While this trendy diet may help shed the kilos, it is not suitable for everyone.

Intermittent fasting has been a trend among people trying to lose weight. Variations of this diet have been promoted by celebrities, further boosting its popularity. But does intermittent fasting really work? Is it necessary to consult a professional before adopting this diet?

“Intermittent fasting, when practised using the principles of a healthy and balanced diet, can lead to weight loss,” said Ms Alexis Ng Wei Leng (below), Dietitian, Department of Dietetics, Sengkang General Hospital (SKH).

Dietitians at SKH, however, do not routinely recommend that patients adopt intermittent fasting, preferring instead to encourage regular, balanced meals with daily caloric reduction for weight loss.

“This means there is no skipping of meals. It is safer and more sustainable in the long run. But if patients strongly desire to try intermittent fasting, we guide them so that they can do so safely,” said Ms Ng.

What it entails

Typically, intermittent fasting involves periods of intentional restriction of calories (or “fasting”) interspersed with periods of ad libitum feeding (or “feeding window”), where caloric intake is not calculated.

There are a few regimens that are widely practised. The most common ones are the 16:8 or 20:4 diets, which are based on the number of hours that fasting and feeding occurs. For instance, in the 16:8 diet, individuals fast for 16 hours and eat during the remaining eight hours. While fasting, they should hydrate themselves with calorie-free fluids, such as water, unsweetened green tea, or black coffee.

“It can be difficult to maintain this diet effectively because after long hours of fasting, one gets hungry and may lose inhibition of what he or she eats, and ends up unknowingly eating more than what he or she normally would,” Ms Ng said.

Another method is alternateday fasting, where individuals fast for one day and eat normally the next day, repeating the pattern for the duration of the diet. On the day of fasting, they can consume up to 25 per cent of their caloric requirements.

The 5:2 diet is another popular method, where individuals fast for two days of the week — either on consecutive or non-consecutive days — and eat normally during the other five days. On the days they fast, they can consume a maximum of 500kcal per day.

“The alternate-day fasting and 5:2 methods require individuals to be well-versed in calorie counting,” said Ms Ng.

Apart from helping to shed kilos, some studies have shown that intermittent fasting improves blood test results, such as fasting glucose, cholesterol levels, and even blood pressure. Some body functions are also enhanced, including increased insulin sensitivity, improved immunity and cognitive ability, as well as better protective effect against neurodegenerative diseases and ageing.

“It is important to note that these benefits were seen in study participants who followed a welldesigned and safe intermittent fasting regime while being closely monitored by healthcare professionals. If done without proper guidance, intermittent fasting could potentially cause more harm than good, so it is always important to seek professional advice,” Ms Ng said.

When first adopting this new diet, some may experience mild side effects, such as giddiness, headache, nausea, vomiting, diarrhoea, inability to focus, and temporary sleep disturbances. More serious but rare consequences like dehydration, nutrient deficiencies, and muscle loss have been reported among the general population, too.

Intermittent fasting is not recommended in certain groups of people — those under 18 or above 75 years of age, pregnant women, breastfeeding mothers, and individuals with eating disorders, uncontrolled diabetes or dementia. The list is not exhaustive.

“Intermittent fasting has not been shown to be superior in weight loss effectiveness when compared against daily caloric reduction with regular, balance meals. Nevertheless, anyone who wishes to embark on intermittent fasting is advised to consult a physician or dietitian to evaluate his or her suitability. We can then provide an appropriate diet plan, and monitor him or her through regular follow-ups throughout the period,” said Ms Ng.

Read more: Intermittent fasting isn't for everyone. Find out who should avoid it.

Tips for intermittent fasting

While embarking on your intermittent fasting journey under close monitoring with your healthcare professional, here are some pointers for you:

1. Balance is key

• Maintain a balanced diet during fasting days and feeding windows.

• Include food from all food groups to prevent nutrient deficiencies, weakened immune system, and poor wound healing.

2. Quality, not quantity

• Do not eat excessively during non-fasting days and during feeding windows.

• Limit intake of food with high-fat and refined-sugar content.

• Choose healthier cooking options such as stir frying, steaming, baking and roasting.

3. Mindful eating

• Avoid snacking between meals.

• Take time to savour each bite and chew your food slowly instead of gobbling down your meal.

4. Stay hydrated

• Drink plenty of zero-calorie fluids during fasting and feeding windows to avoid dehydration and headache.

• Do not mistake thirst for hunger.

5. Keep your energy level in check

• Fasting may affect hormone levels, leading to increased irritability, anxiety and stress.

• Fasting may lead to lethargy, which is dangerous especially if driving or operating machinery.

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