Different Types of Intermittent Fasting Compared: Which One Is Best?
There’s no single "best" type of intermittent fasting. However, there is probably one that suits your goals and life best.
- Earlier eating windows consistently produce better weight loss and metabolic health outcomes than later windows of the same duration.
- Alternate-day fasting and 5:2 fasting protocols had higher drop-out rates than time-restricted eating.
- All major intermittent fasting protocols produce similar weight loss when they are adhered to, so pick one you'll follow.
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.
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 another1.
Time-restricted eating: daily fasting windows
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 fasting: the beginner's starting point
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 fasting: the next step up
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 windows1.
16:8 fasting: the most popular protocol
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 intake2. 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 ones4.
Your body tends to process food better (and more efficiently) in the morning/daylight hours than late in the evening.
18:6 and OMAD (one meal a day)
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.
The longer fasts tend to be 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: whole-day and multi-day approaches
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 fasting: the most flexible option
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 diets5. However, the main advantage of the 5:2 pattern is its flexibility and reduced 'mental workload'. 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-term5,6. 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 diets5.
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 it7.
We've done a full review and sample menu of the fasting mimicking diet.
Dr. Robert Davies
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.
