Complex Carbs: The Key to Metabolic Health, Energy & Stable Glucose
Complex carbohydrates can promote healthier blood sugar and more stable energy levels, particularly in people with compromised metabolic function. Eating starchy foods like whole grains, legumes, and green leafy vegetables is typically good due to high-fiber content and low glycemic index.
The Role of Carbohydrates in Energy
Carbohydrates are the primary source of fuel for the human body. (1) These molecules contain carbon, hydrogen, and oxygen atoms. Being one of the three main dietary macronutrients, carbohydrates are mainly used as an energy source, greatly impacting and participating in energy metabolism.
Glucose is effectively used to power movement, cognition, and basic functions. The brain, the muscles, and the organs all rely on glucose to an extent.
When consumed, carbohydrates are broken down into glucose which can be used to create energy in the cell. In addition to providing immediate energy, carbohydrates serve as a critical energy reserve. Excess glucose is stored in liver and muscle tissue as glycogen that can be used later. (2)
The health effects of carbohydrate consumption on the human body greatly depend on meal timing, fiber content, type of carbohydrates, glycemic index, and total glycemic load. These factors heavily determine metabolic function, energy levels, and gut health.
Refined Carbohydrates and Obesity
One of the major drivers of excessive weight gain, metabolic syndrome, and obesity lies in overconsumption of refined carbohydrates. (3) Added sugars and refined carbohydrates seem to strongly impact the epidemics of hypertension and type 2 diabetes. (4)
Simple carbohydrates or high-GI foods tend to spike glucose levels and insulin faster. Such energy lasts for a short duration, transitioning from hyperglycemia (high blood sugar) to hypoglycemia (low blood sugar) fast. Increased glycemic variability negatively affects metabolic function and increases the risk of insulin resistance. (5)
Data shows that independent of central adiposity, diets high in refined carbohydrates and saturated fat are a risk factor for insulin resistance. Beyond that, refined carbs can contribute to low-grade inflammation which is linked to obesity. (6)
While excess glucose availability detrimentally affects metabolic function in muscle, fat, and liver, low-GI and high-fiber diets have shown the potential to offset this, providing metabolic benefits in individuals with metabolic dysfunction. (7)
What are Complex Carbohydrates
Carbohydrates can be broadly categorized into sugars, starches, and fiber. (8) Starting from the simplest form, glucose is a unit of sugar molecule. Starches are made up of many glucose units tied together. Fiber is an even more advanced level, tying multiple sugar units together in a way that cannot be easily broken by digestive enzymes.
Due to the complex structure, the body takes more time to break down complex carbohydrates made up of long chains of sugar molecules. This slows digestion leading to a balanced, gradual increase in energy. In addition, this stabilizes blood sugar levels as glucose is not increased so fast in the blood. (9)
Generally, complex carbohydrate foods tend to pack more nutrients than simple ones. They’re richer in dietary fiber, vitamins, and minerals which support metabolic function, digestion, and gut health.
What are refined carbs?
Refined carbohydrates are processed foods where the fibrous, nutrient-rich parts have been removed, leaving primarily starch or sugar. Examples include white flour, white rice, white bread, pastries, and sugary beverages. These foods digest quickly, causing rapid blood sugar spikes and crashes.
What foods are complex carbs?
Complex carbohydrate foods include whole grains (oats, brown rice, quinoa, barley), legumes (lentils, beans, chickpeas), starchy vegetables (sweet potatoes, squash, corn), non-starchy vegetables (broccoli, leafy greens), and high-fiber fruits (apples, berries, pears).
Is it better to eat complex carbs?
Yes, it’s generally better to eat complex carbs because they
- provide sustained energy without blood sugar spikes
- contain more fiber for digestive health
- include essential vitamins and minerals
- increase satiety and help control appetite
- support healthy gut bacteria
- have been linked to reduced risk of chronic diseases.
What is the difference between simple carbs and complex carbs?
