From high-carb to low-carb diets, and everything in between, individuals are searching for sustainable and effective solutions.
One of the biggest dilemmas people face when trying to lose weight is choosing between a long-lasting or quick-acting diet, but the wrong choice can make it challenging to keep the weight off in the long run.
Two of the most discussed dietary approaches in recent times are the carb cycling diet and ketogenic (keto) cycling. Both have gained substantial attention for their potential in promoting weight loss. However, as with any diet, they come with their respective benefits and challenges.
We turned to Lumen nutritionists and metabolism experts to explain the pros and cons of each nutrition approach and surface the considerations for each.
"Many people believe that adopting a healthy lifestyle means cutting out carbohydrates," shares Abigail Markman, nutritionist at Lumen. "However, confining ourselves to these carb-restrictive diets for prolonged periods might compromise our metabolic flexibility and actually prevent us from reaching our health goals." "This might also explain peoples' interests shifting from rigid no-carb diets like Keto in the past years to sustainable alternatives like Carb Cycling," Abigail adds.
So, what are their merits and downsides? While keto can be highly effective for quick weight loss, some might find themselves stuck due to various reasons, such as restrictions and sustainability (1). However, carb cycling between low, medium, and high-carb days according to your metabolic needs, efficiently leads to better metabolic flexibility, healthy benefits, and sustainable well-being over time.
Take the metabolic health assessment to personalize your nutrition plan according to your current metabolic flexibility.
Carb cycling is a dietary approach that involves alternating between high-carb and low-carb days rather than maintaining a constant carbohydrate intake. So, instead of eating the same amount of carbs every day, some days you eat more, and some days you eat less. This dynamic approach aligns with our body's metabolic processes, offering a tailored way to harness energy sources.
Why? Your body uses carbs and fats differently for energy.
Carbohydrates and fats are broken down through different metabolic pathways. Carbohydrates are broken down into glucose, which is then used for energy through glycolysis and the Krebs cycle.
Insulin helps to move glucose from the bloodstream into cells, where it can be used for energy. When insulin levels are high, the body is more likely to use carbohydrates for energy and less likely to use fats for energy.
Fats are broken down into fatty acids, which can be used for energy through beta-oxidation. Fats typically provide more than half of the body's energy needs. Carbs provide the rest of the body's energy needs, but they are more important for short-term energy needs, such as during exercise.
For example, on high-carb days, you're not just fueling workouts; you're also replenishing glycogen, the primary carbohydrate stored in muscles. Glycogen acts as a rapid energy reserve, especially during intense physical exertion when fast energy release is needed (2).
On low-carb days, the focus shifts. By reducing carbohydrate availability, the body breaks down its fat stores into energy through a process known as beta-oxidation (3).
Though athletes and those engaged in high-intensity training have long adopted carb cycling to match their rigorous energy demands, people looking for better ways to improve their metabolic health and weight management are turning to carb cycling. We'll explain why below.
Even for the general population, this carb strategy can provide benefits in weight management and metabolic health, by leveraging on the body's innate metabolic pathways.
Optimized Energy: Aligning carbohydrate intake with activity levels ensures the body gets the fuel it needs when it needs it.
Improved Weight Loss: Periodic carb reduction nudges your body to burn its stored fat, enhancing weight loss.
Enhanced Metabolic Flexibility: Alternating between high and low-carb days can improve the body's ability to shift between using carbs and fats as fuel sources seamlessly.
Maintained Muscle Mass: On high-carb days, the body has enough fuel to support intense workouts, helping in muscle building and retention.
Carb cycling fosters metabolic flexibility, which refers to the body's proficiency in alternating between carbohydrates and fat for energy generation. The science behind it is intriguing:
High-carb days: Here, the emphasis is on replenishing the body's glycogen reservoirs. When we consume carbohydrates, they are broken down into glucose, which is the body's preferred source of energy. Glucose enters the bloodstream and causes blood sugar levels to rise. The pancreas then releases insulin, a hormone that signals to cells to take up glucose from the blood.
Muscles are particularly sensitive to insulin, and they take up glucose very efficiently when insulin levels are high. This is because insulin helps to open up glucose transporters in muscle cells. This process of glucose uptake is known as glycogen synthesis.
Insulin also has a direct effect on muscle protein synthesis. Insulin helps to activate the mTOR pathway, which is a signaling pathway that is essential for muscle growth.
Therefore, consuming carbs after exercise can help to replenish glycogen stores in muscles, enhance glucose uptake by muscles, and boost insulin sensitivity, all of which are important for muscle growth.
Low-carb days: A reduced carb intake means glycogen stores run low and the body breaks down stored glycogen for energy. This depletion triggers a metabolic response, that increases the breakdown of stored triglycerides into free fatty acids for energy production.
