Intermittent fasting or caloric restriction: What do scientific studies say? It seems that weight loss is similar. Explanations.
What is intermittent fasting, what is it?
The term “intermittent fast” covers very diverse practices, such as: diet 5: 2 (with two days of caloric restriction per week), fasting in alternating 1 day in 2 and the restricted food period, or TRF (time restricted feeding), which consists in restricting the time window where you eat during the day.
In the end, all these methods aim to reduce the amount of calories consumed, but without having to count them precisely with each meal. Intermittent fasting therefore appears to be easier to set up than a “classic” calorie restriction. But is it also effective in losing weight?
A study from the University of Illinois in Chicago, which compared the calorie restriction and a TRF fast on a full year, suggests that the two approaches are equal.
About 5 kg lost in one year
The study of the University of Illinois: Fast TRF 16/8 vs caloric restriction of 25 %
For this clinical trial, the researchers recruited 90 obese adults, which they separated into three groups:
- An “intermittent fasting” group which was to consume all its calories between noon and 8 pm (fast fast with the 16/8 method), without having to count its calories;
- A “caloric restriction” group which was to reduce its energy intake by 25 %;
- A control group.
On average, participants reduced their daily energy intake of 425 calories in the TRF group and 405 calories in the “Caloric restriction” group. During the first six months, Participants of the two intervention groups lost an average of 5 % of their weight.
| Steady fasting | Caloric restriction | |
|---|---|---|
| Protocol | Eat between 12 p.m. and 8 p.m. | Reduce its calorie intake by 25 % |
| Reduction of calorie intake per day | 425 calories | 405 calories |
| Weight lost on average at 6 months | -5 % | -5 % |
Comparison of results at 12 months
Then, the regimes were adjusted to maintain this weight loss in the following six months: participants who followed intermittent fasting extended their power window from 10 a.m. to 8 p.m., and those of the “caloric restriction” group were able to increase their intake, according to their weight, age and activity.
In the end, the two types of diets gave quite close results after 12 months: -4.6 kg in the “Intermittent fast” group and -5.4 kg in the caloric restriction group, a difference that the authors consider it as non -signifating. The waist tower and fat mass have also decreased in these two groups.
Our metabolism is more effective earlier in the day
On the other hand, there was no effect on glucose or insulin levels. For Dr. David Clayton, lecturer in physiology of exercise and nutrition at Nottingham Trent University, it would be linked to the food window chosen for intermittent fasting. Indeed, other works show that control of blood sugar is improved if the power window authorized in intermittent fasting is moved earlier in the day (for example 8h-6h).
“Research suggests that our metabolism is more effective earlier in the day,” he explains on the site The Conversation.
Similar results were observed in a Chinese study comparing intermittent fasting 16/8 and caloric restriction in 139 obese people: weight loss was not significantly different in the two groups.
Read: Better fast in the evening or in the morning to lose weight?
The importance of dietetic and psychological monitoring
However, Dr. Clayton notes the importance of participants’ psychological monitoring: “An important aspect of this study which makes it difficult to conclude that these interventions are sufficient to help people lose weight is the fact that participants from the two dietary intervention groups received a lot of advice during the study. »» Participants were advised on their diet and followed TCC (cognitive behavioral therapy) to reduce their food impulses. “It probably helped participants reduce the desire to eat foods rich in calories after finishing their fasting window. »»
We can therefore wonder if, without this support, participants could have lost weight with the same efficiency, because as Dr. Clayton points out: “Following a diet is difficult, whatever the method used. »»
Frequent questions about intermittent fasting
What are the benefits of intermittent fasting?
Beyond weight loss, intermittent fasting is beneficial to cardiovascular health and can help reduce blood pressure. It also protects against inflammation.
Read: the benefits of intermittent fasting
Is intermittent fasting effective in losing weight?
Yes, different scientific studies show that intermittent fasting allows weight loss. According to a meta-analysis published in 2022 in the review Nutrientsit would even be more effective than calorie restriction.
Can we drink during the fasting period?
Yes, water of course, tea, herbal teas, coffee (moderately), broth are all acceptable. Liquids can even help control hunger!
Can we play sports during a fast?
Twice yes: walking, cycling, gymnastics, swimming, yoga … are even recommended during a fast. The exercise makes it possible to strengthen elimination, to maintain muscle mass and also help to maintain itself (therefore not to think of hunger or to eat).
Are there contraindications to intermittent fasting?
Fasting is not recommended for children and adolescents (periods of growth) but also to women during pregnancy and breastfeeding. Because it modifies many metabolic parameters, fasting is absolutely contraindicated if you have the following diseases or disorders: renal failure, hepatic insufficiency, hypotension, hyperthyroidism, type 1 diabetes, denutrition, detachment of the retina, cardiac arrhythmia, unstable or serious coronavirus disease.
Retain
- A 12 -month study shows that intermittent fasting (method 16/8) is as effective that the caloric restriction continues to lose weight.
- Both methods lead to a loss of 5 % of body weight after six months.
- The choice between the two approaches can be made according to personal preferences and lifestyle.