Simple carbs contain one or two sugar molecules, digest quickly, cause rapid blood sugar spikes, and typically lack nutrients (examples: table sugar, honey, fruit juice).
Complex carbs contain longer chains of sugar molecules, digest slowly, release glucose gradually, and typically contain fiber, vitamins and minerals (examples: whole grains, legumes, vegetables).
Simple vs Complex Carbohydrates
As opposed to the slow-digestion properties of complex carbs, simple ones tend to do the opposite. The simpler the carbohydrate, the faster it can be utilized for energy, and the faster it’ll raise blood sugar and insulin levels. Increasing glycemic variability and living in a high-insulin state is detrimental to long-term metabolic health and impairs energy production.
GI or glycemic index determines the speed of blood sugar spike. (10) Lower-GI foods or complex carbohydrates found in legumes, starchy vegetables, whole grains, and high-fiber fruits take longer to process and increase glucose. High-GI foods (candy, bread, cereal, soda, white rice) are simpler ones that tend to put glucose elevation out of control. However, consuming simple carbohydrates is more favorable for athletes or active people who need to derive quick energy to power exercise needs.
Numerous studies show increasing the complexity of carbohydrates consumed to be associated with favorable effects on weight loss, blood sugar control, and metabolic function. Replacing high-GI with low-GI foods is one of the main strategies to enhance glycemic control and reduce metabolic strain on the body. (9) (11)
The Benefits of Complex Carbohydrates
The primary benefits of swapping simple for complex carbohydrates rely on reducing glucose spikes. This shift alone helps regulate energy metabolism in a way that’s not strenuous. Glycemic control is better, insulin isn’t elevated, digestion is slowed down, and satiety is improved.
The exact mechanism that ties keto, fasting, or low-carb diets to improved metabolic health. During such diets, we reduce both the total intake of glucose, reducing the total glycemic load. Additionally, the body has longer glucose depletion phase which improves metabolic markers. (12) (13) (14) (15)
Metabolic Health
The link between increased intake of refined carbohydrates and metabolic syndrome is clear. Simple carbs tend to spike glucose and insulin levels, contributing to metabolic diseases. (3) (5)
Incorporating low-GI and high-fiber foods tend to provide metabolic support, improving metabolic function particularly in obese populations at higher risk for insulin resistance. (11) (7) Some of the most effective strategies in offsetting metabolic dysfunction and obesity-related issues include (9)
- reducing the total amount of carbohydrates (glycemic load)
- consuming more soluble fiber (stable glucose)
- reducing GI by consuming low-GI foods
- having less than 50% energy derived from carbs with breakfast
The general trend is clear. Diets high in simple carbohydrates or high-GI foods tend to exacerbate insulin resistance while fiber-rich and low-GI diets positively interact with glucose and insulin. Indirectly, they can improve body composition and aid in weight loss which further improves metabolic health. (16) (17)
Weight Management
The ability to lose weight is dependent on various factors like metabolic rate, metabolic flexibility, gut microbiota, and energy efficiency. Increased metabolic dysfunction means inefficiency in creating energy with an increased metabolic strain, resulting in inflammation and weight gain.
By introducing complex carbohydrates or reducing the total amount of glucose consumed, individuals are at a state superior for (17) (18) (16)
- creating energy efficiently and sustainably
- reducing glucose and insulin spikes, reducing HOMA-IR
- improving hunger and satiety hormone signaling
- losing weight and burning fat
High-fiber diets are inversely correlated to weight gain, so increasing fiber is an effective strategy for weight loss. Dietary fiber also tends to increase GLP-1 and peptide YY, important satiety signaling hormones. It also contributes to decreased fat consumption in the diet and diet metabolizable energy (what’s left after food digestion). (18)
Gut Health
Electrolytes are mineral salts that help support numerous processes in the body. During extended fasting the metabolism still works to create energy, using up electrolytes. This reduces minerals like potassium, magnesium, chloride, and sodium. (6) which are important in maintaining fluid balance, neural transmission, muscle activation, bone strength, and regulating pH levels. (7)
As the body shifts to fat metabolism and ketone levels increase, the rates of potassium and sodium excretion increase, speeding up electrolyte loss. This can lead to fatigue, headaches, dizziness, and brain fog. Adding electrolytes improves cellular hydration, particularly important during periods of fasting.
