Intermittent fasting is one of the safest and most effective ways to lose weight. There are many different varieties, including the 5:2 and 16:8 diets, but according to a recent analysis conducted by the University of Illinois at Chicago, there is one approach that trumps the others in terms of efficacy and adherence.
Unlike the vegan diet or keto diet, intermittent fasting is a special kind of diet as it doesn't restrict what you can eat; it only specifies when you can take your meals. The two most popular versions are the 5:2 diet – with five regular eating days and two fasting days – and the 16:8 diet – where you fast every day for 16 hours and eat for eight – but there are probably hundreds of versions of these two, all being a variation on the theme.
In a recent analysis called "Cardiometabolic Benefits of Intermittent Fasting (opens in new tab)" (via ScienceDaily (opens in new tab)), published in the Annual Review of Nutrition in October 2021, researchers concluded that "all forms of fasting reviewed produced mild to moderate weight loss, 1%-8% from baseline weight."
The paper also notes that "results [from intermittent fasting diets] are similar to that of more traditional, calorie-restrictive diets", which might sound strange at first, but at the end of the day, the old saying "calorie is king" still stands. Any diet that restricts calorie intake will eventually result in weight loss, one way or another.
That said, intermittent fasting has more than one health benefit (if weight loss can be considered a health benefit). As the paper states, "Intermittent fasting regimens may also benefit health by decreasing blood pressure and insulin resistance, and in some cases, cholesterol and triglyceride levels are also lowered. Other health benefits, such as improved appetite regulation and positive changes in the gut microbiome, have also been demonstrated."
Both alternate-day fasting – feast day alternated with a fast day where 500 calories are consumed in one meal – and the 5:2 diet resulted in similar results, which surprised the researchers as 5:2 dieters fast much less frequently than alternate-day fasting participants.
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Intermittent fasting dos and don'ts
The study review also offers some practical tips on how to ease yourself into an intermittent fasting regime easier, as listed on ScienceDaily:
- Adjustment time – Side effects such as headaches, dizziness and constipation subside after one to two weeks of fasting. Increased water intake can help alleviate headaches caused by dehydration during this time.
- Exercise – Moderate to high-intensity endurance or resistance training during food abstention can be done, and some study participants reported having more energy on fast days. However, studies recommend those following alternate day fasting eat their fasting day meal after exercise.
- Diet during fasting – There are no specific recommendations for food consumption during intermittent fasting, but eating fruits, vegetables and whole grains can help boost fiber intake and help relieve constipation that sometimes accompanies fasting.
- Alcohol and caffeine – For those using an alternate day or 5:2 fasting plan, alcohol is not recommended on fast days as the limited calories should be used on healthy foods that provide nutrition.
The review also suggests that intermittent fasting might not be ideal for certain types of people, including people who are pregnant or lactating, children under 12, those with a history of disordered eating, those with a body mass index, or BMI, less than 18.5, shift workers and finally, people who need to take medication with food at controlled times.
In conclusion, 5:2 might be your best option to start your intermittent fasting journey. Once you have begun seeing some weight loss results and experienced some of the diet's health benefits, you can consider trying alternate-day fasting or the 16:8 diet.
Although intermittent fasting doesn't require you to eat or drink specific food and drinks, it's recommended to follow a healthy, balanced diet where all macronutrients are represented in the right quantities. Drink plenty of water throughout the day but feel free to consume tea or coffee, even when you're fasting, as long as you can drink those without milk/milk substitutes and sugar.
Allow your body to adjust and be in it for the long run. You might lose weight within three weeks, but you can pile the pounds back on just as quickly if you start eating like there is no tomorrow after the diet is 'concluded'. Moderate exercising is recommended as that can help boost metabolism and increase hormone levels.