Get to know your carbs: How they fit into a healthy diet

The quality of your carbs matters 

Are you constantly second-guessing your carb intake? If so, you’re not alone. You might be surprised to learn that small changes in the type, timing, and quantity of carbs you consume can significantly impact your health and wellness goals.

Carbohydrates are an essential energy source for the body, fueling everything from daily activities to intense workouts. However, not all carbs are created equal. 

By personalizing the carbs you eat—choosing the right types, consuming them at the optimal times, and in the right amounts—you can unlock their full potential to support your metabolic health. But first, let’s demystify carbohydrates and explore how they work in your body.

What are carbohydrates? 

Carbohydrates are sugar molecules found in many foods. Along with proteins and fats, they are one of the three macronutrients the body needs to function properly. Carbohydrates are fundamental in maintaining our physiology, from powering brain activity to fueling muscle growth. Most importantly, carbs are vital for optimal metabolic function, as your mitochondria, your cells’ powerhouses, use them for energy production in addition to fats [1]. Carbohydrates are essential for maintaining metabolic flexibility—your mitochondria’s ability to seamlessly switch between burning carbs and fats for energy. Improving your metabolic flexibility has several benefits, including weight management, improved energy levels, better sleep, and preventing metabolic syndrome. 

The different types of carbohydrates: Complex vs. simple

While all carbohydrates serve as a fuel source for your mitochondria, the quality of the carbohydrates you consume plays a significant role in how they affect your health and metabolism. Carbohydrates come in many forms, but the two main types are complex and simple. 

Nutrient-dense complex carbohydrates—like whole grains, fruits, and vegetables—help stabilize blood sugar, improve insulin sensitivity, and provide sustained energy [1]. On the other hand, simple carbs—such as refined sugary snacks and white bread—can lead to blood sugar spikes, energy crashes, and long-term metabolic imbalances [1]. 

Complex carbohydrates

Complex carbs are slow-absorbing, which means they take longer to digest. This helps you feel fuller for longer and prevents sharp spikes in blood sugar. Including complex carbohydrates in your diet can provide sustained energy throughout the day and prevent hunger and cravings by stabilizing blood sugar.

Complex carbs provide a steady release of glucose into the bloodstream, helping maintain blood glucose stability, enhance insulin sensitivity, and reduce cravings. High insulin sensitivity means your body needs only a small amount of insulin to help glucose reach your mitochondria and support energy production for daily activities. 

The Journal of Clinical Medicine also notes that fiber-rich diets, often derived from complex carbohydrates, improve blood sugar regulation and reduce the risk of developing type 2 diabetes and other metabolic conditions [2]. 

These are some complex carbs you can include in your diet:

• Whole grains (e.g., brown rice, quinoa, oats)
• Legumes (e.g., lentils, chickpeas, black beans)
• Vegetables (e.g., broccoli, sweet potatoes, squash)
• Fruits (e.g., apples, berries, citrus fruits)
• Nuts and seeds (e.g., almonds, hemp seeds, chia seeds)

Simple carbohydrates

Simple carbs are fast-absorbing and low in fiber, often leading to an instant blood sugar spike. Consuming excessive amounts of simple carbohydrates is linked to obesity and metabolic syndrome [3]. Obesity is a leading risk factor for chronic diseases, including cardiovascular issues, musculoskeletal disorders, and certain cancers.

Excessive consumption of simple carbohydrates is also linked to insulin resistance, type 2 diabetes, and other chronic illnesses [4, 5]. Insulin resistance occurs when insulin cannot efficiently shuttle glucose from the bloodstream to the cells [6]. This impairs energy production, making it harder for your mitochondria to use glucose for energy when you need it.  

Examples of simple carbs:

Sugary snacks (e.g., candy, pastries, cake)

Refined grains (e.g., white bread, white pasta, breakfast cereals)

Sweetened beverages (e.g., soda, fruit juice, energy drinks)

Carbs and metabolism: Additional ways they work together

Let’s explore other ways carbohydrates and metabolism are interconnected.

Carb timing

When you eat carbs can significantly impact how effectively your body processes and uses them. 

Aligning carbohydrate intake with your body’s natural circadian rhythm by eating more carbs in the morning may optimize glucose metabolism and support better overall health. One study examining this link found that insulin secretion and sensitivity peaked in the morning and declined by the evening, suggesting that the body’s ability to manage glucose is more efficient earlier in the day [7].

Because your mitochondria transition from carb burn to fat burn at rest and while sleeping, consuming late dinners and high-carb meals later in the evening can hinder the overnight shift to fat burn, potentially impairing sleep quality. 