Free fatty acids can be used by the body for energy production, even in the absence of carbs. This increase may also help to improve insulin sensitivity.
By manipulating insulin responses and tweaking metabolic rates in this cyclical manner, the body is positioned favorably for both fat reduction and muscle retention (5).
Low-carb diets have been associated with better sleep and cognitive health in a cross-sectional study from the Journal of Food Science & Nutrition (6). The study found that people who followed a low-carb diet were likelier to report good sleep quality and had better cognitive function than those who followed a high-carb diet.
A clinical study centered around Lumen’s methodology found that a carb cycling approach effectively enhances insulin sensitivity, paving the way for fat loss without compromising muscle bulk (Source 4).
People on a carb cycling meal plan eat different foods on different days, depending on their carb intake for that day.
High-carb days feature carbohydrate-rich foods such as:
Whole grains, such as oats, quinoa, and brown rice
Fruits and vegetables
Starchy vegetables, such as potatoes, corn, and peas
Legumes, such as beans, lentils, and peas
Low-carb days spotlight foods such as:
Meat and poultry
Fish and seafood
Non-starchy vegetables, such as leafy greens, broccoli, cauliflower, and zucchini
Healthy fats, such as olive oil, avocado oil, and nuts
The ketogenic diet is a low-carb, high-fat dietary pattern that steers the body into a metabolic state called ketosis. The diet consists mostly of fats (60-80% of total calories), moderate protein (15-20%), and low carbohydrates (5-10%). This macronutrient ratio transitions the body's metabolic state from glucose-dependence to one where fats become the primary energy source, promoting ketogenesis.
With decreased glucose availability from carbohydrates, the body uses stored fats to produce energy. The liver produces three main ketone bodies: beta-hydroxybutyrate, acetoacetate, and acetone. As fat oxidation increases due to low glucose availability, the liver converts fatty acids into ketone bodies to efficiently provide energy.
Most keto dieters now follow a standard keto diet, a low-carbohydrate, high-fat diet that allows for moderate protein intake.
Meat and poultry: Beef, chicken, turkey, pork, lamb, bacon, sausage, etc.
Fish and seafood: Salmon, tuna, sardines, mackerel, shrimp, shellfish, etc.
Eggs: Whole eggs, omelets, scrambled eggs, etc.
Healthy fats: Avocado oil, olive oil, coconut oil, butter, ghee, nuts, seeds, etc.
Low-carb vegetables: Leafy greens, broccoli, cauliflower, zucchini, asparagus, peppers, etc.
Full-fat dairy: Cheese, cream, yogurt, etc.
A peer-reviewed article outlines how ketogenic diets change the body's metabolic machinery to utilize fats as primary fuel, improving overall metabolic health (Source 5).
Another review in Nutrients shows that a ketogenic diet can help manage symptoms of metabolic syndrome, a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes (Source 6).
Every individual's body and metabolism are unique. What works wonders for one person might not be effective for another. Therefore, when choosing between carb cycling and the keto diet, consider the following:
Having to calculate your daily macros intake and meal prep on a daily basis while constantly needing to track your progress and performance can present real hurdles.
Personalized carb cycling planning can be a practical approach for achieving multiple goals like fat loss, muscle gain, metabolic function, and improved athletic performance. Plus, you will know what you need to eat and when.
Individualizing carb cycling is can significantly amplify its benefits. When carb intake is tailored to your metabolic rate (7), activity levels, and health goals, you're more likely to experience the benefits of optimized weight loss, better energy levels, and feeling healthier.
Keto or generic one-size-fits-all diets often miss the nuanced needs of an individual. This often leads to the cycle of yo-yo dieting and hitting plateaus because you need to feed your body what it needs when it needs it. When personalizing your carb cycling plan, you're giving yourself room to achieve greater metabolic flexibility and long-term success.
Remember, no diet can work in isolation. Both carb cycling and keto diets can deliver better results when combined with a balanced lifestyle that includes adequate sleep, regular exercise, and mental wellness.
Eat a variety of nutrient-rich foods, including fruits, vegetables, whole grains, lean protein, and healthy fats.
Focus on unprocessed or minimally processed foods.
Limit your intake of added sugars and unhealthy fats.
Make sure to stay hydrated.
Aim for at least 30 minutes of moderate-intensity exercise most days of the week.
Include a variety of workouts in your routine, such as cardio, strength training, and flexibility exercises.
Listen to your body and rest when you need to.
Aim for 7-8 hours of sleep per night.
Establish a regular sleep schedule and stick to it as much as possible.
Create a relaxing bedtime routine.
Make sure your bedroom is dark, quiet, and cool.
Find healthy ways to manage stress, such as exercise, yoga, or meditation.
Get regular social support.
Practice positive self-talk.
Following these tips, you can optimize your nutrition, workouts, sleep, and mind for carb cycling and keto diets. This will help you to achieve your goals and improve your overall health and well-being.
