Some fasting diet methods do not impose any food restrictions during the periods you can eat. (Credit: Shutterstock)
Fasting has been advocated for many years for both medical and religious purposes. The fasting diet has gained attention in recent years after studies began to show its potential for weight loss. Some studies have shown intermittent fasting can be effective for short-term weight loss among people who are at an ideal weight, overweight and obese.
A 2021 review published by the Journal of the American Medical Association shows intermittent fasting might be associated with weight loss, reduced body weight, fat mass, total cholesterol, triglycerides and blood pressure in adults who are overweight or obese.
Fasting diet checklist
Fasting and shifting meal frequency have grown in popularity as diet methods. But before beginning your fast, here's an important checklist of considerations:
1. Get your doctor's approval
There are fasting diets with no food restrictions on the days you can eat. But you are still advised to stick to the recommended calorie intake – 2,500 calories for men and 2,000 calories for women per day. Then, on fasting days, you only drink water or no-calorie beverages like plain coffee or tea.
It's not a typical eating pattern, so more research and monitoring are needed to ensure its safety and effects on your body in the long term. There are questions as well if you get enough nutrients when you fast. So, don't try it without consulting a doctor who knows your medical history.
2. Look into pre-existing conditions
People with the following conditions are advised not to attempt a fasting diet on their own:
- Children under the age of 18
- Pregnant or breastfeeding women
- People with diabetes
- People with eating disorders
3. Ready your mind and body
The fasting diet is not only about making a lifestyle change – it can be hard on your body. Fasting can make you irritable or cranky if you are used to eating every few hours. Can you resist the hunger pangs for over 10 hours?
A diet review published in the Nutrition Source of Harvard T.H. Chan School of Public Health shows people tend to indulge or overeat after being deprived of food for hours or days. This shows that you also need to have discipline and self-control to make it work.
Popular fasting methods
Here's an overview of four popular fasting methods for weight loss to get a picture of what your body will go through during a fast.
Many who try fasting for the first time go for time-restricted fasting because it suits their body clocks. With this method, you only eat meals during a designated time.
One approach is the 16:8 intermittent fasting method, which suggests 16 hours of fasting, followed by eating within an 8-hour window in a day. As an example, you can fast between 8pm and 12 noon the next day. You can still have water or other no-calorie beverages during this period.
Alternating between days of fasting and "feasting" allows you to eat freely without any restrictions. On days of fasting, you're allowed to consume 25 per cent of your daily calorie needs – 450 calories for women and 550 calories for men.
Calorie count declines even when you have "feast" days because you go for extended periods without eating. (Credit: Shutterstock)
This requires five days without calorie restrictions and then fasting for two consecutive days per week. You can eat 450- or 550-calorie meals on those two days of fasting. The 5-2 method is one of the popular types of prolonged fasting.
A fasting-mimicking diet (FMD) is a calorie-restricted, low-carbohydrate, low-protein diet with high, good fats. You can do it for four to five days a month. You do not go without food, yet FMD "mimics" the conditions the body experiences when fasting.
A research article published in Cancer Discovery using mouse models utilised a fasting-mimicking diet in antitumour treatments. The results suggest that FMD may help improve metabolism and boost immunity in patients with cancer.
Fasting diet benefits
Weight loss is one of the most significant fasting diet benefits. According to Harvard University's School of Health, the typical weight loss in a fasting diet is 3 to 5 kg over 10 weeks, based on a systematic review of 40 studies. However, note that these studies had different variables, from the number of subjects to the type of fasting diet used.
Fasting has also shown promise in boosting body and brain health. Research published in Nutrients (2019) and the American Journal of Medicine (2020) suggest that intermittent fasting could reduce the risk of cardiovascular disease with an improvement in weight control, hypertension, dyslipidaemia (imbalance of lipids) and diabetes.
Other studies have suggested that fasting may have beneficial effects on ageing. Valter Longo, PhD, one of the leading researchers of the fast-mimicking diet, shares that the diet "reduces the risk factors and markers associated with ageing and diseases."
Fasting might help to improve the following:
- glucose control
- blood pressure
- cognitive performance
- metabolic function
Any diet should be paired with physical activity or exercise to maintain weight loss. (Credit: Getty Images)
The potential benefits will be lost if you overindulge on "feast" days. Fasting may help you manage your weight, but preventing disease requires other healthy lifestyle habits. You still need a good amount of exercise or physical activity. Avoid sugar-laden foods and instead eat healthy fats, lean proteins, fruits, vegetables and whole grains on feasting days.
If you choose to try the fasting diet, it is best to have medical and nutritional guidance from health professionals. Find the right health insurance with a medical protection plan that covers your needs. You may have health conditions that may be adversely affected by changes in eating patterns. Preparing well in advance is part of taking care of your physical, mental and financial wellbeing.
National Institute on Aging. 2018. Calorie Restriction and Fasting Diets: What Do We Know? [online] [Accessed on 5 July 2022]
Harvard T.H. Chan's The Nutrition Source. Diet Review: Intermittent Fasting for Weight Loss. [online] [Accessed on 5 July 2022]
John Hopkins Medicine. Intermittent Fasting: What is it, and how does it work? [online] [Accessed on 5 July 2022]
The New England Journal of Medicine. 2019. Effects of Intermittent Fasting on Health, Aging, and Disease. [online] [Accessed on 5 July 2022]
Clinical Nutrition Journal. 2020. Intermittent fasting 5:2 diet: What is the macronutrient and micronutrient intake and composition? [online] [Accessed on 5 July 2022]
Science Translational Medicine. 2017. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. [online] [Accessed on 5 July 2022]
Cancer Discovery. 2022. Fasting-Mimicking Diet Is Safe and Reshapes Metabolism and Antitumor Immunity in Patients with Cancer. [online] [Accessed on 5 July 2022]
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