In the health and fitness world, there are two types of people: those who enjoying fed state training (i.e. eating before they exercise) and those who train fasted (so work out on an empty stomach). I, my friends, fall into the latter and it’s for no particular reason other than the fact that I tend to train early in the A.M. and can’t face squatting, deadlifting or running on a full stomach.

But with the ever-growing bank of research and rise (and rise) of experts suggesting that fed state exercise could be the key to many things, like better athletic performance and muscle growth, I was hungry to see if doing so could benefit me and my fitness goals. After all, it’s all about training smarter, not harder, right?

So, after racking the brains of Dr Stacy Sims, a scientist, female physiology expert and author of ROAR, along with registered dietitian and founder of Dietitian Fit, Karine Patel, I made it my mission to exercise in a fasted state for two weeks followed by two weeks of fed-state training.

Over a month, I kept all variables the same, completing the same exercises on the same days for roughly the same amount of time so that I could identify any changes on a level playing field. I also stuck to a pretty similar diet across the four weeks to make sure I was fuelling my body pre and/or post training. Plus, I tried to keep my sleep pattern as regular as possible, heading to bed around 9.30pm (wild, I know) and waking up around 6.30am.

To find out the tea, along with the benefits and negatives of fasted vs fed state training, and whether one really is better than the other, keep scrolling.

My weekly exercise routine

Throughout the four weeks, I kept things BAU with my exercise schedule and for good reason. By doing so I had a better chance of completing the workouts and therefore being able to compare and judge fairly the differences I noticed when exercising fed and fasted.

I love strength training (whether it’s free weights, bodyweight workouts or Pilates) and try to do this type of exercise around four or five times a week (depending on how zapped I’m feeling), splitting workouts into lower, upper and full body sessions.

Compound movements, like squats, deadlifts and chest press are a firm fave, but in the last couple of months I’ve added in some more core-specific workouts to try and strengthen this area. I also try to run outside once a week, but with the darker mornings and nights, motivation levels are often lacking. So I tend to switch this up with skipping.

This means my four weeks of training looked something like this:

I stuck to my usual rest days (they are absolutely necessary for me and needed). And for the two weeks when I trained in a fasted state, as its name suggests, I consumed absolutely nothing before working out. During my two weeks of fed state training, under the guidance of sports dietician Patel, I devoured breakfast roughly two hours before training (like porridge or eggs), or a snack high in simple carbohydrates 30 minutes to one-hour before (like a banana or half a bagel).

But first things first: fasted vs fed state training — what are they?

Very good question. Well, to be absolutely clear, according to Dr Sims, fasted training is when you complete a workout without having any fuel two or more hours prior to exercise.

Meanwhile, Dr Sims defined fed state training as exercising in the first few hours after eating. She said: ‘[This is] pretty much the time when your body is absorbing the nutrients and responding in kind by increasing blood glucose, insulin, reducing appetite stimulatory hormones, reducing cortisol (AKA the stress hormone) and epinephrine (otherwise known as your body’s fight-or-flight response).’

What are the benefits of fed state training?

Egg muffins are a go-to ahead of fed state exercise

As it turns out: there are a myriad of benefits of training after tucking into your avo on toast, overnight oats or omelette. According to Dr Sims, this includes:

• Decreased sessional rate of perceived exertion (RPE) — so in other words, tough sessions might not seem so hard.
• Increased anaerobic capacity — Meaning? You can train harder for longer.
• Improved signalling of muscle protein synthesis post exercise — which is also great because this helps with the body’s process of building new muscle.
• Reduction of cortisol during and post exercise — ’Or rather, a reduction in the change in cortisol as there is less need to produce it to provide fuel for the working tissues,’ Dr Sims explains.
• Attenuated signalling to the hypothalamus (the part of your brain which is responsible for maintaining your body’s internal balance and connecting your endocrine system and your nervous system) for alterations in endocrine function, i.e. the process of releasing hormones. Although Dr Sims mentions you will ‘also need to eat after exercise, within 45 minutes to stop the feedback to reduce endocrine function.’ So this is where the best protein shakes step up to the plate.
• A 2018 review published in the Scandinavian Journal of Medicine & Science in Sports also found fed state training can lead to increased aerobic capacity, which is great, because the more optimally your body can utilise oxygen the more physical work you’ll be able to do.

