that is realistic for the long term.

Weight regain is a real risk if the post-diet period is not handled carefully. Working with a registered dietitian during and after the intensive phase is the most reliable way to maintain results.

Always consult a registered dietitian or healthcare provider before making significant dietary changes, especially if you are managing a chronic condition.