Ultimate Guide to Intermittent Fasting for Weight Loss
Intermittent fasting is a way of eating that is actually nothing like most diets. People who implement it swear by its benefits, and the results can be both eye-opening and impressive. And most of all, this behaviour change means that the weight typically stays off, which is half the battle (and one that fad diets don’t help win).
But it’s also harder to understand. Unlike the paleo diet (meat-heavy) or the Atkins diet (carb light), intermittent fasting doesn’t put a whole lot of emphasis on exactly what you eat.
Instead, the focus is on when you eat and also how much you eat.
This post is a high-quality, no BS guide and primer into everything to do with intermittent fasting. It includes:
- An introduction to the benefits of intermittent fasting
- Why intermittent fasting is aligned with how humans evolved
- Different types of intermittent fasting to consider (there’s no ‘one size fits all’ way to do it)
- How you can customise your choices with intermittent fasting
- Other things to consider before you try it
- Some ‘frequently asked question’ about intermittent fasting
The Big Benefits of Intermittent Fasting
The main benefit of intermittent fasting (and likely the reason you are reading this article) is that it is a proven and sustainable way to lose weight. More specifically, it appears that this way of eating has the effect on the body of losing fat, while retaining muscle mass.
Elite athletes who most definitely need to retain their muscle mass, power and flexibility (and, therefore, can’t afford to lose muscle weight) are known to use intermittent fasting as a way to retain lean muscle while losing body fat. That makes a strategy like intermittent fasting ideal for people like those who follow the Maxine's training and diet programs.
It also can’t be overstated how helpful it is that intermittent fasting is a simple, easy-to-follow regime.
Too many diets and meal plans are fads or so complex that they become almost impossible to actually follow out in the real world. For example, it might be possible to eat the majority of your calories from lean meat, nuts and fats while avoiding sugar and carbohydrates if you are a professional sportsperson or celebrity with a personal chef. But for regular people who shop at supermarkets, have a budget and demands on their time, it’s far less achievable. In contrast, intermittent fasting is simple to understand and simple to actually put into action.
Intermittent Fasting: Grounded in How We Evolved
Intermittent fasting is not a new concept. In fact, it’s one of the oldest dietary patterns out there. And by ‘old’ we don’t mean that it began in the 80s as a way for bodybuilders to cut before competitions.
It began thousands of years ago through sheer evolutionary necessity. Before it had a proper name, intermittent fasting was just how humans lived. Comparing the two lifestyles of then and now makes it clear why that’s the case.
Today, every Western and developed nation has an issue with obesity and the associated health issues of heart disease, diabetes and many other chronic diseases. Simple facts and maths show that weight gain is caused by some combination of excessive calorie consumption and lack of movement and exercise. Genetics also plays a part.
Compare that to our evolutionary past. Calories were scarce. Food had to be foraged for, and foraging yielded low-calorie density things like berries, mushrooms, edible plants and insects, such as grubs. The other food source was hunted food in the form of animals. That food source was higher in calories, higher in protein and energy-dense. But it had to be stalked, hunted and killed. And as a result, it was hard to come by and not a major feature of the overall diet.
Our hunting and gathering past meant our bodies evolved in a way that prioritised a functioning body in the event of long periods of low or no calories from food. Which makes sense. If a species was not able to be certain about where the next meal would be sourced, then it makes sense that the biology of that animal would adapt to deal with that reality.
As a result of that background and evolution, the human body is a highly efficient engine. It doesn’t require huge amounts of calories to operate on any given day. And it also is able to draw from reserves of energy (stored in the body) when food and nutrition are not readily available to continue to function at a high level. It’s a little like a hospital being able to switch to on-site generators if the ‘mains’ are taken offline due to a sudden storm: all of the critical functions and machines will continue to operate without interruption.
How Intermittent Fasting Works in Your Body
So now you know that we’ve evolved to be able to function at a high level without constant food, you might be wondering, ‘how does it actually work?’
It helps to think of your body basically existing in three separate phases.
- The ‘food consumption + digestion’ state – this state begins when you eat, and continues throughout the process of digesting food and absorbing the nutrients it gives you. The time that takes differs depending on your metabolism and whether you are male or female, but let’s just call it four hours. When a body is in a non-fasted state, it typically will not burn many calories. That’s because it is digesting and ‘storing’ any excess and is in a calorie surplus for that time.
- The ‘after digestion’ state – this state begins when the previous one ends. This period is when your body is not digesting and absorbing the nutrients from a previous meal. But importantly, it also isn’t drawing on previously stored energy. This period lasts around 10 hours.
- The fasted state – this is the key time. About 10 hours after the ‘after digestion’ state ends, the body enters the fasted state. This is when it accesses previously digested and stored energy. This is the phase when it is easiest to burn fat because your body is ‘drawing down’ on its reserves. And when it comes to energy, the body stores this incredibly efficiently as fat. So, by entering the fasted state, you are giving your body permission to access those reserves of energy to fuel your day.
You can see the simple logic of the above explanation:
- Your body stores excess energy in the form of fat.
- If you eat regularly throughout the day, it never has to ‘access’ this stored energy.
- If you increase the amount of time between meals to get to the ‘fasted state’ then you are giving your body permission to access this stored energy.
- If you enter the fasted state and burn stored energy, then this stored energy (fat) will be consumed by your body.
All that is required to enter the fasted state is to have the required gap between eating so that your body can move from the non-fasted state to the after-digestion state and finally to the fasted state. On average, the total time taken to get to the fasted state is 14 hours after a meal is consumed.
So, now that you know how it works, we can move into looking at how you can implement this approach in your own life in a way that suits you.
No One Way: Choosing the Type of Intermittent Fasting That Suits You
One of the most helpful things about intermittent fasting as a weight-loss strategy is its flexibility.
There is one key thread across all of them: calories are restricted to much lower levels than an otherwise ‘normal’ day of eating. But beyond that, there are a surprising number of variations to choose from on the same theme.
And the encouraging thing is that these variations have been there for some time now. That means that a range of health institutes and universities have done research and experimentation on these variations. The results suggest that each of the following ‘twists’ on intermittent fasting have been shown to be effective in different tested populations.
So, we’ve prepared the following list for you to read the following list as an introductory menu of options. There is no single ‘right or wrong’ option or ‘best’ approach. The best approach is almost certainly going to be one that works for you and that you can stick to over the long term. It’s that consistency of effort and application that will drive the greatest results in terms of weight loss.
Occasional Intermittent Fasting Options: The 5:2 Fast
The 5:2 fast, or the 5:2 diet, is one of the more popular fasting methods that has emerged in recent years. Part of that has been attributed to it being examined and publicised in television specials by well-known presenters.
The 5:2 fast is very simple. For two days of the week that aren’t ‘back to back’ a person on the 5:2 diet would consume just 500 calories. These calories would be ‘tilted’ towards the more satisfying macronutrients containing high protein content, like fatty fish or lean red meat.
As a point of reference, 500 calories is about 25% or one-quarter of what you would consume if you ate three meals plus a small snack or two on a more typical day of eating. The benefits of this method include the ability to pick and choose just two days of the week to fast to gain the benefits. So, during the holiday season, a person might choose to do both of their fasting days on weekdays, so that they could enjoy summer BBQ’s and catch ups with friends on weekends without calorie restrictions.
The 5:2 method is also easier for many people to stick with long-term because it doesn’t require consistent, daily compliance to show results.
The downsides to this method are also fairly clear. On any given day, 500 calories is not a lot of energy. It’s roughly equal to a single large meal (though someone doing the 5:2 method would likely spread these 500 calories across several smaller meals). For the majority of people, the 5:2 diet will leave them hungry for part of the day. However, this is more keenly felt early on when the body is adjusting to the new stresses being placed on it. This discomfort is similar to the ‘good’ discomfort that we feel in our bodies when we take up a new workout routine or exercise program. However, for those with very active training schedules that don’t allow for a day off (e.g. elite athletes) and for those with jobs that are physically demanding (labourers, some trades) this option might not provide enough energy to complete the required tasks of the day. For those people, the ‘fasting window’ might be more appropriate.
Occasional Intermittent Fasting Options: On/Off Fasting
This method of intermittent fasting is a close cousin of the 5:2 diet. Exactly like the 5:2 diet, it has its followers consume 500 calories daily (about 25% of the normal calorie intake for a day). Every ‘other’ day, you would eat as normal.
The net result of this method is that there are seven days in every 14-day cycle that are ‘fasting’ days. This results in significantly more days in a fasting state than the 5:2 diet. The benefits of taking this approach are more rapid results. This more intense option can also be taken if a person has fasted previously and knows that they can handle calorie-restricted days. It is also handy as a shorter-term ‘booster’ to get some early results. It’s also a simple method to follow.
The downsides in terms of energy availability are the same As with the 5:2 diet. And for anyone doing regular training and exercise of any kind, it is helpful to keep an eye on aligning your training days with the ‘off’ days so that the body has adequate stores of reserves to draw on during workouts.
