Sweet Potato and The Fast 800: Understanding the Compatibility
The Fast 800 diet, developed by Dr. Michael Mosley, is a lifestyle approach that emphasizes a low-sugar, moderately low-carb, Mediterranean-style eating plan. It incorporates different phases, including the more intense Very Fast 800 (consuming 800 calories daily) and the New 5:2 (800 calories on two days per week). The core principle is to manage blood sugar and insulin levels to promote weight loss and metabolic health. So, where does the starchy sweet potato fit in?
The Impact of Carbohydrates and the Glycemic Index
Sweet potatoes are a nutritious food, rich in complex carbohydrates, fibre, beta-carotene, and essential vitamins and minerals. However, their carbohydrate content means they can significantly impact blood sugar levels, which is a key metric on the Fast 800. For this reason, the program prioritizes non-starchy vegetables during the more restrictive phases. The glycemic index (GI), a ranking of how quickly a food raises blood sugar, is the crucial metric here. The cooking method of a sweet potato dramatically alters its GI value.
How Cooking Method Affects Sweet Potato on The Fast 800
- Boiling: This is the most favourable method for Fast 800 followers. When boiled for 30 minutes, sweet potatoes have a low GI of approximately 46. Longer boiling times can lower the GI further, making it a safer option for blood sugar management.
- Steaming: This method also results in a moderate GI, making it a better option than baking or roasting.
- Baking/Roasting: When baked for 45 minutes, a sweet potato's GI can reach up to 94, putting it on par with instant mashed potatoes and white bread. The roasting process destroys resistant starch, leading to a much higher GI. This is generally discouraged on Fast 800, especially during the intensive phases.
- Frying: Frying sweet potatoes also results in a high GI of around 76 and adds unnecessary calories and saturated fat, making it an unsuitable option.
Portion Control Across Different Fast 800 Phases
- The Very Fast 800 / Keto: During the initial, most restrictive phase or the keto version, sweet potato should be largely avoided. The diet aims for a very low-carb intake (under 50g per day on Keto) to induce ketosis. The carbs in sweet potato would likely take up too much of the daily allowance. The program often recommends lower-carb vegetable alternatives instead.
- The New 5:2 / Maintenance: In these less restrictive phases, sweet potato can be included in small, controlled portions on your non-fasting days. It's still wise to opt for the boiled preparation method to keep the GI low and to be mindful of the portion size, treating it more like a garnish than a main component.
Comparison of Carb and GI Impact
| Food Item | Typical Preparation | Glycemic Index (GI) | Carb Content (approx. per 100g) | Fast 800 Suitability |
|---|---|---|---|---|
| Sweet Potato | Boiled (30 min) | ~46 (Low) | ~21g | OK in moderation (5:2/Maintenance) |
| Sweet Potato | Baked (45 min) | ~94 (High) | ~21g | Generally avoided |
| Celeriac | Roasted | N/A (Low) | ~9g | Recommended substitute |
| Carrot | Roasted | ~35 (Low) | ~10g | Recommended substitute |
| Pumpkin | Roasted | ~64 (Medium) | ~7g | OK in moderation (Mediterranean style) |
Alternatives to Sweet Potato on The Fast 800
When you need a starchy vegetable fix during the more restrictive phases, there are excellent lower-carb alternatives that fit perfectly within the program's guidelines:
- Celeriac: A versatile root vegetable with a much lower carbohydrate count.
- Parsnips: Can be roasted like a potato but are used sparingly.
- Pumpkin or Butternut Squash: Excellent for soups and curries, these are lower in carbs than sweet potato.
- Cauliflower: Can be mashed or roasted to substitute potatoes with very low carbs.
Conclusion: A Matter of Method and Moderation
To summarise, while sweet potatoes are not outright forbidden on The Fast 800, their inclusion must be strategic. During the intensive weight loss and keto phases, they are generally avoided due to their carbohydrate load and impact on blood sugar. In contrast, on maintenance or non-fasting days of the 5:2 plan, a small, controlled portion of boiled or steamed sweet potato can be an acceptable part of a balanced, Mediterranean-style meal. Prioritise preparation methods that keep the glycemic index low and always consider the specific phase of the diet you are following to ensure your metabolic health goals are met. For official recipes and guidelines, check the official Fast 800 website.
Frequently Asked Questions
1. Can I have sweet potato fries on the Fast 800 diet? No, frying sweet potatoes gives them a high glycemic index and adds excess fat, which is contrary to the Fast 800 principles of low-carb, Mediterranean-style eating.
2. Is sweet potato allowed on Fast 800 Keto? No, sweet potato is typically not allowed on the Fast 800 Keto phase. This stage requires very low carbohydrate intake (under 50g daily), and sweet potato's carb content would make it difficult to stay in ketosis.
3. Is boiled sweet potato a low GI food? Yes, when boiled for a longer period (30 minutes or more), the sweet potato has a low glycemic index, making it the most suitable preparation method for the Fast 800 diet.
4. What are good alternatives for sweet potato on Fast 800? Great low-carb alternatives include celeriac, pumpkin, butternut squash, parsnips, and cauliflower, which feature in many official Fast 800 recipes.
5. How much sweet potato can I eat on a non-fasting day? On non-fasting days (The New 5:2 or Maintenance), a small, mindful portion is acceptable. Treat it as a side dish rather than a main component, and stick to the boiled method.
6. Does the type of sweet potato matter for the GI? While some varieties may have slight differences, the cooking method has the most significant impact on the GI. Boiling will always result in a lower GI than baking or roasting, regardless of the variety.
7. What is the GI of baked sweet potato? Baked sweet potato has a high glycemic index, potentially as high as 94 when baked for 45 minutes. It should be avoided on most Fast 800 phases.
8. Can sweet potato be part of a 'cheat' meal on Fast 800? While the Fast 800 promotes a balanced, long-term lifestyle, highly processed or high-sugar foods are discouraged. If you have a planned higher-carb meal, a small portion of boiled sweet potato would be a more nutritious choice than other less-healthy options.
