Review of intermittent fasting research suggests broad health benefits (2024)

Review of intermittent fasting research suggests broad health benefits (2)

Review of intermittent fasting research suggests broad health benefits

Review of intermittent fasting research suggests broad health benefits (4)

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A new analysis of current intermittent fasting research suggests the dietary strategy could soon be incorporated as standard medical health and diet advice

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Some of the health benefits of intermittent fasting cited in the new review article

John Hopkins University

A newly published review article in The New England Journal Of Medicine has examined an array of current research on intermittent fasting, from animal studies to human clinical trials. The review clarifies different fasting regimes while also outlining a variety of health benefits the eating strategies can confer in humans.

Although intermittent fasting is currently a bit of a dietary trend, scientists have been investigating the effects of irregular caloric intakes in animals for several decades. Mark Mattson, an author on the new review and neuroscientist from Johns Hopkins University, explains one of the key processes triggered by intermittent fasting is called metabolic switching.

When an organism is starved of food it shifts how it produces energy, switching from readily accessible glucose in consumed food to a process called ketogenesis, whereby molecules called ketone bodies are produced though the conversion of fat stores. This energy production shift is dubbed metabolic switching, and Mattson’s review article suggests frequent shifts between the two metabolic states can result in an array of health benefits.

“Periodic flipping of the metabolic switch not only provides the ketones that are necessary to fuel cells during the fasting period but also elicits highly orchestrated systemic and cellular responses that carry over into the fed state to bolster mental and physical performance, as well as disease resistance,” write Mattson and co-author Rafael de Cabo.

Review of intermittent fasting research suggests broad health benefits (6)

John Hopkins University

The review breaks intermittent fasting into two general categories: alternate day fasting and time-restricted feeding. Alternate day fasting involves significant caloric restriction on one day or more each week – the modern 5:2 eating regime is a variation on alternate day fasting. Time restricted feeding, on the other hand, involves fasting for a period within the 24-hour cycle – this category would include the common 16:8 regime, which restricts all caloric intake to a period of no more than eight hours in a given 24-hour period.

What is the ideal intermittent fasting regime? That is still unclear. The article notes that ketone bodies have been found to begin rising in humans within eight to 12 hours of fasting, suggesting time-restricted feeding methods could be effective in harnessing the health benefits of metabolic switching. So 16 hours of fasting every day may be an easy way to implement a form of intermittent fasting. A recent study has even suggested dropping that fasting period down to 14 hours a day confers health benefits.

Mattson and de Cabo suggest in the review article that physicians incorporate intermittent fasting dietary strategies into treatment regimes for patients at risk of everything from dementia to cardiovascular disease. And, understanding the challenges patients have in maintaining these kinds of dietary interventions, the article describes gradually increasing fasting periods over a number of months as the most effective way to deploy such dietary changes.

So, for example, the article suggests for the first month’s intervention a patient only drop to either 10-hour feeding a day for five days a week, or 1,000 calories in total one day per week. Gradually over several months this intervention would transition, so by month four the patient reaches either a complete time restricted feeding regime eating only six hours a day every day, or a 5:2 regime of no more than 500 calories for two days every week.

“Patients should be advised that feeling hungry and irritable is common initially and usually passes after two weeks to a month as the body and brain become accustomed to the new habit,” Mattson explains.

The review article does stress there is much still to be explored in terms of the long-term effects of intermittent fasting and in understanding the biological mechanisms that may be at play. However, it does seem increasingly clear that our current culture of always available food, and near constant snacking, is not necessarily the best way to feed. And, while there is still more research needed before broad conclusions and recommendations can be made, Mattson is confident we are close to a point where intermittent fasting regimes could be incorporated into popular health advice.

“We are at a transition point where we could soon consider adding information about intermittent fasting to medical school curricula alongside standard advice about healthy diets and exercise,” Mattson concludes.

The new review article was published in The New England Journal of Medicine.

Source: Johns Hopkins Medicine

Review of intermittent fasting research suggests broad health benefits (2024)

FAQs

Are there any evidence based health benefits of intermittent fasting? ›

These include a longer life, a leaner body and a sharper mind. “Many things happen during intermittent fasting that can protect organs against chronic diseases like type 2 diabetes, heart disease, age-related neurodegenerative disorders, even inflammatory bowel disease and many cancers,” he says.

