Be warned – effective carb cycling requires strict tracking and plenty of planning ahead.
Medically reviewed by Dr Louise Wiseman MBBS, BSc (Hons), DRCOG, MRCGP and words by Annie Hayes
Hang around the gym locker room long enough and you’ll likely hear someone talking about carbohydrate cycling. The latest sports nutrition tactic to find favour with everyday athletes, carb cycling involves boosting your carb intake on some days (or weeks, or months) and cutting back on others.
It sounds straightforward on paper, but carb cycling requires plenty of number-crunching to figure out your individual needs. We asked Dan Price, sports nutritionist and head of nutrition at SIX3NINE Personal Training and Emily Servante, personal trainer at Ultimate Performance Kensington, to talk us through the dos and don’ts of carb cycling:
What is carb cycling?
Carb cycling involves alternating through phases of low-carb and high-carb consumption. ‘It refers to nutrition plans that have different carbohydrate intakes across different days, typically low, medium and high,’ says Price. ‘This cycle may exist over a week, two weeks or a longer period.’ By cutting carbs on certain days, you force your body to burn fat for fuel.
Sounds simple, right? In theory, yes. But in practice, effective carb cycling requires strict tracking and plenty of planning ahead. Unless you’re superhuman – or a nutritionist – you’re unlikely to know the carbohydrate content of every food item off the top of your head, so you’ll have to tally your intake and tailor it to your pre-determined requirements.
For that reason, carb cycling is unlikely to be something you want to use year-round. But if you have a specific fitness goal – to overcome a weight loss plateau, gain lean muscle, or fine-tune your physical performance – taking a targeted approach to your carbohydrate intake can give you a welcome boost.
How does carb cycling work?
Carb cycling usually revolves around a person’s training, with high-carb days reserved for intense training days, and low-carb days designated to rest periods, although other carb cycling schedules include:
- Strategic body composition, for example ‘cutting’ and ‘bulking’ periods.
- Refeeds, whereby you pre-determine high-carb days during a prolonged diet.
- Competitions and events, for example carb-loading before a marathon.
- Training type, whereby you eat according to the intensity and duration of individual sessions.
- Body fat levels, whereby you cycle your carbs in line with your measurements.
Typically, the low-carb phase omits starchy, complex or simple carbs to focus on protein, fat, and high-fibre fruit and vegetables, says Servante. What is considered a ‘medium’ or ‘high’ carbohydrate level varies from person to person, according to:
- Your age, weight and height
- Your basal metabolic rate (BMR)
- Your activity level
- Your daily macronutrient breakdown
Carb cycling isn’t necessarily about consuming fewer carbohydrates, says Price, but making better use of them. For example, instead of eating 95g of carbs every day for a week (totalling 665g), a person might divide them across two ‘high’ days (185g carbs), two ‘medium’ days (95g carbs) and three ‘low’ days (35g carbs). ‘You’re still consuming the same amount of carbohydrates,’ he says, ‘they’re just split up differently across the weekdays. The advantage of this approach is you get more carbs when you need them.’
Of course, on the days you’re eating fewer carbs, you’re also eating fewer overall calories. For that reason, you might also choose to cycle fats at the same time. ‘In order for calorie intake to stay stable alongside cycling levels of carbs, fat intake also has to be cycled,’ says Price. ‘This means on days when carbs are lower, fats are higher and vice versa. This approach keeps calorie intake stable across the week, but allows you to enjoy a more balanced diet with higher fat intake on rest days and a little more performance-focused carb-loading around those tough squat sessions.’
The benefits of carb cycling
Before we talk about the benefits of carb cycling, let’s make one thing clear: Carbs are not the enemy, far from it. ‘Carbohydrates are a vital fuel source for your brain and nervous system, as well as other organs, such as the kidneys,’ says Servante, and a source of gut-healthy fibre.
Carbs are also crucial for refuelling your muscles, boosting your metabolism, and enhancing your athletic performance. They improve your sleep, boost your mood, and regulate the function of appetite hormones (specifically leptin, which instructs your brain to feel full, and ghrelin, the hormone that signals hunger).
Carbohydrates are a vital fuel source for your brain and nervous system, as well as other organs.
So, why focus on carbs, and not proteins or fats? ‘Proteins and fats are an essential component of your diet, so these nutrients should be kept relatively constant throughout the week to make sure your daily requirements are met,’ says Price.
‘Carbohydrates are far less essential – diets can remain nutritionally complete with both low and high carbohydrate intakes.’ For that reason, he explains, they’re ‘a sensible variable to be adjusted up or down when looking to increase or decrease calorie intake for the purposes of fat loss and muscle gain’.
