Eating every other day is one form that intermittent fasting can take. With this protocol, you eat normally one day and apply a significant caloric restriction the next day: either you eat nothing that day (strict protocol), or you greatly reduce your intake, for example by 75%. This second version, modified, seems more easily acceptable.
According to a summary of nine studies, this fast, strict or more flexible, practiced over a period of 3 to 12 weeks, allows, in people of normal weight, overweight or obese:
- to lose between 3 and 7% of the initial weight
- a loss of body fat of 3 to 5.5 kg
- reduce cholesterol levels by 10 to 21% and triglycerides by 14 to 41%
However, just like with the 16/8 fast, attention must be paid to the quality of the diet. Thus, a study published in 2020 shows that people who plan to fast the next day tend to anticipate by eating more and exerting less physical effort the day before. This is why this type of fasting could fail in some people. When properly conducted, this type of intermittent fasting still offers very interesting benefits.
The benefits of alternate day intermittent fasting
Researchers conducted a clinical trial to determine the effects of strict alternate-day fasting for four weeks in 60 healthy, non-obese people. They noticed :
- an improvement in health status markers, particularly in the cardiovascular field
- a reduction in body weight of 4.5%, the amount of fat mass in the trunk and an improvement in the ratio between fat mass and lean mass
- a drop in the level of methionine, an amino acid that promotes aging, on days of food deprivation
- increased levels of polyunsaturated fatty acids
Even if the participants partially compensate for the lack of food the day before on the day when they can eat, fasting every other day allows a 37% reduction in caloric intake, which is still very significant.
Intermittent fasting helps obese people lose weight
Similar effects were seen in a small study of 16 obese people, who practiced a modified version of this type of fast for eight weeks. On fasting days, participants could consume 25% of their normal energy intake. There was good adherence to this diet (more than 85%).
On average, the participants lost weight, at a constant rate of about 0.7 kg per week, which gave an average of 5.6 kg over the eight weeks (5.8% of the starting weight on average). Body fat percentage decreased, as well as systolic blood pressure.
These results suggest that this diet, with caloric restriction every other day, improves the cardio-metabolic parameters of obese or overweight people. Being able to eat as usual every other day makes this type of diet more acceptable than calorie restriction applied every day of the week, with similar benefits for weight.
Note also that this format of intermittent fasting is well tolerated, even when it lasts more than 6 months; it does not weaken immune function, unlike low-calorie diets.
Intermittent Fasting 5:2
Intermittent 5:2 fasting consists of fasting for two days, consecutive or not, during the week, and eating normally for the other five days. On fasting days, the consumption of a small amount of food – around 600 calories – is generally permitted.
This formula is well suited to people for whom it is difficult to deprive themselves every day.
The Benefits of Fasting 5:2
In a study published in 2016, the 5:2 fast was compared, over a period of 12 weeks, to calorie restriction with daily intakes of between 1200 and 1500 calories. 5:2 fasting has been shown to be as effective as continuous calorie restriction in facilitating weight loss and blood sugar control in overweight or obese people with type 2 diabetes.
In this experiment, the two weekly fasting days were not consecutive. However, this fast seems particularly effective if the two days of fasting follow each other during the week.
Thus, in a British study published in 2018, 27 overweight or obese people followed:
- or continuous calorie restriction, during which participants reduced their energy intake by 23%
- i.e. a 5:2 fast, with two consecutive fasting days: participants consumed 630 calories for two days and ate normally on the other days, which reduced their energy intake by 22%
In both groups, participants took a similar time to lose 5% of their weight, suggesting that a 5:2 diet is equivalent to calorie restriction practiced every day of the week. However, 5:2 fasting has been shown to be more effective at reducing lipids (triglycerides) in the blood.
Which form of intermittent fasting to choose?
In studies that aim to assess the effects of intermittent fasting, the experiments and measurement conditions vary somewhat. However, we note that the benefits on health and weight loss are generally similar, regardless of the mode of application chosen.
As such, choosing one intermittent fasting format over another is mostly a matter of comfort and personal preference. Do not hesitate to test these different formats, before settling on the one that best suits your lifestyle.
