Intermittent fasting is a dietary pattern that involves alternating periods of eating and fasting.

This modality of eating has been shown to have a wide range of health benefits that are explored below.

The most common form of intermittent fasting is the 16:8 method, where individuals fast for 16 hours and eat during an 8-hour window. Alternatively, in the 5:2 diet, one eats normally for 5 days a week and fasts for 24 hours, for 2 non-consecutive days.

Why does IF work?

1. One of the key mechanisms behind the benefits of intermittent fasting is the process of autophagy. Autophagy is the body's method of cleaning out damaged cells and recycling their components. It is activated during periods of fasting. This process has been linked to a reduction in the risk of chronic diseases such as cancer, cardiac diseases, Alzheimer's, and Parkinson's disease.

2. IF has also been shown to improve insulin sensitivity and glucose metabolism, which can help to prevent Type 2 diabetes.

3. A third mechanism seen in weight loss studies has been related to the fact that IF decreases the level of obesity-associated hormones and reduces appetite.

4. Intermittent fasting has also been found to have anti-inflammatory effects and may be beneficial for those with autoimmune conditions. In animal studies, it has been shown to improve the symptoms of multiple sclerosis and rheumatoid arthritis.

Weight loss and IF

The magnitude of weight loss in IF can vary depending on several factors such as the specific type of intermittent fasting being used, the individual's starting weight, overall diet and calorie intake, and exercise habits.

Studies have found that individuals who followed an IF diet lost an average of three to eight per cent of their body weight over 3 to 24 weeks.

It is important to note that weight loss may not be the primary goal for everyone who chooses to practice intermittent fasting and the benefits of this dietary pattern extend beyond it. Additionally, weight loss achieved with intermittent fasting tends to be more gradual than with other diets.

What is the effect of IF on the heart?

In most studies, IF has been associated with a modest and beneficial decrease in lipids and blood pressure and an improvement in endothelial function, a measure of the health of blood vessels.

The LDL-cholesterol level (the "bad" cholesterol) has shown mixed results. In most IF studies it has come down but in a few others, IF has caused an LDL increase and HDL decrease (the “good” cholesterol), especially in postmenopausal women. The significance of this finding is unclear at this point.

How about IF and the brain?

Intermittent fasting has been studied for its potential effects on cognitive health and dementia. Several animal studies have found that intermittent fasting can protect against cognitive decline and improve memory function.

One study found that intermittent fasting increased the production of a protein called brain-derived neurotrophic factor (BDNF), which is important for the growth and survival of neurons in the brain. Another study found that IF improved memory function in rats by increasing the number of new neurons in the hippocampus, a region of the brain that is important for memory.

In human studies, research suggests that intermittent fasting may have beneficial effects on cognitive health in older adults.

A study of adults aged 55 to 70 found that intermittent fasting improved memory, attention and processing speed.

A study published last week showed that vigorous exercise for six minutes or more increases the level of BDNF, potentially also helping to prevent dementia and overall cognitive decline.

Effect of IF on longevity

In animal studies, intermittent fasting has been shown to have a positive effect on longevity. In fact, studies in mice and rats have found that IF can increase life span by as much as 30 to 40 per cent! This is thought to be due to the above mechanisms – activation of autophagy, improved body hormones profile, and the anti-inflammation. However, it is important to note that the results from animal studies may not directly translate to humans. Studies in humans are needed to confirm these findings.

There is also evidence that caloric restriction, which is similar in nature to intermittent fasting, has been associated with an increase in life span in certain animal models, yet the results are not conclusive for humans.

In addition, it helps to remember that there are other factors that contribute to longevity, such as overall diet quality, exercise habits, genetics, and lifestyle choices (no smoking or excess alcohol, good sleep, low stress, and positive social connections).

How about combining IF and exercise?

Combining exercise with intermittent fasting can have a synergistic effect on overall health and fitness.

One study found that combining intermittent fasting with resistance training led to greater muscle gain compared with resistance training alone.

Another study found that combining IF with aerobic exercise led to greater weight loss and improved cardiovascular health markers compared with aerobic exercise alone.

IF and exercise can also work together to exponentially improve insulin sensitivity and glucose metabolism. A study found that combining intermittent fasting with "high-intensity interval training" (HIIT – more on that in next week's column) could significantly improve these two important metabolic markers.

To note: the above combination may not be suitable for everyone, particularly for those who are new to exercise or have a medical condition that limits their ability to exercise and/or fast.

How long can people adhere to an IF diet?

It is difficult to determine an exact percentage of people who can sustain intermittent fasting for a long time, as this can depend on a variety of physical and psychological factors.

Some studies have found that adherence to IF can be seen in as high as 80 per cent of participants at six months.

Intermittent fasting limitations

Aside from reaching a “floor” of three to eight per cent of weight loss with no additional significant decline, it's critical to note that not everyone may find intermittent fasting to be a sustainable long-term dietary choice. Some people may find it too restrictive or difficult to apply regularly, especially if they have a history of disordered eating or struggle with food cravings.

Some people may not find it practical to incorporate intermittent fasting into their daily routines – for instance, persons who work variable shift jobs (some nights and then some days).

Lastly, and very importantly, intermittent fasting may not be suitable for everyone, particularly for women who are pregnant, breastfeeding, or trying to conceive, and people who are underweight or have a history of nutrient deficiencies. Also, diabetic, cardiac or cancer patients should not try IF before they consult with a healthcare professional.

Joseph Yammine is a consultant cardiologist at the Bermuda Hospitals Board. He is also the director of the outpatient multi-speciality clinics and director of the Cardiac Computed Tomography programme. Nisrine Atieh is a Boston-based paediatrician and an American-board certified obesity medicine specialist.

The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician.