When it comes down to people’s opinions on carbohydrate intake and fat loss, they usually have a lot in common with assholes. Everybody has one, but quite often they are full of shit. 

It seems as though now more than ever, that the nutritional equation being perpetuated in mainstream media is: eating carbs causes fat storage, therefore carbs must be evil and should be avoided. However the fact of the matter is that fat gain has more to do with energy balance, and eating TOO MUCH of the WRONG TYPE of carbs, at the WRONG time. 

carb cycling for fat loss


Due to the popularity of low carb diet camps such as The Atkins Diet, Ketogenic and the Paleo/Primal Movement, public awareness of the benefit of eating low carb for losing fat is now centre stage. And although carb cycling sounds rather complex, it is actually one of the simplest and widely utilised nutritional strategies for building muscle and stripping body fat fast! 


  • Fat loss
  • Maintain lean muscle mass
  • Improved insulin response
  • Improved leptin signalling

Simply put, carb cycling involves manipulating your daily carbohydrate intake by rotation of low, moderate and/or high carb days. You can then step things up a gear by undulating your daily caloric intake, whether it be high or low. 

For example, as part of a fat loss plan you would establish a caloric deficit, with lower calories on rest days. As opposed to strategically planning a re-feed/refuel day, where replenishment of muscle glycogen is the goal and overall calories are much higher.

The chief reason carb cycling plays such a pivotal role in so many fat loss success stories, is how it allows you to harness the awesome power of insulin and have it work for you – instead of against you. 

Insulin is the hormone that acts as the ‘key’ to the ‘door’ of your cells. It allows glucose to be absorbed from the bloodstream either into your cells to fuel them, or adipose tissue. Now if you have been on a relatively high carbohydrate diet for some time, it is highly probable that you will already be predisposed to some degree of insulin resistance. This occurs when your cells remain ‘locked’ in the presence of insulin, causing a build up of glucose in the bloodstream and dramatic increase in fat storage as a result. Quite often a key indicator of insulin resistance is accumulation of fat on the abdomen, hips and lower back, commonly referred to as the ‘spare tyre’ syndrome. The main takeaway here is that insulin is a major player in the fat loss game, and carb cycling remains one of the most effective means to increase insulin sensitivity, stabilise blood sugar levels and hit the ground running.

Whilst on the topic of hormones, Leptin is another hormone that deserves a mention, as insulin resistance and leptin resistance often go hand in hand. Leptin is secreted by fat cells and is received by receptors in the hypothalamus. It stabilises our weight by means of regulating energy balance and influencing our brains feelings of hunger and satiety. More or less, leptin levels are your body talking to your brain telling you whether you are satiated or starving. Therefore an obese person with higher leptin levels has increased appetite. The solution? Fat loss resulting in lower leptin levels = improved hunger signalling and energy balance is restored. Ah! Homeostasis indeed is a truly magical thing!

Lastly, it is a well-known fact, that muscle is the most metabolically active tissue in the body and is often shed during periods of dieting and caloric restriction. Through planned re-feeds, carb cycling allows for a certain level of metabolic flexibility, as you can maintain a caloric deficit for longer whilst preventing muscle loss and metabolic down regulation. 

In contrast, carb cycling may be beneficial for those already with a sluggish metabolism due to a history of crash dieting or chronic under-eating. In this instance, carb cycling can be ideal for ramping up metabolism and prevent fat gain, by slowly ‘reverse dieting.’ This involves bringing total calories back up to a dietary baseline, by gently undulating caloric/carbohydrate intake.


What makes carb cycling so darn user friendly, is that it is such a flexible approach to nutritional planning. However it’s application is dictated by the outcome intended. However, carb cycling can be broken down into 2 types.

FREQUENT REFEEDS: Typically consists of an undulating system of high, moderate to low carb days within a small window of time, such as week to week.

Frequent Refeed Carb cycle

This approach is excellent for promoting muscle growth and recovery, as the higher carbohydrate days are prioritised on the days the trainee is doing either high volume work, or specialising in a muscle group. This allows muscle glycogen to be replenished to help boost performance in the gym, as well as minimise fat storage. 

In terms of client compliance, this model would be more sustainable, yet depending on your client; you could be as generous or restrictive as desired.

INFREQUENT REFEEDS: Low carb periods tend to span longer periods of time, accompanied by glycogen depletion and carb refuelling well above what would be normally eaten on your standard high carb day. 

Long-term carb cycling models with infrequent re-feeds as described above, are quite common amongst fitness competitors during depletion phases, or individuals who are extremely insulin resistant. 


So what’s the catch? Well, cutting carbs can come at a cost, and biochemical individuality dictates that it really comes down to your genetics as to how you will respond. In the absence of carbs some people positively thrive; whilst others fall apart at the seams. 

So before you dive in, there are a few things you will fare well to know – otherwise you may end up paying the piper dearly.


Weight training, such as high reps and metabolic circuit training, combined with low carb eating will result in quickening of fatigue and loss in performance due to the depletion of muscle glycogen stores. This is usually what people when training refer to as ‘hitting the wall.’ 


