Fuel up or wait it out? How long to wait after eating before exercising

Ever wondered whether it’s best to exercise on an empty stomach or a full one? Should you grab a banana before your morning jog for a quick energy boost, or after to replenish your body? Is a protein shake best drunk ahead of your weights session or straight afterwards? And what about running after a big lunch?

To help you figure out what and how much you should eat, and when, here’s our guide to meal timing and exercise.

Should I eat before or after exercise?

There’s actually no one-size-fits-all answer to this one. It really comes down to individual preferences and needs — including how much exercise you’re doing, the intensity of the exercise, and how food makes you feel once you’ve eaten it.

For example, if you’re heading out for a 2-hour jog, you’ll likely need some fuel beforehand to keep you going. But if you’re getting up early in the morning for a 30-minute walk around the block, you might be able to keep your hunger at bay until you get home.

You may also find that exercising on a full stomach makes you feel a little queasy, or exercising on an empty one leaves you with low blood sugar and makes you feel lightheaded.

Aside from your own preferences, there’s also varied research on the link between meal timing and exercise.

On one hand, several studies have shown that eating carbohydrate-rich foods a few hours before doing endurance workouts can improve workout performance and boost levels of glycogen (a form of glucose that your body stores in case it needs energy) in the muscles [1][2].

On the other hand, different research has demonstrated benefits to eating after exercise instead and working out on an empty stomach — including improved utilisation of fat tissue and consequent weight loss [3].

And just to make things even more complicated, there’s also research that suggests if you’re doing a weight training session, you should eat before and after to enhance results in strength and muscle gain [4].

One thing many researchers do agree on, though, is that if you’re doing any kind of endurance exercise — like running a marathon — you should eat something beforehand to deliver sustained energy throughout your workout. However, this is where the timing of your meal becomes crucial.

What is the recommended gap between exercise and meals?

Again, this often comes down to your preferences, what and how much you’re eating, and whether you’re eating before or after exercising.

But as a general rule of thumb, if you’re eating beforehand, your meals should become smaller the closer you get to your exercise session. If you’re having a big meal, ideally you want to wait a few hours before exercising. But if you’re just having a small snack, you can probably work out sooner.

Your meals should also change in composition. In other words, the breakdown of carbs, fat and protein should be different according to when you’re eating — but we’ll get to that shortly.

And if you’re eating after you exercise, you can really eat as quickly as you want. Preferably, the sooner the better to replenish your muscles and support recovery.

How long after eating should you exercise?

If you’re having a full-sized meal beforehand, you generally want to leave a gap of about 2-4 hours between eating and exercising. This is because it takes time for your body to digest what you’ve eaten and deliver the energy to your muscles. Plus, exercising too soon after a meal can leave you with tummy problems.

There’s also some evidence that timing your meal can affect both your athletic performance and your body’s use of fuel. Research has shown that if you’re doing endurance exercise, you should eat a meal high in carbs about 3-4 hours beforehand to get the most out of your workout [2].

Is it okay to exercise after 30 minutes of eating?

This really depends on what you’ve eaten.

If you’ve just had a big meal, you might want to hold off on heading to the gym straight away. Your body likely won’t have extracted the energy it needs from your meal, and you may find yourself feeling queasy while you’re digesting what you’ve eaten.

But if you’ve only had a snack — like a piece of toast, banana, grapes or energy bar — you likely won’t need to wait as long. Instead, you can probably head out 30 minutes to an hour afterwards, or even immediately.

What happens if you exercise right after eating?

The biggest issue with eating a lot right before you exercise is that you can suffer tummy problems — think nausea, cramping, bloating, reflux and even vomiting or diarrhoea. 

This is mostly the case with more strenuous exercise though, so if you’re going for a light walk or a gentle yoga session, you might not notice any side effects.

Another drawback of exercising immediately after eating is that your body won’t have enough time to draw enough energy from your meal. You may find you feel really sluggish during your workout, leading to less-than-optimal performance.