Daily Intermittent Fasting Options: The 16:8 Fast
The 16:8 fasting method involves not eating for 16 hours each 24-hour period. It follows that people who use this option are then eating all of their calories for the day within an eight-hour window.
The 16:8 fast method is one that is used daily. It simply splits each day into ‘fasting’ time and ‘eating’ time. In a regular 24-hour cycle of time, the average amount of sleep is eight hours. That leaves just eight further hours of ‘fasting’ time in the day.
Benefits of the 16:8 Method
This method of fasting feels more achievable for many people, especially those new to fasting. That’s because it doesn’t require especially strict calorie restrictions to hold back from eating ‘normal’ amounts of food for a whole day.
This option also allows for some tailoring depending on lifestyle and goals. That’s because this 16-hour fasting period can begin at any time of your choosing. Imagine that you are in the good habit of going for a run or doing yoga each morning. But after that exercise, you find that you are hungry and low in energy before your work day begins. Normally, you’d have a protein-rich breakfast and a piece of fruit after exercising to get that energy back.
So for you, beginning your ‘fasting period’ as soon as you wake up might not be ideal. You might prefer to eat after your regular exercise in the morning to help maintain that habit. That would mean you would begin your fasting period later in the day. If you went to sleep at 10 pm and woke up at 6 am each day, that would mean that your fasting period would begin at 2 pm.
On the other hand, for someone who normally skips breakfast or has a very small morning meal, beginning the fasting period at 6 am and continuing it until 2 pm (eight hours sleep plus eight hours ‘awake’ fasting for a total of 16 hours) might be a much simpler option that they can stick to better.
Other Things to Consider with the 16:8 Method
Social considerations also play a factor in choosing the best ‘fasting window’. For example, if your work or social life involves multiple lunches at 12:30 pm or dinners with colleagues or friends, then it’s unlikely that a fasting window that includes these meals will work very well for you. The key to this daily fasting method is consistency, so it’s best to pick a window that you are most likely to stick to.
That need for consistency is also a downside for some people. The 16:8 fast is attractive because it is not as restrictive in terms of calories as other fasts, which means that, on average, people following it can eat more. But in terms of downsides, it requires daily adherence. That’s why some people who have variable work schedules or want to have a few ‘days off’ will prefer other options like the 5:2 method.
Training, Health and Medical Conditions: Other Things to Consider if Intermittent Fasting
Intermittent fasting has been shown to be a safe and effective way to lose weight in a sustainable manner.
But just like with any health matter, common sense and personalisation is required. We can’t give any medical advice here because we don’t know your medical history and dietary needs. But if you have any ongoing health issues, take medication on a regular basis or are managing another medical condition (such as diabetes, high blood pressure and many others) we strongly encourage that you speak with your doctor before beginning intermittent fasting.
With that said, we’ve laid out some things to think about before starting intermittent fasting that you can think about so that when you do speak to a health professional, you can ask some informed questions. That will help you work with your provider to take the best approach that is tailored to your individual facts and circumstances.
Common Questions and Concerns
Isn’t it really hard to not eat for 16 hours at a time/to only eat 500 calories a day?
There’s no doubt that reducing your eating window or your total energy intake is hard. You know what else is hard? A time trial five-kilometre run. A punishing 30-minute HIIT class. An intense 90-minute strength and muscle gain weights routine. But plenty of us do one or all of these things.
We do them because they are hard. And we do them because there is a larger goal we are aiming for. Intermittent fasting is not as easy as just eating three meals plus snacks each day. But those who choose to do it are usually aiming for a goal like increasing their confidence or hitting a training goal by increasing lean muscle mass or reducing body fat percentages.
Isn’t skipping meals bad for you?
This is something we hear as kids and usually applies to breakfast. And it’s true that for growing children and teenagers, skipping meals is generally a bad idea. But plenty of things change when we become adults. And intermittent fasting isn’t a social-media backed fad diet. It’s a science-backed and well-studied way of sustainably losing weight and burning fat that is recommended by many doctors.
I want to try it but don’t think I can do it!
That’s a totally normal thought! If you are looking at trying intermittent fasting, remember, you can ease into it by doing just one day a week or maybe reducing your calories by 20% each day until you reach 500. Just remember that like with anything, it’s likely to be most difficult when you start out, and it’ll get easier as you do it more.
Intermittent fasting is a science-backed way to reduce body fat and lose weight while preserving lean muscle mass. It has worked for thousands of people, and depending on your medical circumstances, could be a fantastic option for you.
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