Timing carbohydrates around exercise is another effective strategy to boost metabolism. After a workout, you’re more insulin-sensitive, and the carbs you eat can replenish your glycogen, the stored form of glucose in muscles and the liver, and help with recovery and building muscle mass [8].

“The combination of metabolic feedback and daily plans Lumen gives me a structure to work to enabling me to fuel the best for my daily requirements.”

Maria, 52, England

Carb quantity

Eating more carbs than you can store as glycogen forces your body to convert the excess into fat. At the same time, this overworks your mitochondria, causing oxidative stress that damages their membranes. Plus, chronically high glycogen levels can make your mitochondria overly reliant on carbs and reduce their ability to burn fat effectively, hampering weight loss and body recomposition efforts.

A well-planned meal can ensure a balanced ratio of complex carbohydrates, healthy fats, and high-quality protein, preventing over-reliance on carbs for energy. 

Carb cycling

Carb cycling involves alternating between days of low-carb and high-carb eating. Carb cycling pushes the mitochondria to fat burn when low on carbs, while high-carb days allow the body to replenish glycogen. You can sync your carb cycling with your fitness schedule. For high-intensity workouts like weightlifting, you can plan to eat more carbs to support muscle growth and recovery and for low-intensity aerobic workouts and rest days, you can eat low carb.

“Many people believe that adopting a healthy lifestyle means cutting out carbohydrates,” shares Ulrike Kuehl, Head of Nutrition at Lumen. "However, confining ourselves to these carb-restrictive diets for prolonged periods might compromise our metabolic flexibility and prevent us from reaching our health goals.”

How to personalize your carb intake

Measure your metabolism to eliminate guesswork about the amount of carbs you should consume daily and receive recommendations about which carbs to eat and when. A metabolic tracker like Lumen can provide you with a personalized nutrition plan and macros, as well as meal recommendations and metabolic insights based on your real-time results.

If you’re carb cycling, Lumen can help you identify which days to eat low carb versus high carb based on your metabolic measurements. Depending on whether you’re burning carbs or fats for fuel, Lumen provides a nutrition plan for the day with a breakdown of how many carbs, proteins, and fats you should consume to improve your metabolic flexibility.

Optimize your metabolism with complex carbs

High-quality complex carbs are essential for supporting optimal health and well-being. Understanding how to choose the right carbs empowers you to make informed decisions and is a step toward building a more resilient body, weight management, balanced energy levels, and achieving metabolic flexibility. 

With Lumen, you can measure your metabolism and receive tailored lifestyle strategies based on your real-time results to set yourself up for long-term success on your health journey.

Sources

[1] Holesh JE, Aslam S, Martin A. Physiology, Carbohydrates. [Updated 2023 May 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459280/

[2] Hoyas, I., & Leon-Sanz, M. (2019). Nutritional Challenges in Metabolic Syndrome. Journal of clinical medicine, 8(9), 1301. https://doi.org/10.3390/jcm8091301

[3] Ferretti, F., & Mariani, M. (2017). Simple vs. Complex Carbohydrate Dietary Patterns and the Global Overweight and Obesity Pandemic. International journal of environmental research and public health, 14(10), 1174. https://doi.org/10.3390/ijerph14101174

[4] McClenaghan N. H. (2005). Determining the relationship between dietary carbohydrate intake and insulin resistance. Nutrition research reviews, 18(2), 222–240. https://doi.org/10.1079/NRR2005109

[5] Clemente-Suárez, V. J., Mielgo-Ayuso, J., Martín-Rodríguez, A., Ramos-Campo, D. J., Redondo-Flórez, L., & Tornero-Aguilera, J. F. (2022). The Burden of Carbohydrates in Health and Disease. Nutrients, 14(18), 3809. https://doi.org/10.3390/nu14183809

[6] Freeman, A. M. (2023, August 17). Insulin resistance. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK507839/ 

[7] Zhao, L., Hutchison, A., Heilbronn, L. (2021). Carbohydrate intake and circadian synchronicity in the regulation of glucose homeostasis. Current Opinion in Clinical Nutrition and Metabolic Care. DOI:10.1097/MCO.0000000000000756

[8] Kerksick, C. M., Arent, S., Schoenfeld, B. J., Stout, J. R., Campbell, B., Wilborn, C. D., Taylor, L., Kalman, D., Smith-Ryan, A. E., Kreider, R. B., Willoughby, D., Arciero, P. J., VanDusseldorp, T. A., Ormsbee, M. J., Wildman, R., Greenwood, M., Ziegenfuss, T. N., Aragon, A. A., & Antonio, J. (2017). International society of sports nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition, 14, 33. https://doi.org/10.1186/s12970-017-0189-4