What is the medical review of intermittent fasting? ›

A systematic review of 40 studies found that intermittent fasting was effective for weight loss, with a typical loss of 7-11 pounds over 10 weeks. [2] There was much variability in the studies, ranging in size from 4 to 334 subjects, and followed from 2 to 104 weeks.

Why do doctors recommend intermittent fasting? ›

Losing weight and being physically active help lower your risk of obesity-related diseases, such as diabetes, sleep apnea and some types of cancer. For these diseases, intermittent fasting seems to be about as beneficial as any other type of diet that reduces overall calories.

Why is 16 hours the magic number for fasting? ›

While both 12-hour and 16-hour fasting can promote fat burning, it's possible that a 16-hour fast may be more effective. This is because the longer fasting period may lead to a greater depletion of glycogen stores, which can trigger higher levels of fat burning.

Is there any real science behind intermittent fasting? ›

Hundreds of animal studies and scores of human clinical trials have shown that intermittent fasting can lead to improvements in health conditions such as obesity, diabetes, cardiovascular disease, cancers and neurological disorders. The evidence is less clear for lifespan effects.

What is the current evidence on intermittent fasting? ›

In addition, a September 2020 randomized clinical trial — considered the gold standard of research — that looked at 116 people found no significant difference in weight loss between people who restricted eating from 8 p.m. and noon the next day and those who did not.

What does Dr Fung say about intermittent fasting? ›

Fung says the most common fasting strategy is 16 hours of fasting and eating within an eight-hour time period. "So you might eat for example from 11 a.m. to 7 p.m. or you might do it early, say 9 a.m. until 4 p.m. There's various ways to do it, but that's one of the more popular schedules," he said.

What is the most beneficial intermittent fasting method? ›

Many people consider the 16/8 method the simplest and most sustainable form of IF — you might want to try this practice first. If you find it easy and feel good during the fast, then maybe try moving on to more advanced fasting methods. Another approach is to fast whenever it's convenient.

What are the cons of intermittent fasting? ›

Symptoms within the first month of adopting the intermittent fasting diet
SymptomsMildSevere
Constipation29 (19.7%)9 (6.1%)
Dizziness41 (27.9%)16 (10.9%)
Vomiting16 (10.9%)4 (2.7%)
Dehydration27 (18.4%)5 (3.4%)
9 more rows
Feb 7, 2023

Is it better to skip breakfast or dinner in intermittent fasting? ›

With intermittent fasting, breakfast is not only optional, it's discouraged. The most common method is a 16-hour overnight fast, followed by an 8-hour eating window. Yet, nutrition professionals have long suggested that breakfast is critical.

Does coffee break a fast? ›

Can You Have Coffee When Fasting? The general consensus is that, yes, drinking black coffee without added sugar or cream won't affect your fast in any significant way. It's similar to any very low-calorie drink.

What is the best intermittent fasting window to lose belly fat? ›

A 2023 review of research found that the 16/8 method and 16/8 combined with restricting calories were effective strategies for weight control in adults with overweight or obesity. An eating window starting before noon led to greater weight loss than one that began after noon.

Does sleep count as fasting? ›

This is because the fasting window is relatively small, much of the fasting occurs during sleep, and the person can consume the same number of calories each day. The easiest way to do the 12-hour fast is to include the period of sleep in the fasting window.

Is it okay to fast 16 hours everyday? ›

For example, studies have found that people who regularly fast more than 16 or 18 hours a day have a higher risk of gallstones. They're also more likely to need surgery to remove the gallbladder. Eating for 12 hours and then fasting for 12 hours is likely safe for most people, Longo explains.

Is there any evidence that fasting is good for you? ›

Evidence suggests that some forms of fasting may benefit your gut microbiome. Studies involving men who fasted for 16 hours a day found that the participants had more beneficial bacteria in their gut microbiomes.

What are the arguments against intermittent fasting? ›

However, if you take fasting to the extreme, intermittent fasting may risk disordered eating, rebound eating that causes weight gain, and sleep disturbances. What's more, there isn't enough evidence showing whether intermittent fasting is a sustainable eating pattern.

Does intermittent fasting have health benefits Harvard? ›

Intermittent fasting can help weight loss

Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don't use it all, we store it in our fat cells as, well, fat.

Is 16 hours fasting enough for autophagy? ›

It provides benefits, including reduced disease risks, better weight and weight-related health management, and promotes a healthier and longer life. While studies are ongoing, research suggests you'd have to fast for a minimum of 12 to 16 hours to induce autophagy.

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