The human body can handle carbohydrates from whole foods: roots, tubers, fruits, vegetables, beans, lentils, nuts, seeds, and some grains. But today, many people get most of their carbohydrates from refined flour, sugar, snacks, cereals, breads, pasta, juices, desserts, sweetened drinks, and ultra-processed foods. This is where the metabolic damage begins.
1. How the Body Uses Carbohydrates
When we eat carbohydrates, the digestive system breaks them down mostly into glucose, which enters the bloodstream as blood sugar. Glucose can be used immediately for energy by the brain, muscles, red blood cells, and organs, or stored as glycogen in the liver and muscles for later use. When glycogen stores are full, excess glucose can be converted into fat.
There are three major types of carbohydrates:
Simple carbohydrates: sugar, honey, juice, sweets, and sweetened drinks. They are absorbed quickly and can spike blood sugar.
Starches: bread, rice, pasta, potatoes, corn, and grains. They break down into glucose, but their effect depends on processing, fiber, portion size, and what they are eaten with.
Fiber: technically a carbohydrate, but not digested like sugar. Fiber feeds the microbiome, slows glucose absorption, supports bowel movements, improves satiety, and is associated with better heart and digestive health.
2. Carbs Are Not All the Same
A sweet potato and a donut are both “carbs,” but they behave very differently in the body.
Whole-food carbohydrates come with fiber, minerals, polyphenols, water, and resistant starch. Refined carbohydrates are often stripped of fiber and combined with added sugar, seed oils, additives, and flavor enhancers.
Whole grains, legumes, vegetables, berries, and roots provide a more complete nutrient package. Refined grains and sugars are rapidly digested and can create larger blood sugar fluctuations. Low-glycemic foods like oats, legumes, and intact whole grains digest more slowly and create a more gradual glucose rise.
Functional Medicine Perspective: Carbs Are Not Essential for Life
Dr. Mark Hyman often explains that there is no such thing as an “essential carbohydrate.” In nutrition science, “essential” means the body cannot make it and must get it from food. We have essential amino acids from protein and essential fatty acids from fat, but we do not have essential carbohydrates.
The body can make the glucose it needs through gluconeogenesis and can also use ketones as an alternative fuel source. This means carbohydrates are not required for survival in the same way protein, healthy fats, vitamins, minerals, and water are.
But this does not mean all carbohydrates are bad. It means carbs should be used wisely.
From a functional medicine perspective, carbohydrates are best seen as optional fuel, not the foundation of every meal. For many people with belly fat, cravings, insulin resistance, inflammation, fatigue, perimenopause, menopause, fatty liver, or poor metabolic flexibility, carbs should be more like a strategic tool or an occasional treat.
The best choices are whole-food carbs that come with fiber and nutrients: berries, vegetables, lentils, beans, sweet potatoes, squash, carrots, beets, quinoa, oats, and resistant starches like cooled rice or cooled potatoes.
The carbs to limit are refined and processed: sugar, bread, pasta, pastries, cereal, crackers, chips, juice, sweet coffee drinks, and most gluten-free packaged snacks.
Simple message:
There are essential proteins.
There are essential fats.
But there are no essential carbohydrates.
Carbs are not essential, but if you choose them, choose them wisely.
3. Were Humans Originally Carnivores?
This is where we need nuance.
Humans were not universally “carnivore.” Human diets changed depending on geography, climate, season, and food availability. Some ancestral groups ate more animal foods, especially in colder climates. Others ate more plant foods, including tubers, roots, fruits, seeds, berries, and honey.
Modern hunter-gatherer examples, like the Hadza, eat a seasonal diet that includes meat, tubers, berries, baobab, and honey. Research on hunter-gatherers shows large variation in animal versus plant intake and carbohydrate intake depending on environment.
So, the real story is not “humans were carnivore and then became carb eaters.” A more accurate statement is:
Humans evolved eating whole, seasonal, unprocessed foods — sometimes higher in animal foods, sometimes higher in plant foods — but never modern refined carbohydrates all day long.
4. How Did We Move Toward a High-Carbohydrate Diet?
The biggest shift happened with agriculture, about 10,000–12,000 years ago. Humans began relying more heavily on grains, legumes, and starchy crops. This changed human biology. For example, the AMY1 gene, which helps produce salivary amylase to digest starch, varies across populations. Populations with historically higher-starch diets tend to have more AMY1 copies.
This means the human body did adapt somewhat to starch. But agriculture is not the same as modern ultra-processed food.
Traditional starches were usually eaten as beans, lentils, roots, tubers, fermented grains, minimally processed grains, whole fruits, vegetables, and seasonal foods.
Modern carbohydrates are often white flour, sugar, cereal, crackers, cookies, pasta, pizza, bread, sweet drinks, snack bars, sweetened yogurt, desserts, processed rice products, and packaged foods.
