How To Lose Weight Through Intermittent Fasting

Intermittent fasting is a popular diet trend, but how do you do it correctly to lose weight?

Updated: Wednesday 26 October 2022

Intermittent Fasting

You may have noticed a bit of a buzz around ‘intermittent fasting’ in recent years, a form of dieting that focuses on controlling when in the day you eat. It’s no doubt that the approach has become somewhat popular amongst those seeking to live more healthily, but how much evidence is there that intermittent fasting can be an effective long-term strategy for weight loss? In this article, we investigate whether intermittent fasting can help you lose weight or whether it’s just a fad, and take a look at the most popular methods people use to structure their fasting programs.

What is intermittent fasting?

Intermittent fasting (IF) is an umbrella term for eating schedules that cycle between periods of fasting and eating. Unlike typical forms of dieting that tend to focus on the quantities and types of foods that are consumed, IF restricts which days of the week or which time of the day you eat. Therefore, rather than being a diet itself, you can look at IF more as a pattern of eating. The practice of fasting can be seen throughout human evolution, common today in many religions, but seen initially through involuntary fasting back when our hunter-gatherer ancestors simply didn’t have access to food sources at any time of day. Therefore, one of the arguments in favour of intermittent fasting is that it resembles a more biologically natural eating pattern than the modern Western routine of eating 3 meals a day with the occasional snack in between, and can benefit your health in various ways. There are several popular methods of intermittent fasting, and the nature of IF allows for easy customisation to best suit your needs.

How does intermittent fasting help with weight loss?

Intermittent fasting for weight loss is a well-studied area of research. Perhaps the most obvious effect IF has is how it can automatically reduce your calorie intake. Eating only at specific times means you’ll likely have fewer individual meals over the course of the day, and you’re therefore unlikely to be able to squeeze your usual number of calories into that eating window. Additionally, IF can lead to hormone changes that aid weight loss, such as an increase in the release of norepinephrine, a hormone that enhances the rate of fat loss. [1] Hormone changes are responsible for a short term metabolic rate increase of up to 14%, promoting weight loss. [2] Therefore, IF can both reduce calorie intake, and increase calorie expenditure, and so is a powerful weight-loss tool. Studies have also found that intermittent fasting causes less muscle loss than the typical continuous calorie restriction diet. [3]

Are there other health benefits?

Many studies have been conducted exploring the effects of intermittent fasting on our health, and it’s been shown to have benefits across a host of other areas too.

  • Protect against type 2 diabetes - IF can reduce insulin resistance, lowering the blood sugar levels and reducing the chance of developing type 2 diabetes.
  • Reduce inflammation - one study found that alternate-day fasting led to a reduction in inflammation in overweight adults, particularly those suffering from asthma. [4]
  • Reduce the risk of heart disease - IF can reduce “bad” LDL cholesterol, decreasing your risk of heart disease and stroke. [5]
  • Improve brain health - IF increases the presence of the brain hormone BDNF, which regulates the survival and growth of neurons. It may therefore help to protect against diseases such as Alzheimers. [6]

How to do intermittent fasting

There are numerous configurations of IF that have been proposed, and you may need to trial a few to find which method fits best into your routine and produces the most significant weight loss results whilst maintaining your energy levels. Here are five of the most popular methods of intermittent fasting:

The 16/8 method

The 16/8 method of intermittent fasting involves fasting for 16 hours every day, with your window to eat in being 8 hours. You get to choose the hours in the day where the windows apply, but the most common way to apply this method is by skipping breakfast in the morning and not eating anything after dinner, such as having an eating window between 12 pm and 8 pm. It’s easy to fit two substantial meals into this routine, but many people have three meals or more. This is arguably the easiest method of intermittent fasting to carry out, especially if you’re someone who skips breakfast or eats later in the morning already. During the 16-hour fasting window, you are only allowed to drink water, coffee or another zero-calorie drink. When combined with exercise, this method has been shown to decrease fat mass whilst maintaining muscle mass. [7] Whilst the 16/8 method doesn’t dictate what you eat or how many calories, this approach may leave you low on energy if you eat lots of processed or fatty foods, so try to eat healthily during your eating window and don’t eat an excessive number of calories.

