Carbohydrates are one of the most misunderstood nutrients we eat. They’ve become the villain of countless diet trends, yet they’re also your body’s preferred source of energy – especially when you’re training.
From powering your F45 workouts to fueling brain function and recovery, carbs play a vital role in everyday health. The goal isn’t to avoid them, but instead to understand which types of carbohydrates to reach for – and when. With that in mind, read on. In this guide, we’ll break down what carbohydrates are, how they work, the different types, and how to integrate this key macronutrient into both a balanced diet and a sustainable workout routine.
What are carbohydrates?
Carbohydrates – or, simply, “carbs” – are one of the three macronutrients your body needs in large amounts, alongside protein and fat.1
When you eat carbohydrates, your digestive system breaks most of them down into glucose. This glucose enters your bloodstream, where it can be used immediately for energy. Whatever you don’t need right now is stored as glycogen in your muscles and liver, waiting to be called on later.1
During high-intensity exercise like an F45 workout, your body turns to that stored glycogen to power your movement. It’s quick to access and fast to convert – exactly what you need when you’re working hard.2
What do carbohydrates do in the body?
Eating different types of carbohydrates means your body can:
- Sustain lasting energy3 – your body draws on glucose all day to keep everything running, from your heartbeat to your next step.
- Support healthy digestion3 – fiber-rich carbs like whole grains and vegetables keep things moving through your gut and feed the good bacteria living there.
- Power your training3 – when you push into a sprint or a heavy set, your body reaches for glucose to fuel those fast, explosive efforts.
- Sharpen your mind3 – your brain runs almost entirely on glucose, so a steady supply keeps your focus and memory switched on.
- Speed up recovery3 – carbs help replace the glycogen your muscles burn through in a session, so you bounce back ready for the next one.
What are the different types of carbohydrates?
Carbohydrates are commonly grouped into three types – simple carbohydrates, complex carbohydrates, and fiber4 – and each behaves differently.
Below, we break down how these different types of carbohydrates work.
What are simple carbohydrates?
Simple carbohydrates – also known as ‘simple sugars’ – consist of one or two sugar molecules, allowing your body to digest and absorb them relatively quickly. This makes them a rapid source of energy.4
It’s a common misconception that all simple carbs are ‘bad’. Plenty of nutritious foods contain them naturally: including fruit, milk, and honey. That said, simple carbs also show up as added sugars in products like candy, sodas, and baked goods – and when these are eaten regularly, without any protein or fiber to slow things down, the repeated glucose spikes can contribute to repeated sugar cravings.
What are complex carbohydrates?
Complex carbohydrates are built from longer chains of sugar molecules, so they take more time to break down – especially when they come from minimally processed, fiber-rich foods. That slower breakdown gives you a steadier release of energy and helps you feel satisfied for longer between meals.4
Because they release energy so evenly, complex carbs are worth building into your regular daily meals rather than saving for one sitting. Nutritious sources include oats, brown rice, whole grain bread, sweet potato, and quinoa.
What is fiber?
Fiber is also a type of carbohydrate, but unlike simple and complex carbs your body doesn’t fully digest it in the small intestine.
Instead, it travels further through your digestive system, where different forms of fiber encourage a diverse gut microbiome – which in turn aids your digestion, keeps you feeling satisfied, and helps fend off harmful bacteria to support your immune system.4
You’ll find fiber naturally in plant foods like fruit, vegetables, legumes, whole grains, nuts and seeds.
Why carbohydrates are important for exercise
When you take on high-intensity exercise – like our resistance, cardio, and hybrid workouts here at F45 – your VO2 – the amount of oxygen your body takes in and uses during exercise – increases as the intensity of the workout does.
VO2 max is the maximum amount it can use. Once you’re working at around 80% of your VO2 max, carbohydrates become your body’s main fuel source, taking over from the greater proportion of fat used at lower intensities.5
This means the carbs you’ve eaten are now doing the heavy lifting: fueling every rep, sprint, and lift through to the end of your session.
When we asked F45 athlete and trainer Jess Bell what carbohydrates do for your performance, she told us: “I avoid training on an empty stomach if I can. I’ll usually have a proper meal built around complex carbs and whole foods beforehand. But for early morning sessions, when my appetite isn’t really there yet, I’ll still grab something easy to digest like an apple or a nutrition bar to give me the quick burst of energy I need.”
What are the best carbohydrate foods for active people?
Instead of asking “what foods are high in carbohydrates?”, try asking “will this fuel me and feed my body well?” Well, the best carbs do – giving you lasting energy while delivering fiber, vitamins, and minerals your body can use.
Below are some great options that tick both boxes.
Whole grains
Whole grains are a reliable, everyday source of steady energy, and they bring fiber to the table too. Brown rice, whole-grain pasta, and oats are all easy staples to keep on high rotation.
Fruit
Fruit delivers natural sugars for accessible energy, along with fiber to slow things down and a generous hit of vitamins. It’s proof that “simple” carbs can absolutely be part of a well-fueled diet – and not a bad snack to eat before or after your workout, either!
Starchy vegetables
Starchy vegetables are a satisfying, nutrient-rich way to top up your carbohydrate intake. Sweet potato, potato, pumpkin, and corn all fit the bill, and they’re endlessly versatile across meals. They’re also easy to meal prep for the week – simply roast a big tray at the start of the week and you’ve got a ready-made carb base to build into lunches and dinners.
Legumes
Lentils, garbanzo beans, and peas combine carbohydrates, fiber, and plant-based protein, and digest slowly for steady, lasting fullness – which makes them a smart pick if you’re eating within a shorter window (for example, if you’re intermittent fasting). Add them to soups, curries, salads, or wraps to make a meal more substantial.
Common myths about carbohydrates
Now you understand what carbs are, it’s time to put a few common myths to bed. Read on as we debunk some of the most persistent rumors about your body’s main source of energy.
“Carbs make you gain weight.”
Carbs and calories aren’t the same thing. Calories are simply a unit of energy your body gets from food, while carbs are just one of three nutrients that supply them. Weight gain happens when your total daily calories exceed what your body burns – whether those calories come from carbs, fats, or protein.6
“Low-carb diets are best for everyone.”
There’s no single diet that fits everyone. We all have different builds, activity levels, and metabolisms – so, while a low-carb approach can work well for some people as part of a holistic weight loss plan, others thrive on a very different balance of foods.7
For those with a carbohydrate intolerance, where the body has trouble digesting certain carbs, cutting back may bring real benefits.
“You shouldn’t eat carbs at night.”
Your total calorie balance doesn’t know what time it is – so a late meal isn’t the problem it’s made out to be.
In fact, complex carbs eaten a few hours before bed are among the foods that help you sleep, as they can help your body’s production of sleep-promoting hormones like serotonin and melatonin8. Just be mindful of indulging in too many late-night sweet cravings!
Understanding the different types of carbohydrates can help you make informed choices to support your diet and fitness goals. Ready to put that energy to work? Find your nearest F45 studio and start training with us.
1 https://pubmed.ncbi.nlm.nih.gov/29083823/
2 https://pmc.ncbi.nlm.nih.gov/articles/PMC5794245/
3 https://www.betterhealth.vic.gov.au/health/healthyliving/carbohydrates-and-the-glycaemic-index
4 https://my.clevelandclinic.org/health/articles/15416-carbohydrates
5 https://pmc.ncbi.nlm.nih.gov/articles/PMC5766985/
6 https://www.fda.gov/food/nutrition-facts-label/calories-nutrition-facts-label
