Carb-Cycling for Fat Loss
Carb cycling is a dietary strategy that involves alternating high-carbohydrate days with medium and low-carbohydrate days. It is often used as a weight loss, fat loss or bodybuilding tool.
The idea is that on high-carbohydrate days, your body will have enough carbohydrates to fuel your workouts and support muscle growth, while on low-carbohydrate days, your body will be forced to burn body fat and dietary intake of protein and fat for energy.
Carb cycling can be beneficial for fat loss because it can help regulate insulin levels and improve insulin sensitivity, which can reduce body fat. Additionally, cycling carbohydrates can help prevent metabolic adaptation and plateaus in weight loss by keeping the body guessing and preventing it from getting used to a particular diet.
Carb cycling can also be helpful for athletes who need to increase their carbohydrate intake for performance on certain days while still maintaining a calorie deficit for weight loss.
It is important to know it will not be suitable for everyone and should be undertaken with guidance from a qualified practitioner.
What’s going on?
The glycolytic pathway and gluconeogenesis are both metabolic pathways involved in the production of glucose, but they have opposite functions.
The glycolytic pathway is a catabolic pathway that breaks down glucose to produce energy, while gluconeogenesis is an anabolic pathway that synthesises glucose from non-carbohydrate sources.
Shown below we can see the pro- and preceding functions of these two pathways.
Simply put, our bodies use sugar, if we don't eat it, we make it by breaking down our own fatty acids and protein (body fat, circulating fat or muscle protein) or from dietary sources.
Therefore, it is an expensive pathway in the body to use fat and protein, it costs you to fuel you.
*image found at: https://step1.medbullets.com/biochemistry/102052/gluconeogenesis
Differences between the glycolytic pathway and gluconeogenesis:
The glycolytic pathway proceeds in the direction of glucose breakdown, while gluconeogenesis proceeds in the opposite direction to produce glucose.
The glycolytic pathway generates energy (ATP) by breaking down glucose, while gluconeogenesis requires energy (ATP) to synthesise glucose.
The glycolytic pathway uses glucose as its substrate, while gluconeogenesis uses non-carbohydrate sources like pyruvate, lactate, and amino acids.
The enzymes involved in the glycolytic pathway and gluconeogenesis are different, although some enzymes are shared between the two pathways. For example, pyruvate kinase is used in the glycolytic pathway to convert phosphoenolpyruvate to pyruvate, while during gluconeogenesis, the reaction is catalysed by pyruvate carboxylase and phosphoenolpyruvate carboxykinase.
The glycolytic pathway is regulated by the availability of glucose and the energy needs of the cell, while gluconeogenesis is regulated by hormones like glucagon and insulin.
In summary:
The glycolytic pathway is a catabolic process that breaks down glucose to produce energy, while gluconeogenesis is an anabolic process that synthesises glucose from non-carbohydrate sources.
Water Balance
Protein and carbohydrates can have different effects on water balance in the body due to their differences in chemical structure and metabolism.
Protein:
Protein is made up of amino acids, which contain nitrogen.
When protein is metabolised, nitrogen is excreted through the kidneys in the form of urea. Urea requires water to be excreted from the body, so the more protein consumed, the more water is needed to excrete the urea.
This can lead to increased urine output and water loss, which can contribute to dehydration if fluid and salt intake is not increased to compensate for the extra water loss.
Carbohydrates:
Carbohydrates are broken down into glucose, which is used by the body for energy or stored as glycogen in the liver and muscles.
Glycogen is stored with water, so when glycogen is broken down to release glucose, the water is also released.
This can lead to an increase in water retention and hydration in the body.
Overall, both protein and carbohydrates can have an impact on water balance in the body, but the effects are different.
We can see a great shift in body weight when utilising carb-cycling but also this means we need different levels of hydration.
Hormones
Carb cycling can have different effects on hormones depending on the specific details of the protocol and individual factors. Carb cycling is generally designed to manipulate insulin levels, which can in turn affect other hormones and promote fat loss.
The impact of carb cycling on hormones such as testosterone, estrogen, cortisol, thyroid, and insulin can vary depending on the specific details of the carb cycling protocol, as well as individual factors such as age, sex, and health status.
Testosterone:
Testosterone is an important hormone for muscle growth and development.
Some studies suggest that a diet high in carbohydrates may reduce testosterone levels, while a low-carbohydrate diet may increase testosterone levels.
When dietary carbohydrates are low, protein and fat usage are elevated.
However, the impact of carb cycling on testosterone levels is not well-established, and more research is needed.
Estrogen:
Estrogen is a hormone that plays a key role in reproductive health, bone density, and cardiovascular health.
Some research suggests that a diet high in carbohydrates may increase estrogen levels, while a low-carbohydrate diet may reduce estrogen levels.
When dietary carbohydrate goes up, estrogen and insulin elevate, inversely as dietary carbohydrates come down.
However, the impact of carb cycling on estrogen levels is not well-established, and more research is needed.
Cortisol:
Cortisol is a catabolic hormone that is released in response to stress and can contribute to the breakdown of tissue.
Some studies suggest that a low-carbohydrate diet may increase cortisol levels, while a high-carbohydrate diet may reduce cortisol levels.
On low-carbohydrate days, cortisol levels may be elevated due to the stress of glycogen depletion and increased reliance on fat for fuel. However, over time, you adapt and become more efficient at using fat as fuel, which can reduce cortisol levels and promote fat loss.
However, the impact of carb cycling on cortisol levels is not well-established, and more research is needed.
Thyroid:
The thyroid gland produces hormones that regulate metabolism and energy expenditure.
Some research suggests that a low-carbohydrate diet may reduce thyroid hormone levels, while a high-carbohydrate diet may increase thyroid hormone levels.
On low-carbohydrate days, thyroid hormone levels may be reduced due to the stress of glycogen depletion and carbohydrate intake.
However, over time, the body will adapt and regulate itself.
Insulin:
Insulin is an anabolic hormone that regulates blood sugar levels and promotes blood sugar and nutrient storage.
This is the only hormone that you actually have any kind of control over, by movement and what you put into your mouth.
Carb cycling is designed to manipulate insulin levels by alternating between high-carbohydrate and low-carbohydrate days.
On high-carbohydrate days, insulin levels are expected to be higher, while on low-carbohydrate days, insulin levels are expected to be lower.