Lumen is a metabolic health tracker designed to provide real-time feedback on your metabolic state, making it easier than ever to understand your body's energy needs. Here's how Lumen can be a game-changer when it comes to carb cycling:
By analyzing your breath, you can determine whether your body is using fats or carbs for energy. This can guide you on when to cycle in higher-carb days or when to stick to low-carb days, depending on your metabolic state.
For instance, if Lumen indicates your body is primarily burning carbs, you might consider that day as a low-carb day to encourage your body to tap into fat stores.
Consistency is key when it comes to reaching your goals. Monitoring your fat-burning states over time can help you stick to your plan and see your progress. A data-driven approach can even reveal patterns that could help refine your dietary strategy if you hit any bumps in the road.
Instead of relying solely on a fixed meal plan, carb cycling based on real-time feedback can guide your dietary choices throughout the day.
If you're burning more fat in the morning, you might want to opt for a protein-packed breakfast. Alternatively, if you're using carbs as fuel after a workout, go for a carb-replenishing meal.
If you’d like to get a better handle on your progress and carb cycling, check out Lumen here.
Imagine you're using the Lumen device and app. After a morning workout, the app indicates you're primarily burning fat. This could be a cue to stick to a lower-carb, higher-fat meal for breakfast. Later in the day, after a carb-rich lunch, Lumen indicates a shift towards burning carbs. This real-time feedback can help you plan your dinner accordingly.
Getting started with either carb cycling or keto primarily involves planning your diet.
For carb cycling, you'll need to alternate between high, moderate, and low-carb days according to your workout intensity and health goals. With keto, you'll mostly consume fats, moderate proteins, and very low carbs.
In both approaches, it's beneficial to consult a healthcare provider or nutritionist to tailor the diet to your individual needs. Research supports the use of personalized dietary planning to enhance wellness goal achievement and overall health. (Source 7)
For carb cycling, the foods you should focus on vary depending on whether you're on a high-carb or low-carb day.
On high-carb days, aim for complex carbohydrates that are rich in fiber and nutrients, such as sweet potatoes, brown rice, quinoa, and whole-grain bread. These types of carbs are slower to digest and provide a sustained release of energy. A study published in Nutrients shows that high-fiber carbohydrates can improve metabolic health and help control body weight (Source 11).
On low-carb days, concentrate on consuming more fibrous vegetables like leafy greens, cauliflower, and bell peppers, along with lean proteins and healthy fats.
Both diets come with possible side effects. Carb cycling may cause mood swings or energy fluctuation due to carb variation.
The keto diet can lead to the "keto flu," a short-term group of symptoms including headache and fatigue. According to a review article published in 2020, transitioning into ketosis may also lead to micronutrient deficiencies if not properly managed. (Source 11)
The choice between carb cycling and keto depends on your personal health goals, lifestyle, and metabolic flexibility. While both can be beneficial, they come with their own sets of pros and cons.
Take our quiz to find out which approach—carb cycling or keto—is best suited for you. Also, learn more about how Lumen can personalize your metabolic health journey.
You might also be intrested in the below article:
1. Batch, J. T., Lamsal, S. P., Adkins, M., Sultan, S., & Ramirez, M. N. (2020). Advantages and Disadvantages of the Ketogenic Diet: A Review Article. Cureus, 12(8). https://doi.org/10.7759/cureus.9639
2. Jensen, J., Rustad, P. I., Kolnes, A. J., & Lai, C. (2011). The Role of Skeletal Muscle Glycogen Breakdown for Regulation of Insulin Sensitivity by Exercise. Frontiers in Physiology, 2. https://doi.org/10.3389/fphys.2011.00112
3. Houten, S. M., Violante, S., Ventura, F. V., & Wanders, J. A. (2016). The Biochemistry and Physiology of Mitochondrial Fatty Acid β-Oxidation and Its Genetic Disorders. https://doi.org/10.1146/annurev-physiol-021115-105045
5. Melzer, K. (2011). Carbohydrate and fat utilization during rest and physical activity. E-SPEN, the European E-Journal of Clinical Nutrition and Metabolism, 6(2), e45-e52. https://doi.org/10.1016/j.eclnm.2011.01.005
6. Tavakoli A, Mirzababaei A, Mirzaei K. Association between low carbohydrate diet (LCD) and sleep quality by mediating role of inflammatory factors in women with overweight and obesity: A cross-sectional study. Food Sci Nutr. 2021 Sep 28;9(11):6252-6261. doi: 10.1002/fsn3.2584. PMID: 34760255; PMCID: PMC8565210.
Marine is a registered dietitian with a passion for well-being, health and metabolism. She started her career as a clinical dietitian, opened her private practice to accompany patients from various backgrounds in their health journey, and is now providing nutrition support for Lumen’s customers.