6 Intermittent Fasting Protocols Compared: Which One Is Best?
By R.Davies, PhD・Fasting
Published on May 06, 2026
Intermittent fasting is not one diet — it is a family of (slightly) different eating 'patterns' that share a common principle: periods of not eating followed by periods of normal eating. This article explains the main types of intermittent fasting out there. We’ll cover the science behind each one and explain how to choose the one that best fits your goals and lifestyle. So, if you have decided to try intermittent fasting, the first problem you’ll run into is which one?
There are a few options: “16:8”, “5:2”, “alternate day fasting”, “one meal a day” or “time-restricted eating”. The terminology can be confusing, and the claims for each type vary wildly. Some people simply call what they are doing intermittent fasting when really they're talking about one specific protocol.
This article aims to help you understand all the main types on offer and which one’s best for you. There is no single “best” type of intermittent fast, but some are better than others, and some suit certain people, while others don’t.
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What Counts as Intermittent Fasting?
Different intermittent fasting protocols vary in how often you fast, how long you fast for, and how strict the fast is, meaning what or how many calories you’re allowed to eat during the 'fasting period'. Most intermittent fasting protocols are grouped under two branches:
- Time-restricted eating: where you eat within a defined daily window and then fast for the rest of the day.
- Periodic fasting: where you eat normally on some days and then fast, or significantly reduce your calories, on other days of the week.
Both types trigger the same underlying “fasting response”, which includes falling insulin levels and increased fat burning. However, most people tend to prefer one approach over another [1].
Time-Restricted Eating
The basic principle of time-restricted eating is that you eat all your food within a set number of hours each day, then fast for the rest. Here are the main types:
“12:12” — 12 hours eating, 12 hours fasting
This is the entry-level version. For many people, it is already their default eating pattern (e.g., finishing their last meal of the day at 8 pm, eating breakfast at 8 am). There is limited specific research on 12:12, but it's a reasonable starting point for beginners and serves as a gentle introduction to intermittent fasting. The benefits of this type of fast are really more about establishing a fixed eating schedule and cutting out the late-night snacks (which derail your sleep).
“14:10” — 14 hours fasting, 10 hours eating
This is the next step up. It is typically achieved by skipping a late-night snack or delaying breakfast slightly (by an hour or so). Some evidence suggests that 14-hour fasting windows may begin to produce measurable improvements in metabolic health markers, although most research is generally focused on longer fasting windows [1].
“16:8” — 16 hours fasting, 8 hours eating
This is the most researched time-restricted eating protocol and, for most people, the practical “sweet spot”: balancing practicality with the health benefits. A typical pattern is eating between noon and 8 pm, then fasting overnight and through the morning til noon the following day.
Studies consistently show that 16:8 fasts help people lose weight by reducing overall calorie intake [2]. There are also some metabolic health benefits as well (e.g., improved insulin sensitivity, reduced blood pressure, improved blood lipid profile) [3].
In addition to the length of the window, the timing of the window also seems to matter as well. Earlier eating windows (e.g., 8 am to 4 pm, or earlier) generally produce better weight loss and health benefits than later ones [4]. Your body tends to process food better (and more efficiently) in the morning/daylight hours than late in the evening.
“18:6” & “OMAD”
An 18:6 window (eating within 6 hours, fasting for 18) and OMAD (one meal a day, effectively a 23:1 pattern) are more extreme approaches. They extend the positive effects of fasting but also come with trade-offs. Following these longer fasts is more difficult to adhere to, and the small eating windows also make it difficult to meet your nutritional needs, particularly getting enough protein, fibre and some micronutrients in such a small eating window.
Periodic Fasting
Rather than restricting the hours during which you eat each day, 'periodic fasts' assign specific fasting (or low-calorie) days across the week.
“5:2” — Five Normal Days + Two Restricted Days
The 5:2 diet involves eating normally five days and restricting calories on two non-consecutive days, typically to around 500–600 calories. It is popular partly because of its flexibility: you only need to manage two difficult days, and those days can be scheduled around your week.
Studies show that the “5:2” approach produces similar weight loss to time-restricted eating and normal calorie-restriction diets [5]. However, the main advantage of the 5:2 pattern is its flexibility and reduced 'mental workload'. Meaning some people find it more manageable to endure two “strict days” a week, compared to maintaining eating restrictions every day of the week.
Again, the main disadvantage is that the fasting days are more difficult and uncomfortable compared to other types of fasts. Hunger, low energy and difficulty with work or concentrating are all commonly reported.
“Alternate-Day Fasting” — Fasting Every Other Day
As the name states, alternate-day fasting involves alternating between restricted days and unrestricted days after another. In its strictest form, the 'fasting days' mean no food whatsoever. However, some protocols allow a small amount of food (around 500 calories) on the fasting days.
As you can imagine, alternate-day fasts generally lead to the quickest, most effective weight loss (and some health benefits) in the short-term [5][6]. However, just like the 5:2 fasts, the longer and more frequent fasting periods are generally more difficult to maintain.
Researchers report that participants in their studies were around three times more likely to give up on 5:2 and alternate-day fasts compared to time-restricted eating or just normal calorie-restricted diets [5].
Beyond Intermittent Fasting: Other Fasting Protocols
Extended Fasting (24–72+ hours):
These longer fasting periods trigger different physiological responses: ketosis, autophagy and measurable changes in your hormone levels. Extended fasts are not routinely recommended for weight loss and general health, as they carry extra medical risks and should be medically supervised.