The 5:2 method

The 5:2 method rotates on a weekly basis, where you eat normally for 5 days of the week, and restrict your calorie intake on 2 days of the week. On the fasting days, the recommended calories to consume are 500 calories for women, and 600 calories for men. The 2 fasting days are most commonly spread throughout the week, with normal eating days in between, such as fasting on Monday and Thursday for example. The diet is straightforward, with no rules around when or what to eat on the full-calorie days, and is a lot easier than the below Eat Stop Eat method, but it can still be challenging on the low-calorie days.

Eat Stop Eat method

The Eat Stop Eat method consists of a 24-hour fast, either once or twice per week. For the fast, individuals usually opt to go from dinner to dinner, skipping breakfast and lunch on the fasting day. The same rules around beverages from the 16/8 method apply here. For weight loss, make sure that on the non-fasting days you’re eating the same amount of food as you would normally. This method may be more difficult to implement, but you can ease yourself into a longer fast by starting with a 14 or 16 hour fast and increasing the window as you get more comfortable with it.

Spontaneous meal skipping

With no structure to this method of weight loss, the approach involves skipping meals whenever you feel like it. There may be circumstances where you are not particularly hungry, or if food isn’t immediately accessible, and these are the perfect times to perform a short fast that fits in with whatever it is you’re doing. Many people do this naturally and are able to function perfectly normally, and this is a great way to get into the habit of fasting but without strict rules around timings. However, the other side of the coin is that if you’re not someone who can easily skip a meal regularly, this approach might not provide enough structure for effective weight loss, and results may be slow if not non-existent.

The Warrior Diet

The Warrior Diet for intermittent fasting involves eating only small amounts of raw fruit and vegetables during the day, and eat a large evening meal. Many opt for a 4 hour eating window in the evening to fit in the adequate amount of calories to support their energy levels the following day. The Warrior Diet encourages the consumption of unprocessed, healthy and organic foods in both the feasting and fasting windows. This is a popular method of intermittent fasting, however, the short window of eating may be difficult for many, and overconsumption in the evening can be a common challenge.

How do I maintain my intermittent fasting routine?

The process of losing weight is rarely plain sailing, but you can increase your chances of feeling good whilst intermittent fasting and stick to your eating pattern with the help of these tips.

  • Stay hydrated - drinking plenty of water and other calorie-free drinks such as herbal tea helps to remain hydrated whilst also reducing feelings of hunger.
  • Plan distractions - make sure you’ve got activities lined up to do during your fasting periods, so you are distracted from your hunger and can avoid obsessing over food.
  • Make every calorie count - if your eating plan involves eating low-calorie foods during the fasting windows, select nutrient-dense foods such as eggs, nuts or fish that pack lots of protein, fibre and healthy fats.
  • Eat high-volume foods - foods that are filling yet are low in calories are perfect weight loss foods. Snacks like popcorn contain very few calories (but be careful with the salt or sugar content!) and grapes and watermelons are ideal with their high water content and low calories.
  • Season generously - seasoning your meals with generous amounts of garlic, onions, spices or vinegar helps to pack in lots of flavours whilst staying low on the calories. Really flavourful meals may help to reduce feelings of hunger.

How else can I lose weight?

Intermittent fasting is a great way to promote weight loss, but it should be used in combination with other weight-loss strategies. The NHS recommends at least 150 minutes of moderate exercise (such as cycling) or 75 minutes (such as running) each week, and exercise is important for everyone’s health regardless of their weight. [8] It’s also important to regulate the types of food you consume, not only for your weight but also for your general health. Highly processed foods and those that are high in saturated fats and sugars are best reduced, as these tend to ramp up calorie intake without benefiting you nutritionally.

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Toby Watson

Written by: Toby Watson

Pharmica Medical Writer

Toby (BSc) is an experienced medical writer, producing educational articles on many areas of health including sexual health, fitness, nutrition and mental health.

He particularly enjoys debunking misconceptions around heath conditions and their treatments, researching each topic in detail and writing easily-accessible content.

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