Pure, mineral-rich salt that contains the most important trace and macro minerals is one great way to supplement electrolytes. Exclude sugary sport electrolyte powders to not interfere with fasting.
Energy Levels
Unlike simple carbohydrates that cause rapid spikes and crashes in energy, complex ones break down slowly, slowing down digestion and extending energy delivery for longer. This makes energy derived from complex carbs more sustainable and stable, supporting daily performance in both physical and cognitive tasks.
It solves the problem of fatigue most who rely on quick-energy sources like simple carbs experience. Such instability leads to overeating frequently, increasing energy fluctuations while detrimentally affecting hunger and metabolic function.
Glycemic Index
The Glycemic Index (GI) is a measure that ranks foods on how they affect blood sugar levels. Foods with a low GI are digested and absorbed slowly, causing a gradual rise in blood sugar, while foods with a high GI cause a rapid spike in blood sugar. Here’s a breakdown of the GI categories:
- Low GI (55 or less): These foods are slowly digested and absorbed, providing a more stable blood sugar level. They promote satiety and sustained energy.
- Medium GI (56-69): These foods have a moderate effect on blood sugar, causing a moderate rise.
- High GI (70 or more): These foods are rapidly digested, causing a fast increase in blood sugar. They can lead to energy crashes and cravings.
Low, Medium, and High GI Foods
| Food Group | Low GI (55 or less) | Medium GI (56-69) | High GI (70 or more) |
|---|---|---|---|
| Grains | Oats, barley, quinoa, bulgur, brown rice | White rice, couscous, whole wheat bread | White bread, white rice, instant oatmeal |
| Fruits | Apples, pears, cherries, oranges, berries (e.g., strawberries, blueberries, raspberries) | Pineapple, mango, kiwi, peaches | Watermelon, ripe banana, papaya |
| Vegetables | Sweet potatoes, carrots, broccoli, zucchini, spinach, kale, cauliflower, Brussels sprouts | Beetroot, corn, peas | Pumpkin, mashed potatoes, boiled potatoes |
| Legumes | Lentils, chickpeas, kidney beans, black beans, split peas | Pinto beans, navy beans, soybeans | None (all legumes are generally low or medium GI) |
| Nuts and Seeds | Almonds, walnuts, chia seeds, flaxseeds, sunflower seeds | Cashews, peanuts, pistachios | None |
| Dairy | Milk, yogurt (unsweetened) | Low-fat milk, flavored yogurt (unsweetened) | Ice cream, sweetened yogurt |
| Beverages | Herbal tea, unsweetened coffee | Orange juice (fresh, without added sugar) | Soft drinks, fruit juices with added sugar |
Low-GI Food List
Here’s an expanded list of low-GI, high-fiber foods to further diversify your diet for sustained energy and long-term health:
- Whole Grains: Oats, quinoa, barley, bulgur, brown rice, farro, spelt, and amaranth.
- Legumes: Lentils, chickpeas, black beans, kidney beans, split peas, navy beans, pinto beans, and edamame.
- Vegetables: Sweet potatoes, carrots, broccoli, zucchini, spinach, kale, cauliflower, Brussels sprouts, and butternut squash.
- Fruits: Apples, pears, oranges, berries (blueberries, strawberries, raspberries, blackberries), cherries, peaches, plums, apricots, and kiwi.
- Nuts and Seeds: Almonds, walnuts, chia seeds, flaxseeds, sunflower seeds, pumpkin seeds, hemp seeds, and pecans.
- Fiber-Rich Foods: Avocados, artichokes, beets, peas, and mushrooms.