What are the negatives of fed state training?

I use an upper- and lower-body workout split

In terms of the negatives associated with eating before exercise, some people may feel sluggish or too full eating too closely to working out, especially if the food has not yet been digested.

Some might also feel nauseous (hello me), which one study proved is more likely to happen on a full stomach. ‘Therefore it is really important to consume the right food before exercise and to test how we react to certain food before a sports event,’ Patel advises.

And according to Dr Sims, some people may eat too much so it will ‘impact exercise capacity.’ Which leads me to my next question: how much fuel should we eat before working out?

‘The goal is to have around 120-150 kcal to increase blood glucose levels, drop cortisol responses, and improve exercise capacity,’ Dr Sims answers. ‘Research shows around 30g carbohydrate is adequate before cardio, while pre-strength, 15g protein would be enough,’ Dr Sims says, although a combination of both carbs and protein would be the ideal. ‘If the session is over 90 minutes, then fuelling during the session [stopping for a snack mid-workout] is needed,’ she adds.

What are the benefits of fasted training?

The jury’s still out on this one. Dr Sims says that when it comes to fasted training there are ‘no positives for women’. While Patel tells us: ‘Much of the evidence carried out into fasting and training has been done in men, not women, so it is hard to completely know the benefits, if any, for women to train fasted.’

For years, we’ve been fed the fact that fasted cardio on an empty stomach means you’re more likely to burn fat. And on the surface, this statement is true.

But according to a 2016 meta-analysis published in the British Journal of Nutrition, researchers found that this is purely an acute effect. Meaning? ‘Although the fat burning is higher during the workout, the research shows that this does not lead to an overall greater body fat loss in the long term,’ Patel explains. Read on for more…

What are the negatives of fasted training?

A recent 2023 review concluded that training in a fasted state (for this study specifically, meaning when there are low amounts of carbs in the body) can impair muscle protein synthesis and anaerobic performance.

While if you train fasted, research concludes that you’re more likely to tap into lean muscle as an energy source as the body is trying to conserve all fat and carbohydrate stores for critical reproductive functions.

‘My most often reply to a woman that tells me she is doing fasted training to positively influence body composition is “Really? Are you wanting more body fat and less lean mass?”’ Dr Sims questions.

My learnings

Before I jump into what I’ve learned over the course of four weeks, know that this was done in the name of journalism, and WH would not recommend undergoing the same challenge without professional expert guidance. What’s more, every body is unique, so if you were to compare the effects of fasted and fed state training on yourself, it’s likely we’d have some very different results. Use my learnings to inform your workouts, but remember that feedback from your body is the most important thing.

1.It’s not ‘normal’ to feel consistently tired

Two weeks of fasted training was first on the schedule, purely because fasted exercise is all that I know and all that I have known for the past few years, so why change a good thing?

After said two weeks, I felt how I usually feel: tired. But isn’t that just everyone? Aren’t we all ‘tired all the time’ or TATT? (Which is the acronym the NHS introduced for this term because it’s become so common). Hindsight is a wonderful thing and it’s only after fed state training that I’ve come to the conclusion that it doesn’t have to be this way. Who knew?

2. Fed state training made me feel more awake



Patel advises against protein shakes during a workout, but recommends fruit smoothies

Now it’s no secret that we have gut health to thank for multiple things, from being able to deal with eczema to IBS. But did you know that your gut microbiome has its own internal clock and follows a 24-hour cycle?

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This is something I found out first hand by fed state training. Of course, we all know food is fuel but soon after my body had digested my breakfast, I felt more awake and ready to take on the day and work out, as my gut had been awoken from the food. Not only did this leave me feeling on cloud nine both mentally and physically post session, but it meant I could tick off a much more effective workout, too.

3. Fed state training = more sustained energy



Fed state training gave me more energy during and after workouts

This wasn’t just the case before and during my sessions- personally, I felt like the effects of eating before working out stayed with me throughout the entire day.

