intermittent fasting - sustainable weight loss

Is Intermittent Fasting Sustainable?

If you’re interested in cutting your calorie intake and losing weight, intermittent fasting is something you’ll have come across in your research. Used by celebrities like Hugh Jackman to achieve a lean figure, there is a lot of hype around the intermittent fasting lifestyle. For some, intermittent fasting sounds extreme, which leads us to an important question:

Is intermittent fasting sustainable for weight loss?

What Is Intermittent Fasting?

Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting. Intermittent fasting is not a diet; instead it’s a dietary pattern, meaning it does not dictate which food should be eaten — but when food should be eaten. Intermittent fasting is currently very popular among the health and fitness community because it essentially allows you more freedom in your diet, stopping you consuming excess calories because your window for eating is so limited.

There are several different intermittent fasting methods:

  • The 16/8 method: Fasting for 16 hours per day and eating during the 8-hour eating window (e.g. skipping breakfast, eating your first meal at noon and your last meal before 8 pm)
  • The 5:2 diet: Eating as normal for five days of the week then eating 500-600 calories on two days of the week
  • Eat-stop-eat: The practice of a 24-hour fast once or twice per week (avoiding eating after dinner one day until dinner the following day)

The most popular method of intermittent fasting is the 16/8 method. Working individuals who struggle to find extra time in the morning may find this method convenient. It is also convenient for those who exercise in the evening and tend not to require as much energy in the morning.

Is Intermittent Fasting Necessary for Weight Loss?

The short answer is no — you don’t need to commit to intermittent fasting if you want to see success in your weight loss program. So why do people even consider intermittent fasting in the first place? Well, as your eating window is restricted, this will naturally result in you eating less food (unless you binge on huge amounts of food), which can technically result in weight loss.

In its most basic form, weight loss works through a caloric deficit.

Your body is in a constant state of energy consumption. The energy your body needs is obtained through calories, which are present in all food. Your body is always using the fuel you put into it (food) to operate — you need energy for everything from movement and breathing to thinking and digesting. Everyone has a base caloric requirement to survive that varies depending on age, gender, weight, height, metabolism and several other biological factors. The amount of energy you need is also increased with exercise, as the body then needs more fuel to function. This is why exercise is such an important part of weight loss. It doesn’t burn away fat itself, but it means your body needs more energy to perform its basic biological functions.

This is also why a great and sustainable diet is so important for losing weight alongside exercise — which leads us back to the idea of intermittent fasting.

If you eat fewer calories than your body needs to operate, you will use the energy stored within your body fat. If you ingest more calories than your body needs, it will save those calories to support survival during leaner times. So the essential formula for weight loss is this:

Less food eaten = decreased calorie intake = weight loss.

And so, people commit to intermittent fasting diets. The core idea behind intermittent fasting is if you are eating over a shorter period, you are eating less food. If you are eating less food, you are eating fewer calories, which creates the environment required for fat loss. Some people even suggest that intermittent fasting is superior to other forms of caloric restriction, but research does not support this.

Trepanowski et al. (2017) found intermittent fasting is not superior to daily calorie restriction with regards to adherence, weight loss, weight maintenance, or improvement in risk indicators for cardiovascular disease. Another small-scale study found that traditional calorie-restrictive dieting plans were more effective for weight loss than intermittent fasting.
So, everyone carrying out intermittent fasting is wrong?

When Intermittent Fasting Works

The short answer is again no.

Every side of the argument has a study to back up their claim. While we can tell you about lots of research that shows intermittent fasting doesn’t work as well as other methods, another nutritionist and personal trainer who supports the technique of intermittent fasting will probably quote you a totally different study on why it does work.

Intermittent fasting can work when it works for your lifestyle.

Some people don’t eat breakfast. If you simply cannot stomach food in the morning or if you can’t make time for breakfast, then intermittent fasting can become a sustainable food intake pattern.

David Higgins, trainer to stars like Margot Robbie and Claudia Schiffer, is one such advocate of sustainable intermittent fasting. He tells people that the 16/8 method is a good strategy for losing weight, but only if it works as part of your lifestyle.

This idea is supported by Harris et al. (2018), who note that if you aren’t making any changes to your current eating habits, then intermittent fasting can be a sustainable weight loss tool. The study found intermittent fasting may be an effective strategy for the treatment of overweight and obesity and is more effective than no treatment. Furthermore, Patterson & Sears (2017) found that an intermittent fasting regimen may be a promising approach to losing weight for people who can safely tolerate intervals of not eating, or eating very little, for certain hours of the day, night, or days of the week.

The key point here? It’s all down to the individual involved.

Sustainable Intermittent Fasting: Why It’s Not Always Possible

Healthy and sustainable weight loss is driven by dietary plans that work for an individual. If you dislike the way you are eating, then you won’t stick with it. Willpower supports quick results, but it doesn’t keep you healthy long term. The only way intermittent fasting can be sustainable, just like with any other weight loss strategy, is if you can make it part of a lifestyle that makes you happy.

If by conducting intermittent fasting, you are feeling hungry in the morning and lethargic until you eat lunch, it’s not for you. You cannot reasonably expect to maintain a sustainable weight loss program through intermittent fasting if you hate it. This is why studies show other diets work better for some people, but then sometimes intermittent fasting works for another group. It’s because it can work for you, but sometimes it won’t.