That is a very different metabolic experience.
5. Why Did Carbohydrate Intake Increase So Much?
Carbohydrates became dominant in the modern diet because they are cheap, shelf-stable, profitable, easy to flavor, and easy to overeat.
Refined flour, sugar, corn syrup, and starches are heavily used by the food industry because they create products that are inexpensive, addictive, convenient, and highly palatable. Ultra-processed foods now make up a large portion of the American diet.
The problem is not just carbohydrates themselves. The problem is the combination of refined carbs + added sugar + low fiber + frequent snacking + low protein + low muscle mass.
6. The Health Risks of a High Refined-Carbohydrate Diet
The biggest risk is not eating a bowl of beans or a sweet potato. The risk is chronic exposure to high-glycemic, low-fiber, processed carbohydrates.
Over time, this pattern may contribute to:
Blood sugar dysregulation
Frequent glucose spikes can lead to energy crashes, cravings, hunger, irritability, and eventually insulin resistance in susceptible people.
Insulin resistance and type 2 diabetes
When the body is exposed to too much glucose too often, insulin has to work harder. Over time, cells can become less responsive to insulin.
Abdominal fat and fatty liver
Excess refined carbohydrates and sugars, especially when combined with excess calories, can promote fat storage around the abdomen and liver.
Inflammation
Blood sugar spikes, excess visceral fat, and ultra-processed foods can contribute to inflammatory signaling.
Cardiovascular risk
High refined-carbohydrate diets can worsen triglycerides, HDL, LDL particle patterns, ApoB risk, and blood pressure in some people, especially when combined with low fiber and poor metabolic health.
Poor gut health
Low-fiber diets starve beneficial gut bacteria. The microbiome needs diverse fibers and polyphenols from plants.
Loss of metabolic flexibility
The body becomes less efficient at switching between burning glucose and burning fat.
7. The Problem with Eating 70–80% Carbs
A 70–80% carbohydrate diet is not automatically harmful if it comes from whole, high-fiber, minimally processed foods and the person is highly active, metabolically healthy, and eating enough protein.
But for many modern people, 70–80% carbohydrates often means bread, pasta, rice, cereal, crackers, sweet coffee drinks, desserts, granola bars, chips, juice, alcohol, snacks, and low-protein meals.
That pattern can become dangerous because the body receives glucose all day long, often without enough protein, muscle stimulus, fiber, minerals, or healthy fats to stabilize metabolism.
For women in perimenopause and menopause, this becomes even more important because declining estrogen can make the body more prone to insulin resistance, abdominal fat, muscle loss, sleep changes, and inflammation.
8. How to Be Smarter with Carbohydrates
The goal is not “zero carbs.” The goal is strategic carbs.
1. Choose carbs that come with fiber
Best choices include berries, apples, citrus, sweet potato, squash, carrots, beets, beans, lentils, chickpeas, quinoa, buckwheat, oats, chia, flax, vegetables, and resistant-starch foods like cooled potatoes or cooled rice in small portions.
2. Avoid naked carbs
Do not eat carbohydrates alone. Pair them with:
protein + fiber + healthy fat
Instead of eating rice alone, eat salmon, vegetables, avocado, and a small portion of rice.
Instead of fruit alone, eat berries with Greek-style coconut yogurt, chia, collagen, or protein.
3. Eat protein first
A powerful strategy is:
vegetables first → protein/fat second → carbs last
This can help reduce the glucose spike from the meal.
4. Time carbs around activity
Carbs are better tolerated when the muscles are active. The best time for higher-starch carbs is often after strength training or earlier in the day, not late at night while sedentary.
5. Prioritize protein
Many people overeat carbs because they under-eat protein. Protein improves satiety, preserves muscle, supports metabolism, and reduces cravings.
A good general target for many adults is around 1.2–1.6 g of protein per kg of body weight per day, sometimes higher depending on goals, age, training, and clinical status.
6. Use the carb hierarchy
Best: vegetables, berries, beans, lentils, roots, tubers, and intact whole grains.
Moderate: rice, potatoes, quinoa, oats, sourdough, and gluten-free whole grains.
Limit: bread, pasta, crackers, cereal, granola, and chips.
Avoid most of the time: juice, soda, candy, pastries, sweetened coffee drinks, refined desserts, and ultra-processed snacks.
7. Watch the dose
For many metabolically healthy people, a smart portion is:
½ cup cooked rice, quinoa, or beans
½ medium sweet potato
1 small fruit
1 cup berries
or ¼ plate of starch at a meal.
For insulin resistance, belly fat, diabetes risk, PCOS, fatty liver, or menopause-related weight gain, carbs may need to be more controlled and personalized.
9. Final Message
Carbohydrates are not the enemy. Modern processed carbohydrates are the problem.