During fasted training, I would usually get an endorphin hit straight after working out and I could ride this wave until around 2pm. But at that point, I’d reach for my last coffee of the day and suffer that undesirable 3pm slump, plodding my way through to the 5pm finish with my energy store depleted.

Since starting fed state training, I’ve said see ya later to that 3pm slump and good riddance to 5 o’clock tiredness. I did often question whether this was purely a placebo effect, but after speaking with Patel, there is evidence to suggest otherwise.

‘Fuelling before a workout, especially with simple carbohydrates (such as carbohydrates in the form of sugar or starch as these are digested and absorbed quicker and readily available for fuel) can improve performance and possibly allow training at a higher intensity,’ she explained.

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‘This is because the carbohydrates consumed can be used as fuel for exercise, and if protein is consumed, this can start to be digested and get ready to be used for repairing muscles post exercise.’

4. Timing is everything

During my fed state training sessions, I found that training a couple of hours later worked best for me. Essentially, it meant I could eat a little bit later, let my food go down, and still tick off my exercise before 9am without feeling nauseous.

According to research, there is a best time of the day for women to exercise (spoiler alert: it’s in the mornings) and I, for one, agree with this. But morning exercise won’t be right for everyone. Some days, finding the motivation to move is difficult enough, so putting another barrier in the way is like adding fuel to the fire. The best time of the day to train is whenever it works for you.

5. Tailoring your foods is key



I often go for a peanut butter bagel before strength training

If there’s one thing we can agree on, it’s that food is personal and what works for one may not work for all – not least in terms of enjoyment. And the same can be said for the different types of exercise.

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For example, when I completed my running, I found I couldn’t stomach anything other than a banana (runner’s stomach is real). Whereas my 45-minute strength training session? Fuel me up. Whether it was half a peanut butter bagel, an egg muffin or a protein yoghurt, I could digest these foods much easier and power through my workout.

As someone who finds it difficult to stomach lots of food before working out, Patel recommended a few things. ‘A banana is a great idea, or any other easy to eat fruit such as berries or grapes, to provide an easy to digest source of carbohydrates,’ she told us.

But as for taking a protein shake to the gym? This is something Patel advises against. ‘Due to the high content of protein and low carbohydrate, this wouldn’t provide much fuel right before a workout,’ she says. ‘But a smoothie made with milk, banana and fruits could work very well, as liquid calories tend to be digested quicker than a whole fruit.’

My verdict

After just three days of fed state training, I really noticed the difference I felt in myself. On this particular day, I was lower body training (which I always find harder to do than upper-body exercises) but through the 45-minute session, I remember feeling wide awake, raring to go and as though I could squat, lunge and leg press heavier weights than usual.

At the end of my two weeks of fed state training I no longer felt like I was on a treadmill of exhaustion, or as though rolling out of bed and exercising was an uphill climb. Instead, I felt energised, stronger and like I was actually making headway with my training.

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If I’m completely honest, I still find it tricky to eat before running, as I can just about stomach a banana but as Patel says, that’s enough, and I don’t think I’d ever train entirely fasted again. For me, the experts’ insights weigh hugely on my mind and I’m a big believer in listening to your body. And if I already feel better after two weeks of fuelling before training, why would I stop now?

By completing this challenge, it’s solidified to me that eating something before I work out works better for me — both for my body and mind. However, to do so, I’ve had to alter the time I work out slightly. Shifting my exercise half an hour to an hour later has meant I’ve had time to digest my food, and then to reap the rewards while I train.

Feeling more energised and stronger has been the most significant change for me, but I’ve also noticed an improvement in my sleep. I always try to prioritise shut-eye (hello 9pm bedtime) and I’d say I’m a good sleeper, but if my ability to hop out of bed (even on these icy cold mornings) is anything to go by, the quality seems to have improved.

Two weeks isn’t long enough for me to have noticed any aesthetic differences, such as muscle growth, but the aforementioned factors have been so substantial that I can confidently say fed state training is something I’m going to be sticking with.