Benefícios do jejum intermitente

https://www.publico.pt/2019/12/27/impar/noticia/lidar-stress-jejum-intermitente-apontam-investigadores-1898613

Citando:
"Apesar de todos os benefícios, os investigadores alertam para os efeitos secundários: durante o primeiro mês, “os indivíduos que optarem pelo jejum intermitente podem manifestar irritabilidade e capacidade reduzida de concentração durante os períodos de restrição alimentar”. Assim, aconselha-se a que a janela temporal do jejum seja progressivamente aumentada, ao longo de vários meses, até atingir entre 16 e 18 horas."

Jejuns diversos?

Vários tipos de jejum, com benefícios para a perda de peso ou para a saúde (apesar dos escassos estudos científicos):

Citando:
"No “método 16/8”, basta fazer a última refeição às 20 horas, por exemplo. No dia seguinte, salta-se o pequeno-almoço. Ou seja, é um jejum de 16 horas, restando oito para a ingestão alimentar. Segundo a especialista, esta é a forma mais simples de seguir esta tendência.

Depois, tem o “método eat-stop-eat”, que é um jejum de 24 horas feito, no máximo, duas vezes por semana. Neste caso, pode, por exemplo, fazer do jantar a última refeição do dia. No dia seguinte, não pode comer nada até chegar novamente à hora de jantar.

E ainda há uma terceira forma: o “método 5:2”. Neste método só pode ingerir entre 500 a 600 calorias em dois dias não consecutivos da semana."

Fonte:

https://nit.pt/fit/alimentacao-saudavel/os-perigos-do-jejum-intermitente

Exercício físico em jejum melhor para perder peso?

Com as devidas ressalvas (ver citação) o exercício parece ser mais benéfico (para perder peso) é o realizado de estômago vazio:

Why exercise might be more beneficial on an empty stomach

Citação:

"The scientists took blood samples after fasting and the high carb breakfast and then after exercise. They also took adipose (fat) tissue samples immediately before and one hour after the walking exercise.

They discovered that the expression of two genes (PDK4 and HSL) significantly increased when the men fasted – but decreased when the men ate a high-calorie breakfast before they exercised. The increase in these genes suggested that fat was used to fuel the exercise, instead of the food consumed at breakfast.

Dylan Thompson, corresponding author of the study explained that this fat tissue often faces competing challenges. After consuming food it is busy responding to the meal and "and a bout of exercise at this time will not stimulate the same [beneficial] changes in adipose tissue. This means that exercise in a fasted state might provoke more favorable changes in adipose tissue, and this could be beneficial for health in the long term."

Although the study supports previous research, it is worthwhile noting the study sample was small and only looked at overweight men."

Intermitent fasting - o que é?

http://www.bbc.com/news/magazine-25498742 e...

O que é (citação):
"During each five-day fasting cycle, when I ate about a quarter the average person's diet, I lost between 2kg and 4kg (4.4-8.8lbs) but before the next cycle came round, 25 days of eating normally had returned me almost to my original weight.
But not all consequences of the diet faded so quickly."

http://www.bbc.com/news/magazine-25549805 (os efeitos: redução de IGF-1 associada ao crescimento de certos cancros e aparecimento de células regeneradoras, embrionárias - Stem Cell like).

Citando:
""You had a dramatic drop in IGF-1, close to 60% and then once you re-fed it went up, but was still down 20%," Longo told me.

Such a reduction could make a significant difference to an individual's likelihood of developing certain cancers, he says. A study of a small population of people in Ecuador, who have much lower levels of IGF-1, because they lack a growth hormone receptor, showed that they rarely develop cancer and other age-related conditions.

My blood tests also revealed that the major inhibitor of IGF-1, which is called IGFBP-1, was significantly up during the fasting period. Even when I resumed a normal diet, the IGFBP-1 level was elevated compared with my baseline. It is, according to Longo, a sign that my body switched into a mode that was much more conducive to healthy ageing.

Data from other participants in the study is still being analysed, but if they also show lower levels of IGF-1 and higher levels of IGFBP-1, it could help scientists develop an intermittent fasting regime that allows people to eat a normal diet for the vast majority of the time, and still slow down the ageing process.

One idea being explored by Longo is that a five-day intervention every 60 days may be enough to trigger positive changes in the body.

"This is exactly what we have in mind to allow people, for let's say 55 every 60 days, to decide what they are going to eat with the help of a good doctor, and diet in the five days. They may not think it is the greatest food they have ever eaten, but it's a lot easier, let's say, than complete fasting and it's a lot safer than complete fasting and it may be more effective than complete fasting."

The very small meals I was given during the five-day fast were far from gourmet cooking, but I was glad to have something to eat. There are advocates of calorie restriction who promote complete fasting.

My blood tests also detected a significant rise in a type of cell, which may play a role in the regeneration of tissues and organs."

Passar fome regenera Pâncreas (ajudando na diabetes Tipo 2)

Parecido com o livro sobre a reversão da diabetes tipo 2, há estudos que analisam o efeito da redução calórica (jejum) no pâncreas, parecendo que ajuda à sua regeneração e normalização dos níveis de açúcar no sangue:
http://www.bbc.com/news/health-39070183

Citando:
"Experts said the findings were "potentially very exciting" as they could become a new treatment for the disease.

People are advised not to try this without medical advice.

In the experiments, mice were put on a modified form of the "fasting-mimicking diet".

It is like the human form of the diet when people spend five days on a low calorie, low protein, low carbohydrate but high unsaturated-fat diet.

It resembles a vegan diet with nuts and soups, but with around 800 to 1,100 calories a day.

Then they have 25 days eating what they want - so overall it mimics periods of feast and famine.

Previous research has suggested it can slow the pace of ageing."

O estudo:
(published in the journal Cell)
http://www.cell.com/cell/fulltext/S0092-8674(17)30130-7

Os benefícios (e os perigos) de correr em jejum

http://www.correrporprazer.com/2015/06/correr-em-jejum/


Citando:
"A ideia de quem procura os treinos cardiovasculares (corridas ou caminhadas) em jejum é aproveitar o período em que as reservas de açúcar estão baixas para estimular a queima de gordura mais cedo no treino. “A questão é que o nosso cérebro consome preferencialmente açúcar e, na ausência deste, vamos obrigar o nosso corpo a produzir corpos cetónicos. Prolongando este quadro podemos causar cetose, elevando a acidez do sangue”, defende o ‘personal trainer’ e professor de capoeira António Braz, lembrando que a acidose prolongada pode ter efeitos nefastos.
Henrique Jones, ex-médico da seleção portuguesa de futebol, considera que uma refeição ligeira uma hora antes do exercício “é fundamental para preencher as reservas energéticas que permitem alimentar os músculos”."