Intermittent Fasting: Is it for you?
What is intermittent fasting?
Intermittent fasting is a dietary practice that alternates between eating and minimal to no food or calorie intake. There are various fasting practices, some of which have strong religious and cultural significance, such as Ramadan fasting in Islam and fasting in Christianity.
Some intermittent fasting regimes:
*Prolonged fasting: Typically involves fasting for more than 24-36 hours
Eat-stop-Eat: Involves minimal to no food intake for 24 hours scattered within a normal eating schedule
5:2 fasting: Consists of consuming a low to no amount of calories for two days per week
Time restricted eating (e.g. 16/8; 18/6): Allows you to consume food normally but only within a predetermined eating window each day.
*One meal a day (OMAD): as the name suggests, you eat only one meal a day.
*Alternate day fasting: alternate between eating and fasting, so there’s no 2 consecutive eating or fasting days.
§Warrior fasting: a type of time-restricted eating, with 20 hours of fasting followed by a 4-hour eating window
*Do not attempt without medical supervision.
§Generally not recommended
Why intermittent fast? - Any concerns?
Religious and cultural practices
Fasting practices have deep roots in religious, spiritual, and cultural traditions. We respect these traditions and do not discourage fasting for religious or cultural reasons.
However, if you have any health problems (e.g., nutritional deficiencies, disordered eating, low blood pressure, low blood sugar, diabetes, etc.) or experience discomfort (e.g., fatigue, nausea, etc.), or if you are seeking alternatives to appetite-depressing agents (e.g., recreational drugs, cigarettes, etc.), it's important to discuss your fasting practice and health concerns with a doctor or dietitian for proper care management.
Weight loss
Intermittent fasting, particularly time-restricted eating, has gained popularity as a new dietary practice for weight loss. The appeal lies in its simplicity—no major changes to your regular diet, just a specific eating window.
What do the science say? Multiple health reviews suggest that both intermittent fasting and time-restricted eating can be effective in the short-term weight loss (8 weeks to half a year), but not superior to other dietary approaches (1-5). The effectiveness of any diet depends on the level of calorie restriction and the adherence to it. If a dietary approach isn't practical for your lifestyle, it may result in yo-yo dieting, even if it has scientific backing.
Risks. Binge eating is more likely to occur after a fasting period, as your body is under stress during extended fasts, and your mind becomes more alert to food. This is particularly common in people with a history of binge eating and other eating disorders, which could worsen with intermittent fasting. Approximately 29% of people seeking weight loss have a history of binge eating (6), indicating a similar percentage of those attempting intermittent fasting for weight loss may experience repetitive binge eating.
Improving health markers
What do the science say? While most people view intermittent fasting as a weight loss tool, it shows promise in improving health markers, especially metabolic health. Evidence suggests that intermittent fasting may improve blood lipid and cholesterol profiles, blood pressure, and reduce low-grade inflammation (4-5,7). Some early studies suggest it might stabilise blood glucose (8-9); however, its use for diabetes management remains inconclusive.
Risks. Intermittent fasting research has identified some less desirable effects, including lethargy, fatigue, insomnia, irritability, increased hunger, bad breath, headaches, constipation, and nausea, which could cause long-term concerns.
Should I start intermittent fasting?
Definitely not recommended:
*Children and adolescent under 18 years of age
*Elderly over 65 years of age
People with a BMI below the healthy range (<18.5kg/m2 for age of 18-65; <23kg/m2 for age of 65 and over)
Individuals with varying degrees of malnutrition
Women with PCOS, menstrual dysregulation and other infertility problems
During pregnancy or during breastfeeding
People with clinical conditions require nutrition supports (e.g. respiratory diseases, neuromuscular diseases, bone fracture, post operation recovery, active cancer treatment, cancer recovery, infection, burns)
People with active eating disorders or disordered eating
People and athletes recovery from injuries
Athletes with high-intensity training programs
*exception for religious and cultural practices
Trial with guidance of a dietitian and GP:
People who have recovered from previous eating disorders, or with history of binge eating or emotional eating
women looking to conceive but otherwise healthy
people with all types of diabetes (type1, type 2, gestational and steroid-induced), especially managed with medication and insulin
people with other diagnosed health problems (e.g. high blood lipid/dyslipidaemia, kidney diseases, obesity, heart diseases)
people with weight and body concerns seeking a sustainable change.
people with digestive issues (e.g. constipation, indigestion, bloating, IBS etc.)
Takeaway messages
Intermittent fasting may work for some people but not for everyone (refer to the suitability list above). It is crucial to choose a healthy eating style that suits you rather than blindly following health trends.
Intermittent fasting comes in various regimes and may help with weight loss and reduce metabolic health risks.
If you experience any side effects from intermittent fasting, stop it immediately or consult an accredieted dietitian (like us) or GP.
References
Welton S, Minty Rm O’Driscoll T, Willms H, Poirier D, Madden S, Kelly L. Intermittent fasting and weight loss. Can Fam Phys.2020;66(2):117-125
Freire R. Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets. Nutrition;2020; 69:110549
Rynders CA, Thomas EA, Zaman A, Pan Z, Catenacci VA, Melanson EL. Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. Nutr.2019;11(10):2442
Tinsley GM, La Bounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr. Rev. 2015;73(10):661-674
Santos HO, Macedo RCO. Impact of intermittent fasting on the lips profile: Assessment associated with diet and weight loss. Clin Nutr. ESPEN.2018;24:14-21
McKuen-Wurst C, Ruggieri M, Allison KC. Disordered eating and obesity: associations between binge-eating disorder, night-eating syndrome, and weight-related comorbidities. Ann N Y Acad Sci.2018;1411(1):96-105
Wang X, Yang Q, Liao Q, Li M, Zhang P, Santos HO, Kord-Varkaneh H, Abshirini M. Effects of intermittent fasting diets on plasma concentrations of inflammatory biomarkers: a systematic review and meta-analysis of randomised controlled trials.Nutrition.2020;79-80:110974
Arnason TG, Bowen MW, Mansell KD. Effects of intermittent fasting on health markers in this wth type 2 diabetes: A pilot study. World J Diab. 2017;8(4):154-164
Faris MAI, Bahrami H, BaHammam A, Kalaji Z, Madhour M, Hassanein M. A systematic review, meta-analysis and meta-regression of the impact of diurnal intermittent fasting during Ramadan on glucometabolic markers in healthy subjects. Diab. Res. Clin. Prac.2020;165:108226
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