When it comes to shedding pounds, numerous dubious suggestions pop up, including trendy diets like the carnivore diet and GOLO diet, as well as juice cleanses, vitamin injections, and a range of weight-loss products being promoted online, often lacking the promised benefits.

In contrast, established diets like the DASH diet and the Mediterranean diet, along with well-researched advice to cut back on sugar and salt, reduce calorie intake, and increase physical activity, are often recommended.

In between these extremes lies intermittent fasting, which has gained traction and grown popular among healthcare professionals and celebrities alike, including Jennifer Aniston, Chris Pratt, Kourtney Kardashian, and Jimmy Kimmel, as reported by People magazine.

However, it’s essential to understand that while intermittent fasting has benefited some individuals, it may not be suitable for everyone. Here’s a look at the advantages and disadvantages of this approach.

What is fasting?

Fasting involves refraining from eating or drinking for a specific period, although water and calorie-free beverages like tea or black coffee are usually allowed. According to Dr. Jesse Bracamonte, a family medicine physician at Mayo Clinic, the critical aspect of fasting is more about “when” you eat rather than “what” you eat.

Fasting can range from skipping a single meal to going without food while consuming only limited liquids for days. The duration typically depends on one’s motivations behind fasting.

Fasting is practiced in various religions like Judaism, Islam, and Christianity. For example, members of the Church of Jesus Christ of Latter-day Saints regularly fast for two meals in one day each month, while many Christians refrain from food intermittently during Lent to honor the 40 days Jesus fasted as described in the Bible.

Besides religious observances, doctors often request patients to fast for 6 to 12 hours before procedures, such as surgery or colonoscopies.

People commonly pursue intermittent fasting for weight loss or health benefits, leading to variations in duration. One popular intermittent fasting approach suggests fasting for a complete 24 hours once or twice each week, according to Bracamonte. There’s also the “5:2” method, where individuals eat normally for five days and limit their intake to 500-600 calories for the remaining two days. The “16:8 method,” also known as the Leangains diet, recommends a daily fasting period of 16 hours, allowing all meals within an 8-hour window.

Is fasting beneficial for you?

Participating in any of these intermittent fasting methods can yield benefits, provided certain factors are taken into account. A study published in the New England Journal of Medicine highlights various benefits associated with intermittent fasting, such as better blood pressure and resting heart rate, improved metabolic health, enhanced cognitive function, and increased fat burning. Other studies have reported similar findings.

These benefits occur, in part, because, according to Mark Mattson, a neuroscientist at Johns Hopkins Medicine who has researched intermittent fasting for 25 years, the body and brain cells respond positively to intermittent fasting, enhancing their functionality and resilience against stress and disease. He mentions that one way the body assists in managing a healthy weight is by depleting sugar reserves and turning to fat for energy after fasting for several hours, a concept he refers to as “metabolic switching.”

It’s important to note that weight loss during intermittent fasting primarily occurs due to a reduced calorie intake, as stated by Duane Mellor, a registered dietitian and evidence-based medicine and nutrition lead at Aston Medical School in England.

Additionally, there is some evidence suggesting that intermittent fasting might aid in improving insulin resistance through hormonal changes that arise during food deprivation. Bracamonte also points out that fasting could bolster cellular repair, helping the body recover from illnesses and injuries and rejuvenating aging tissues.

How many times a week can you fast?

Despite its positive aspects, intermittent fasting isn’t suitable for everyone. Some individuals may experience fatigue, headaches, or irritability during fasting, though these side effects usually diminish as the body adjusts to changes in calorie intake.

Mellor notes that some people struggle to eat regularly on their non-fasting days, which may lead to binge-like behaviors, although research in this area remains inconclusive. There’s also a risk of missing out on vital nutrients if fasting is practiced excessively or too frequently.

Mattson highlights that existing randomized controlled trials have mainly involved adult men and women and have not indicated any adverse effects of intermittent fasting in these populations. However, caution is advised for children, pregnant women, and frail elderly individuals, and it’s recommended they consult their doctor before attempting fasting.

For those interested in intermittent fasting, Bracamonte recommends starting slowly, listening to your body, and monitoring any negative feelings. It’s also wise to plan meals in advance to ensure your body gets the necessary nutrients.