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Intermittent Fasting: Human study shows why it can lead to weight loss

U Contrary to some other trends in fad diets, growing evidence indicates that there is some temporary fasting. Studies on animals and humans show some effects on weight loss, and now a human study gives us a much better idea of ​​how the diet works.

An article published in Obesity on Wednesday focused on limited-duration feeding, a form of intermittent fasting, where people consume all their meals within a certain period of time. Normally, explanations for the success of intermittent fasting depend on calories ̵

1; either that intermittent fasting ones eat less of it or even burn it at a higher rate. But this paper suggests that the reason the diet works may not have anything to do with calories.

Instead, reduced eating habits tended to reduce appetite over time as people overcrowded all their meals for a period of six hours between 8:00 am and 2:00 pm.

The difference between appetite and calorie burning may seem unimportant, but it's a significant change from what scientists suspected in intermittent fasting – at least based on some animal models, says lead author, Courtney Peterson, Ph.D., associate professor for Nutrition Science at the University of Alabama.

"Some studies on rodents showed that feeding them for a limited period of time helped rodents burn more calories," she says Inverse. "Unfortunately, we have found that feeding for a limited period of time does not help people burn more calories (as is the case with rodents)."

"However, we found three useful things," she continues , In particular, the results of her team point to temporary feeding effects on hunger and fat burning.

How Temporary Feeding Affects Hunger

The strongest evidence from Peterson's study suggests that feeding for a limited period affects the way the body handles hunger. Study participants who ate all meals within this six-hour window before 14:00. reported a more even sense of hunger, an increased sense of fullness, and a reduced desire to eat.

  Benefits of Fasting
Temporary feeding, a form of intermittent fasting, appears to affect human appetite but not calorie burning.

When Peterson and her team examined their participants' blood samples, they have a sense of where these feelings might come from.

During fasting, they observed a significant decrease in the amount of ghrelin produced by their participants. Ghrelin is the hormone that is normally produced when the stomach is empty, and it essentially tells the body that it's time to replenish itself. This is one of the reasons why it is known as a "hunger hormone".

In this new article, the team claims in particular that not only is this time-limited feeding itself responsible for these hormonal changes. They argue that the actual time of the meal could be partly responsible for the suppression of the appetite. When people eat earlier in the day, they tend to make sure they eat during the "biological day" – the part of the circadian 24-hour cycles that regulates wakefulness, calorie burning, or hormone release.

The consumption of meals during the biological night has been shown to affect weight gain in mice and night shift workers. So the idea is that timing the feeding window to the biological day may be one reason that time-limited feeding is an "effective appetite reduction and weight loss strategy".

How Time-Feeding Affects Fat Burning [19659008] Peterson and her team also found that early eating changed the way the subjects burned fuel. First and foremost, they found that fat burning increased during the day, which makes sense given the fact that people stopped eating at 2:00 in this study.

"We believe that prolonged daily fasting gives the bodies more time to immerse themselves in their fat reserves and burn fat every day," says Peterson. "The body can normally burn maximum fat if people fast at least 12 to 24 hours at a time."

The time-limited eating plan also increased their subjects' "metabolic flexibility." Metabolism Flexibility is how well the body switches between burning different types of fuel sources, such as carbohydrates, proteins, or fats. that increasing flexibility can help combat obesity or reduce the risk of Type II diabetes.

Peterson's promise, however, is that we can not associate these additional metabolic changes too much with long-term changes Their study focused more on the effects on appetite and calorie burning, but this finding will be discussed later.

Related video: Circadian rhythms affect sleep and hormone release and hunger.

Applying this finding Eating on Diets

Peterson's trial seems to be good news for students of limited-time feeding. However, she is curious that the six-hour food window used in her experiment is a very extreme version of an already difficult diet. In general, she does not recommend eating all meals over a six-hour period.

"In the real world, however, we recommend an 8-10 hour meal period of 5 to 6 days a week. Both my and Dr. Krista Varady's research suggests that this is a more realistic goal. "

Nevertheless, there is some evidence that time-limited food has no calorie-burning effects that can be counterbalanced elsewhere.


Purpose: Early eating a day to adapt to the daily rhythm of the metabolism increases weight loss. However, it is not known if these benefits are due to increased energy expenditure or reduced food intake. Therefore, this study conducted the first randomized study to determine how the time of the meal affects the 24-hour energy metabolism when food intake and meal frequency are matched) (food 8am to 2pm) and a control plan (food from 8 to 20 o'clock) for 4 days. On the fourth day, 24-hour energy consumption and substrate oxidation were measured by indirect full-room calorimetry in conjunction with appetite and metabolic hormones.

Results: eTRF did not affect 24-hour energy consumption (Δ = 10 ± 16 kcal / d, P = 0.55). Despite the prolonged daily fasting (intermittent fasting), eTRF reduced the mean ghrelin level by 32 ± 10 pg / ml (P = 0.006), made the dog more uniform (P = 0.006) and increased the abundance (P =) 0.06-0, 10) and reduce the craving to eat (P = 0.08). eTRF also increased metabolic flexibility (P = 0.0006) and decreased the 24-hour non-protein respiratory quotient (Δ = -0.021 ± 0.010, P = 0.05).

Conclusions: Interventions at the time of the meal facilitate weight loss mainly by reducing appetite rather than by increasing energy expenditure. eTRF can also increase fat loss by increasing fat oxidation.

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