Your brain’s preferred fuel source is glucose; therefore carb deprivation can coincide with brain fog, dizziness, mood swings and irritability. 

Resilience to stress can also be compromised, elevating levels of the stress hormone cortisol. Cortisol is a catabolic hormone, and tears down muscle tissue for the amino acids to convert to glucose in the liver via gluconeogenesis. Interrupted sleeping patterns also come with the territory, which in turn causes fatigue, which in turn raises cortisol in an out of control downward spiral. If you have a client who is highly stressed, then severely limiting carbohydrate intake is a sure-fire recipe for adrenal burnout. 


One of the first things to go in a low carb diet is grains, yet grains are a common source of prebiotic fibre for feeding our gut flora. Certain strains of good bacteria in the gut rely on constant intake of fibre and resistant starch, through the diet, as food. Imbalances in gut bacteria drastically affect digestion, mood and immune function on a global scale. 

As a work around, one strategy is to try incorporating raw unmodified potato starch and/or green banana flour into your diet, to help support gut health and the balance of good bacteria.

Carbohydrates also provide the fuel for production of serotonin (the ‘happy’ neurotransmitter) in the gut. When depleted, low serotonin is also linked to depression, anxiety and disrupted sleep patterns. 


Research suggests that glucose is the intermediary that regulates thyroid function. Subsequently, long-term restriction of carbohydrates can result in a drop of the bodies’ conversion of the inactive form of thyroid hormone Thyroxine (T4) to its active form, triiodothyronine (T3). The thyroid gland is best likened to the thermostat in your home that’s job is to regulate your body temperature and overall metabolism. Lowered T3 levels can result in a depressed metabolism and impaired muscle protein synthesis. 

One study published in The Journal of Clinical Endocrinology & Metabolism investigated the hormonal implications of fasting and carbohydrate restriction in obese subjects. Subjects who were receiving a daily intake of at least 50g of carbohydrate per day on a calorically restricted diet over a 2-week period, showed no significant drops in T3 levels. Which is why adequate re-feeds are so important!


In the absence of glucose, there is also the ever-present risk of muscle loss as the body tries to balance its blood sugar levels. 

With a drop in blood sugar, you body begins cannibalising muscle tissue, to break it down into amino acids to be sent to the liver. From there, those amino acids are converted to glucose through a process called gluconeogenesis. As touched upon earlier, elevations in cortisol will also drive gluconeogenesis. 


Although in the medical literature ketogenic diets have been proven successful in treating certain conditions such as epilepsy, people with certain medical conditions may be less well off. 

An example of which is diabetic ketoacidosis. A condition that affects people with type 1 diabetes, and sets in when glucose is scarce, and the breakdown of fat produce ketones in the bloodstream, to rise to dangerously high levels compromising the heart, brain and kidneys.  


All things aside, the make or break of any nutrition plan is always going to be the degree to which a client is willing to comply. If you or a client has not gone a day without carbs since Neil Armstrong set foot on the moon, then you are going to have a hard time getting them all ‘gung-ho!’ about giving them up entirely. 

This is where making the effort to understand your client inside out, from their physiology to their psychology, is crucial to being able to guide them to create REAL change. 


‘You have got to deserve your carbs.’ – Charles R. Poliquin

As human beings, by nature we tend to always do things in extremes. Now don’t get me wrong, this is not to say that carb cycling is an extreme measure by any means. As by now I’m sure you will agree it actually makes absolute perfect sense to control and undulate carb intake in a responsible manner. 

But in saying that, whether it be physically or mentally, wiping ALL clean carbs off the menu entirely for days at a time simply may not be the best option for everyone. At the end of the day, carb cycling is but one nutritional strategy of which there are countless others. In theory they all technically work, but the only true measure of success of any system is gauged in it’s careful planning, execution and the human cost of which, should be scrutinized as to what is actually best for the individual concerned.


  • Volek JS, Sharman MJ, Love DM: Body composition and hormonal responses to a carbohydrate-restricted diet. Metabolism. 2002, 51: 864-870. 10.1053/meta.2002.32037.
  • Luigi Fontana, Samuel Klein, John O. Holloszy, and Bhartur N. Premachandra: Effect of Long-Term Calorie Restriction with Adequate Protein and Micronutrients on Thyroid Hormones. The Journal of Clinical Endocrinology & Metabolism. 2011. DOI: http://dx.doi.org/10.1210/jc.2006-0328
  • Spaulding SW, Chopra IJ, Sherwin RS, Lyall SS: Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man. J Clin Endocrinol Metab. 1976 Jan;42(1):197-200. DOI: 10.1210/jcem-42-1-197
  • Anssi H Manninen: Metabolic Effects of the Very-Low-Carbohydrate Diets: Misunderstood "Villains" of Human Metabolism. Journal of the International Society of Sports Nutrition20041:7. DOI: 10.1186/1550-2783-1-2-7



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