Intermittent diets, more effective for weight loss, really?

Intermittent diets

everyone to get started, the Internet has been relaying this trend for several years.  However, the term “intermittent diet” covers several realities, with varied practices (see box). Their common point is always to alternate more or less long periods of food restrictions with periods when you can eat normally.

This type of diet is often presented as more effective in promoting weight loss. Some believe in particular that it makes it possible to avoid the constraints and possible frustrations linked to a continuous food restriction, and therefore that it leads to better adherence.  Others highlight beneficial effects on metabolic parameters (blood pressure, blood sugar, cholesterol, etc.), or even for the prevention of certain diseases (cancer, inflammatory, metabolic, cardiovascular diseases, etc.).

It should be noted, however, that well-constructed scientific studies, with solid methodologies, are still lacking to properly assess these diets and their effects in different populations.  Moreover, even when interesting results are obtained, it may be difficult to generalize them to all intermittent diets given the heterogeneity of practices.

So what can be said about the effect of intermittent dieting on weight loss? Are they more effective than other diets in the long term? And what is their impact on eating behavior? Canal Détox looks into these questions.

The most popular intermittent diets

The 5:2 diet consists of eating normally for 5 days and then significantly reducing the number of calories for the next 2 days (500 calories/day for women and 600 calories/day for men).

The 16/8 diet consists of fasting during the day for a period of 14 to 16 hours and having meals for the remaining 8 to 10 hours (for example, you can have a snack at 4 p.m.  and eat nothing until the next morning).

Intermittent diets are no more effective than other diets

The main promise of intermittent diets would be to facilitate weight loss while easing stress compared to other restrictive diets. But when we look at the most rigorous studies or reviews of scientific literature (meta-analyses), we realize that the results are variable. Most of the publications do not show any superiority of the intermittent diet (regardless of its modalities) compared to other diets in terms of weight loss.

Among the studies published on the subject with a rigorous methodology, let us quote some, which were particularly interested in the diet 5: 2 (5 days free and 2 days with a very reduced consumption of calories).

A study published in the International Journal of Obesity was carried out on 332 people with obesity, divided into three groups (continuous restriction with a reduction in the number of calories consumed each day; alternating restriction every other week and classic intermittent restriction 5 : 2).  After 12 months, only 146 subjects completed the study, with similar moderate weight loss in the three groups (respectively 6.6 kg, 5.1 kg and 5 kg on average).

Similar results were observed in a study of 109 subjects followed for 24 months, with similar weight loss in the first year for the three types of diets and stabilization of this weight between 12 and 24 months.  However, it is not possible from these data to draw conclusions on other types of intermittent diets.

These different studies have also looked at crucial metabolic parameters for health, particularly cardiovascular, without succeeding in showing the superiority of one diet over the others.  In studies comparing the 5:2 diet to more traditional restrictive diets, for example, while overall cholesterol decreased, blood glucose levels and triglycerides [1] remained unchanged in all groups.  Similarly, in the study comparing these diets to an unrestricted diet, no differences were found in metabolic parameters.

If intermittent diets are therefore no less effective than others for weight loss, they cannot however be considered as “miracle diets”. Especially since other factors have to be taken into account, for example their impact on appetite and food balance.

Here again, the data from research are quite heterogeneous. We can nevertheless cite results that suggest that a continuous restrictive diet could be associated with a greater improvement in food balance , with the consumption of more varied meals and healthier habits, than intermittent diets.

Whether people on intermittent diets “overcompensate” by eating more during the times when they are allowed to do so is still unclear.

And finally, it must be emphasized that long-term adherence to diets , whether intermittent or not, is often low. In several studies, we observe that participants give up the diet along the way, with a risk of regaining the lost pounds. Promoting a balanced diet with medical support, also emphasizing regular meal times and physical activity remains an effective approach for many individuals.

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