Fasting-Minicking Diet:
This is a 5-day cycle of a very-low-calorie diet, but eating certain nutrient-dense foods, mainly plants. This protocol is designed to “mimic” the physiological effects of fasting but without entirely avoiding food. It is generally done less frequently (e.g., once a month or less) than other types of fasts, but there is some promising research on it [7].
Religious and Cultural fasts:
People have been fasting for centuries. It is not a new thing at all. Fasts are routinely undertaken in many religions, with a lot of them resembling similarities to intermittent fasting protocols. However, because these types of fasts aren’t specifically designed for health reasons and they're also combined with other religious practices (which may or may not be good for health), we don't recommend them.
Intermittent Fasts Compared
Alternate-day fasts produce the most obvious changes in body weight and health markers, but they are more difficult to follow, and questions have been raised about how sustainable they are. Whereas the 16:8 fasts are easier to follow and possibly just as good (or are better) than more demanding protocols, when you consider drop-out rates, and their real-world compatibility.
If you’re now thinking about trying time-restricted eating (like the 16:8 protocol), consider adopting earlier time windows, so you start your eating window earlier in the day (7-10 pm), as it has better health and weight loss outcomes. However, some people might prefer a periodic 5:2 eating pattern, where they only have to think about when (and what) they are eating two days a week.
In general, the best protocol is one you are going to stick to.If you’re new to fasting, you’re probably better off starting with the easier protocols, like the 14:10 or 12:12, for a few weeks before trying longer fasts. If you have a pretty regular daily routine and don’t mind a late breakfast or early dinner, the 16:8 protocol is a natural fit, as it balances flexibility, is relatively easy to follow, is well-studied and sustainable for most people.
6 Practical Tips
1. A big mistake is thinking that, because you’ve fasted, you can then eat whatever you want in your eating window. This is not recommended. Keeping your eating window nutritionally solid is needed for success. You can’t fast your way out of a poor diet. You should consider nutrient-rich foods (and avoid junk foods) in your eating window. Pay special attention to getting enough protein and dietary fibre.
2. Drink plenty of water. The hunger during fasting can sometimes inadvertently lead to dehydration. Water, plain coffee and teas are perfectly fine and encouraged to consume while you're in your fasting windows. You want to keep an eye on how much you’re drinking.
3. Manage your hunger. Some people can naturally skip (or delay) meals without any issues, whereas other people need some time to get used to going without eating. There seems to be an adaptation period, with most people taking a few weeks to get used to fasting for longer than they are used to [7]. If the first few days feel hard, try to stick with it for a bit longer and see if it gets easier after a week or two.
4. Exercise complements fasting — it improves all the health benefits, can mitigate some of the negative effects of fasting, and some types of exercise can actually reduce your appetite, making it easier to stick to.
5. Be honest about your lifestyle and other commitments. A protocol that works on paper but causes issues with planning meals, your work schedule or social life is more likely to fail. Factor in your actual life, not your idealised one.
6. Review and adjust periodically. Intermittent fasting is not a lifetime commitment to one fixed eating pattern. Start with a manageable protocol, assess how you feel and what results you're seeing after 2-3 months, and adjust accordingly. Some people find they naturally settle into a shorter window; others progress to longer fasting periods over time.
Key Takeaways
All of the standard intermittent fasting protocols have been shown to produce meaningful improvements in body weight and health when followed correctly and consistently. There is no clear winner that outperforms all others across all measures and timeframes. If you want to try intermittent fasting, the best protocol is one that fits your own biology, goals, lifestyle, and one you can actually follow.
No expert can tell you exactly what type of eating pattern will work best for each person. But if you’re after a balance of all the positive benefits (including how flexible and easy it is to follow), the early window 16:8 pattern just pips it in our opinion. However, several others work equally as well and may suit some people better than others.
Sources
1. Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 2017 Aug 21;37:371-393. PMID: 28715993
2. Elortegui Pascual P et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity (Silver Spring). 2023 Feb;31 Suppl 1(Suppl 1):9-21. PMID: 36349432
3. Varady KA, Cienfuegos S, Ezpeleta M, Gabel K. Cardiometabolic Benefits of Intermittent Fasting. Annu Rev Nutr. 2021 Oct 11;41:333-361. PMID: 34633860
4. Liu J, Yi P, Liu F. The Effect of Early Time-Restricted Eating vs Later Time-Restricted Eating on Weight Loss and Metabolic Health. J Clin Endocrinol Metab. 2023 Jun 16;108(7):1824-1834. PMID: 36702768
5. Elortegui Pascual P et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity (Silver Spring). 2023 Feb;31 Suppl 1(Suppl 1):9-21. PMID: 36349432
6. Wang B et al. The impact of intermittent fasting on body composition and cardiometabolic outcomes in overweight and obese adults: a systematic review and meta-analysis of randomized controlled trials. Nutr J. 2025 Jul 30;24(1):120. PMID: 40731344
7. Wei M et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Sci Transl Med. 2017 Feb 15;9(377):eaai8700. PMID: 28202779
8. Seimon RV et al. Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Mol Cell Endocrinol. 2015 Dec 15;418 Pt 2:153-72. PMID: 26384657
Published: May 06, 2026
Lead Author: R.Davies, PhD | Author Bio
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