Intermittent fasting is not a magic bullet for weight loss. There is no true magic bullet that will guarantee you the best results. We’re all different, which means if you want to lose weight, you have to find a way of doing it that works with your life. You may try intermittent fasting and love it. Intermittent fasting may be unbearable for you.

Both reactions are absolutely fine.

When you want to lose weight, it’s about finding your happy medium. Your perfect balance. Sustainable intermittent fasting is a good state of mind, where you don’t have to work to achieve it. It’s not a battle to overcome adversity.

You might say that weight loss is all about willpower and commitment; dedication and pushing through. We’ve all been taught to think this, but it’s not the truth. All the happy and healthy people in your life. The thin friends you always envy. Are they constantly battling to keep their weight down? No. Are they just lucky to have faster metabolisms than you? No.

It’s their lifestyle that results in their good health. You can find a lifestyle that does the same.

Intermittent fasting may be part of that, but it might not be.

The Cons of Intermittent Fasting

Don’t get us wrong, if intermittent fasting works for you, then use it. Finding a lifestyle that supports sustainable health is probably the biggest challenge you’ll face on your road to weight loss. There is a lot of trial and error. Whatever works, use it to your advantage. However, we’re all about honest and genuine advice at The Sports Dietitian, so we want to make sure you are equipped with all the necessary tools to secure a brighter future for yourself. With that in mind, here are some critical things to know about intermittent fasting:

Reduction in Metabolism

This news is going to set off alarm bells. For those unsure of how metabolism impacts weight loss, metabolic rate is the speed at which you turn calories into energy for your body — the higher your metabolic rate, the more calories you need to sustain your current weight. So, if you have a high metabolic rate, weight loss is easier. A reduction in metabolism is the last thing anyone trying to lose weight wants.

The longer we are in a fasted state thanks to intermittent fasting, the longer we experience something called catabolism, which is the breaking down of muscle tissue to provide the protein we need for basic bodily function. This state is strongly related to reducing our metabolism.
Small, frequent protein feedings of 20-30g five times a day are superior for maximising protein synthesis, compared to consuming protein in larger doses, less frequently as you would with intermittent fasting — Burke et al. 2010.

Protein synthesis is a key ingredient to enable us to maintain our muscle mass when adhering to a calorie deficit to achieve weight loss. There is a direct correlation between muscle mass, metabolically active tissue and metabolism. The more muscle mass we have, the higher our metabolism. Put simply, the more muscle mass we can retain, the more calories we can eat before gaining body fat.

And let’s face it — who doesn’t want to eat more when they can?

Therefore, when we fast, we reduce the effectiveness of protein synthesis, which negatively affects the amount of muscle mass we can retain during a calorie deficit (eating fewer calories than we are burning off). This, in turn, can reduce our metabolism and make achieving sustainable weight loss more difficult.


If your body is not adapted to life without food — either through skipping breakfast, lower-calorie days, or two days fasting a week — you’ll experience hunger. Hunger is a massive demotivator. The sudden drop in glucose levels that comes from a lack of food impacts our state of mind, our energy levels and can leave us feeling frustrated. It’s tough to stick to a diet plan when you’re hungry, which means you’ll probably relapse into old behaviours.

Why do we eat? We eat for enjoyment, health, and cultural benefits. We eat to survive; we eat to perform physically and mentally. When fasted and hungry, our reaction time, problem-solving abilities and ability to keep our cool during stressful situations greatly reduces. So, if you want to be at your best during the morning, and breakfast is a part of that, make sure you eat instead of suffering through needlessly.

Poor Training Results

If you’re a morning exerciser, then intermittent fasting is unlikely to be sustainable. You need the energy to train. Energy comes from food. Training fasted without efficient fuel for energy will be a thorn in your side. There is a world of evidence supporting the importance of carbohydrate pre-exercise to maximise performance (Burke, 2017). No food in your system, no energy in your muscles, poor performance in the gym.

Bad Breath

A final one to think about, intermittent fasting can lead to reduced salivary flow, which is linked with bad breath. If you’re struggling with confidence and self-esteem in public due to your weight, bad breath is the last thing you need.

Sustainable Intermittent Fasting: Key Takeaways

Intermittent fasting is not necessary for weight loss and does have a lot of downsides. There are positives of intermittent fasting and it can help you — but only if it’s sustainable intermittent fasting that works with your current way of life. Don’t even try intermittent fasting if you love breakfast or get hungry between meals. It’s not going to work. It’s not sustainable.

If you love to eat, there is an easier way.

Eating a well-balanced diet, with the correct macronutrient structure will minimise hunger, maximise food palatability and eliminate the feeling you are on a diet. Really, diet is a nasty word we want to avoid. You don’t ever want to be on a diet — you just want to be eating well.

The key to sustainable weight loss results is discovering a convenient eating structure with regular accountability, motivation and behaviour change support that works for you. And let’s face it — if we are making an effort to adapt our current eating habits, the results we obtain had better be sustainable.


Want to find an eating plan that works for you? I will help you discover the ultimate lifestyle for your weight loss. One you love. One that drives you and excites you every day. Not one you hate and just want to be over. We’re not about quick fixes at The Sport Dietitian — we’re about results that stay with you for a lifetime. Don’t rebound to bad habits because you can’t live in your diet hell forever. Book a free fitness consultation with me today. Feel less self-conscious in how you look, live longer and gain clarity on the optimal evidence-based nutritional strategy for your sports performance.
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