Our ancestors did eat carbohydrates, but they ate them from nature: roots, fruits, tubers, plants, seeds, and seasonal foods. Today, many people eat carbohydrates from factories: flour, sugar, syrup, snacks, and ultra-processed foods.
The body can use carbohydrates well when they come with fiber, minerals, movement, muscle, and metabolic health. But when carbohydrates are refined, frequent, and excessive, they can drive blood sugar instability, cravings, belly fat, inflammation, insulin resistance, and accelerated aging.
Be smart with carbs: choose whole-food carbs, pair them with protein, eat fiber first, move your body, build muscle, and avoid eating sugar and refined flour all day long.
Sources / References
- Hyman, Mark. “Food Bites with Dr. Hyman: Carbohydrates.” Dr. Mark Hyman.
https://drhyman.com/blogs/content/food-bites-with-dr-hyman-carbohydrates
Useful for: the functional medicine explanation that there is no such thing as an “essential carbohydrate,” but that smart, low-glycemic plant carbohydrates can still be useful. - StatPearls / NCBI Bookshelf. “Biochemistry, Ketogenesis.” National Library of Medicine.
https://www.ncbi.nlm.nih.gov/books/NBK493179/
Useful for: ketones as an alternative fuel source and gluconeogenesis during low-carbohydrate availability. - StatPearls / NCBI Bookshelf. “Physiology, Glucose Metabolism.” National Library of Medicine.
https://www.ncbi.nlm.nih.gov/books/NBK560599/
Useful for: how glucose is used for energy, glycogen, and metabolic functions in the body. - Harvard T.H. Chan School of Public Health. “Carbohydrates and Blood Sugar.” The Nutrition Source.
https://nutritionsource.hsph.harvard.edu/carbohydrates/carbohydrates-and-blood-sugar/
Useful for: glycemic index, glycemic load, refined carbohydrates, and blood sugar response. - Harvard T.H. Chan School of Public Health. “Whole Grains.” The Nutrition Source.
https://nutritionsource.hsph.harvard.edu/what-should-you-eat/whole-grains/
Useful for: difference between whole grains and refined grains. - Harvard T.H. Chan School of Public Health. “Fiber.” The Nutrition Source.
https://nutritionsource.hsph.harvard.edu/carbohydrates/fiber/
Useful for: fiber, blood sugar control, satiety, digestion, and metabolic health. - CDC / National Center for Health Statistics. “Ultra-processed Food Consumption in Youth and Adults: United States, August 2021–August 2023.” NCHS Data Brief No. 536, August 2025.
https://www.cdc.gov/nchs/products/databriefs/db536.htm
Useful for: data showing ultra-processed foods contribute about 53% of adult calories and 61.9% of youth calories in the U.S. - CDC. “Get the Facts: Added Sugars.”
https://www.cdc.gov/nutrition/php/data-research/added-sugars.html
Useful for: added sugar and its connection to weight gain, obesity, type 2 diabetes, and heart disease. - Dietary Guidelines for Americans. “Cut Down on Added Sugars.”
https://www.dietaryguidelines.gov/sites/default/files/2021-11/DGA_FactSheet_AddedSugars_2021-06_508c.pdf
Useful for: recommendation to limit added sugars to less than 10% of daily calories. - NIDDK. “Insulin Resistance & Prediabetes.” National Institute of Diabetes and Digestive and Kidney Diseases.
https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
Useful for: insulin resistance, blood glucose, prediabetes, and weight gain. - NIDDK. “Risk Factors for Type 2 Diabetes.”
https://www.niddk.nih.gov/health-information/diabetes/overview/risk-factors-type-2-diabetes
Useful for: obesity, inactivity, age, family history, and other diabetes risk factors. - Mann, Neil J. “Dietary Lean Red Meat and Human Evolution.” European Journal of Nutrition, 2000.
https://pubmed.ncbi.nlm.nih.gov/19350623/
Useful for: human ancestral diet variation and the role of animal and plant foods in hunter-gatherer diets. - Perry, George H. et al. “Diet and the Evolution of Human Amylase Gene Copy Number Variation.” Nature Genetics, 2007.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2377015/
Useful for: AMY1 gene adaptation and starch digestion in populations with historically higher-starch diets. - Harvard Health Publishing. “The Facts on Fiber.” Harvard Medical School.
https://www.health.harvard.edu/diet-and-nutrition/the-facts-on-fiber
Useful for: high-fiber diets, LDL cholesterol, cardiovascular disease, diabetes, gut microbiome, and inflammation. - Mayo Clinic. “Prediabetes: Symptoms and Causes.”
https://www.mayoclinic.org/diseases-conditions/prediabetes/symptoms-causes/syc-20355278
Useful for: prediabetes risks, progression to type 2 diabetes, fatty liver, cardiovascular risk, and metabolic complications.