High-carb days keep your muscle glycogen topped up, helping to improve your athletic performance and prevent muscle breakdown – without sufficient carbs, your body starts burning muscle for energy, rather than fat, as Servante explains. ‘If we don’t give our body enough energy to perform the tasks we ask of it, the body must create fuel,’ she says. ‘It starts the process of gluconeogenesis; catabolising hard-earned muscle rather than tapping into your fat stores, which is the opposite of what most people want to happen.’
Eating carbs post-workout ‘raises insulin more quickly, so protein reaches cells sooner and muscle protein synthesis can start,’ says Servante. In short, that means faster recovery and improved ‘insulin sensitivity’. This means your cells use blood glucose more effectively, reducing your blood sugar levels. Having too much sugar in the blood for long periods of time increases your risk of serious health problems, such as heart disease, stroke, and kidney disease.
The low-carb days, meanwhile, switch your body over to a mostly fat-based energy system, improving what’s known as ‘metabolic flexibility’ to boost your ability to burn fat for fuel. ‘The purpose behind carb cycling is that it allows you to stay relatively low-carb most of the time, but increase your carbohydrate intake on certain days, so that you can reap all the benefits of without having to eat higher amounts all the time,’ says Servante.
Is carb cycling good for weight loss?
In theory, carb cycling is good for weight loss. Carb cycling allows you to tap into the benefits of a low-carb diet while fuelling your workouts – so you build more muscle, improve your fitness, and burn more calories. However, you’ll still only lose weight if you’re in a calorie deficit.
Energy balance determines whether you gain or lose weight, not where the calories come from.
‘It’s your energy balance overall that determines whether you maintain, gain or lose weight, not where those calories come from,’ says Servante. ‘You could eat 1,000 calories a day entirely from carbs and still lose weight, as long as you’re in a calorie deficit. Likewise, you could eat a high-fat-low-carb diet and gain weight if that put you in a calorie surplus – avocados have calories too.’
Put simply, ‘the level of calorie deficit you create determines whether and how much weight you lose,’ she adds. ‘The make-up of those calories and the type of training you do determines where that weight is lost from.’
What foods can you eat when carb cycling?
During a high-carb phase, you should focus on the following healthy carbohydrates:
- Whole grain complex carbohydrates such as brown rice, oats and quinoa.
- Slow-digesting legumes such as chickpeas, lentils and black beans
- Fibre-rich veggies such as carrots, sweet potatoes and peas.
Whether you’re in a high, medium or low-carb phase, always include plenty of low-carb vegetables such as broccoli, spinach, kale, courgettes, asparagus, mushrooms, cucumber, bell peppers, tomatoes, and so on.
How to do carb cycling
If you’re carb cycling for athletic performance, allocate high-carb days to your toughest training sessions. ‘This maximises your available energy for when you need it most, and can aid in speeding up recovery,’ says Price. ‘Medium-carb days may be better suited to lower intensity training days such as cardio or lighter resistance training, while low days can be kept to your rest days.’
If you’re carb cycling for weight loss, you might choose to cycle your carb intake around your social life. ‘This might look like low and medium days throughout the week and your two high days on the weekend,’ says Price. ‘While this is not going to give you the performance edge in your training during the week, it may be a great strategy for making your diet fit your lifestyle.’
Alternatively, you could follow a predominantly low-carb diet, and schedule in high-carb ‘re-feeds’ – for example, a four-week low-carb phase followed by a one week re-feed. Regardless of which method you choose, you’ll need to experiment with both the amount of high-carb days you incorporate and the amount of carbs you consume to find your personal sweet spot – not just for your goals, but for your lifestyle and workout regimen, too.
The risks of carb cycling
Carb cycling can be a useful tool to break through a training or weight loss plateau, but it isn’t suitable for everyone – for example, people with eating disorders, diabetes or heart disease, or for pregnant or nursing mothers.
Additionally, the low-carb phase of the diet can cause side effects such as fatigue, bloating, irritability, constipation and problems sleeping. Carb cycling can also be extremely mentally taxing. It’s very strict and time-consuming, because you have to plan, prep and track everything you eat and drink, so proceed with caution.
It is important to be aware that long-term data is not yet available regarding the benefits.
‘Carb cycling is an extreme example of food planning and it is important to be aware that long-term data is not yet available regarding the benefits or disadvantages of carb cycling on the body’s biological parameters such as cholesterol, blood sugar measures, blood pressure etc,’ warns Dr Louise Wiseman.
‘Focussing on healthy food is vital and a balance of all food groups and vitamins and minerals are essential for long term health,’ she adds. ‘Always consult with your doctor before considering an extreme change of lifestyle.’