When should you eat after exercise?

Prefer to chow down after your exercise session? If you’re eating post-workout, aim to do so 15-30 minutes afterwards. This helps support your body’s recovery, restore your muscles and replace lost glycogen.

If you can’t eat straight away, or a full meal seems too much, go for a snack to tide you over and try to eat within a couple of hours.

What are the best foods to eat before exercising?

The best foods to eat ahead of your exercise session really depend on how far in advance you’re eating. Here’s an idea of what and how much to eat at different intervals.

Hours before your workout

If you’re loading up a few hours before your workout, go for foods that are high in carbs and low in fat, like pasta, rice, bread or cereal. Ideally, choose wholegrain varieties like wholemeal bread and pasta, brown rice or oats, as these provide a more sustained energy release.

You can afford to enjoy a whole pre-workout meal if you’re eating hours beforehand, as your body will have adequate time to digest it.

30 minutes before your workout

Only got 30 minutes? You’ll want to opt for a healthy snack, but it can be one that’s a bit more substantial.

You could go for a piece of (wholemeal) toast with peanut or almond butter, hummus with a few carrot sticks, a smoothie, or a small chia pudding.

You can also select your snack according to your workout. If you’re going for a jog or doing some other kind of cardio, choose something higher in carbs to deliver more energy to your muscles — like a small fruit salad or toast.

If you’re doing weights, increase your protein intake to support muscle building. You might want to go for a protein or meal replacement shake, a couple of boiled eggs, or some plain yoghurt with a handful of nuts.

Juniper's Nourish Shakes are a good option as they contain 29.4g of high-quality protein and 20 vitamins and minerals. These meal-replacement shakes help support your weight loss journey and keep you feeling fuller for longer.

10-15 minutes before your workout

If you’re short on time, you can still eat something but ensure it’s small and contains easily digestible carbs so you’re not uncomfortable during your workout. Consider a handful of berries, a banana, or an apple.

After your workout

A balanced meal with carbs and protein is best here. Your body needs both to restore glycogen levels, build new muscle, repair existing muscle and recover from your workout. Include healthy fats, too, to up the nutrition factor — think avocado, olive oil or raw nuts.

Meal ideas include lean meat (like chicken or turkey) with rice and veggies, in a wrap or on a sandwich, an omelette with toast, a bowl of porridge with fruit and nuts, or a grain salad with some kind of lean protein.

Make sure to drink plenty of H20

Regardless of what and when you eat, one thing that should always remain constant is your water consumption. This is to ensure you don’t become dehydrated when you exercise.

Aim for 2-3 cups of water before you work out, up to 1 cup of water every 15-20 minutes while you’re exercising, and 1-3 cups afterwards — or more if you sweat a lot [5].

If you're doing a lengthy session, you can also hydrate with a sports drink.

When should you exercise after eating if you want to lose weight?

What about if you’re trying to lose weight? Should you follow the same rules around what and when to eat? Again, it comes down to how much exercise you’re doing and what time of day you’re doing it.

If you’re getting up early to go for a walk, you could have a light snack or not eat at all. As we know, some research has shown that exercising while fasting can improve your body’s utilisation of fat tissue during a workout, leading to weight loss [3].

Plus, a 2015 Japanese study found that exercising before breakfast helped participants burn more fat in the following 24 hours compared to when they exercised in the afternoon or evening [6].

But if you’re doing higher-intensity exercise or weight training, fuelling up before your workout can sustain your energy and help you get the most out of your session.

It’s also worth remembering that the link between nutrition and exercise is often a very individual thing, which is why it can be useful to have someone supporting you with both.

Consider jumping on board a weight loss program, like Juniper’s Weight Reset Programme, where you’ll have access to health coaching to help you figure out your optimal diet and exercise plan. 

With a bit of extra support, you’ll be able to establish a regimen that suits your needs and your goals — taking all the guesswork out of exercise, what to eat and when.