Pairing these foods with lean proteins (like chicken, turkey, tofu, or fish) and healthy fats (like olive oil, avocado, or coconut oil) will provide the necessary balance for optimizing energy levels and overall health. The addition of complex carbs, especially those with a high fiber content, can help manage blood sugar and improve digestive health, supporting energy levels.
Common Myths About Carbohydrates
Here are five common myths about carbohydrates:
Carbs Make You Gain Weight
Carbohydrates on their own do not cause weight gain; they’re an essential piece to energy production. It’s refined carbohydrates and caloric surplus that impair metabolism, resulting in high-insulin states that contribute to fatigue and overeating.
Simple Carbs are Bad for Everyone
Simple carbs provide a quick-energy source which most active people and athletes use up during exercises. In fact, simple carbohydrates are more effective at sustaining energy needs during intense activities. If they’re used properly and timely, carbs fuel exercise without disrupting metabolic health, resulting in high insulin or even weight gain. They provide the muscle with fuel for exercise, improving athletic performance.
Low-Carb Diets are for Everyone
Cutting carbs is not the only, or best way to lose weight for everyone. Very low-carb restrictive diets can impair gut health by not providing enough fiber. Cutting carbs severely can cause a drop in metabolic rate, hypothyroidism, hypoglycemia, and fatigue which, for some, is a great stressor. Reducing carbohydrates needs to be aligned with one’s lifestyle, including work, exercise, and energy needs.
All Carbs Are the Same
There’s a significant difference between refined carbs (like white bread, sugary snacks, and soda) and whole carbs (like fruits, vegetables, and whole grains). Refined carbs are quickly digested and can cause blood sugar spikes, while whole carbs provide essential fiber, vitamins, and minerals and are digested more slowly, promoting stable energy levels and better overall health.
Carbs Should Be Avoided After a Certain Time of Day
Eating anything before bed is not a good idea. The body needs at least three hours to process the food before one falls asleep. It’s no different with carbohydrates, particularly refined sugars. If metabolic function and stable glucose levels are priority, it may be an effective strategy to time starches (carbs) closer to one’s workout window when the muscle is hungry for glucose.
How to Incorporate Complex Carbohydrates
Incorporating more complex carbohydrates is as easy as adjusting your diet to swap the simple for complex carbohydrates. This starts in the grocery store, when one chooses to buy whole-grain pasta, legumes, and quinoa instead of french fries, white bread, and chocolate cake.
Swap Simple for Complex Carbohydrates
Replace refined, simple carbs (like white bread, pastries, and sugary snacks) with nutrient-dense, complex carbohydrates. Examples include whole grains like quinoa, brown rice, oats, and barley, as well as starchy vegetables like sweet potatoes and squash.
Include Low-GI Fruits as Dessert
Instead of sugary desserts, opt for low-GI fruits such as apples, pears, berries, and oranges. These fruits not only satisfy your sweet tooth but also help maintain stable blood sugar levels and provide fiber, antioxidants, and essential nutrients.
Fiber-Rich Breakfast
Start your day with a fiber-rich breakfast to keep you full longer and stabilize blood sugar levels. Choose oatmeal, chia pudding, or a smoothie with fruits like berries, flaxseeds, and spinach.
Fill Your Plate with Vegetables
Make vegetables the focal point of your meals. Include a variety of fiber-rich, complex carb vegetables like sweet potatoes, carrots, broccoli, spinach, and kale.
Incorporate Legumes and Beans
Add legumes such as lentils, chickpeas, black beans, and kidney beans to salads, soups, or stews. Legume-based products like pasta made from chickpeas or lentils are also excellent alternatives to traditional pasta.
Make the Switch to Whole-Wheat
Switch to whole-wheat versions of your favorite bread, pasta, pizza crust, and baked goods. Whole wheat is a great source of complex carbohydrates and fiber, providing longer-lasting energy.
By incorporating these simple strategies, you can enhance your diet with complex carbs that support long-term health, boost energy, and promote stable blood sugar levels throughout the day.
