The Good, the bad, and the downright confusing about carbs!

Published on UGA's Dietetic Blog, February 21, 2026

Available at: https://www.fcs.uga.edu/fdn/dietetics-blog#the-good-the-bad-and-the-downright-confusing-about-carbs

For years, the debate has raged on the pros and cons of carbohydrates in the diet. Some say they're necessary for your body and the preferred fuel source for the brain. Others blame them for making people gain weight. But what does current science tell us? Researchers have spent decades tracking hundreds of thousands of people to find out what really happens when we eat different types of carbohydrates. What they discovered is much more interesting than simple "carbs are bad" or "carbs are good" messages.

The Type of Carb Matters More Than the Amount

The biggest discovery from recent research is that where your carbs come from may matter much more than how many you eat. A major study published in the British Medical Journal followed 136,432 health professionals for up to 28 years (Wan et al., 2023). The results were eye-opening.

Over 4 years, when people increased their intake by 100 grams of carbohydrate per day from non-starchy vegetables (broccoli, lettuce, peppers) and fruit, they gained 1.6-3 kg less weight. For those who increased their intake by 100 grams of refined grains (white bread, crackers, cookies) and starchy vegetables (potatoes, corn), they gained 0.8-2.6 kg more weight than the fruits and vegetable consumers. The takeaway? The food itself matters more than just counting carbs. Foods rich in natural fiber (a type of carb that takes extra effort to digest) and nutrients affect your body very differently than processed carbs.

Storing Fat May Make You Hungry, Not the Other Way Around

We usually think weight gain works like this: you eat too much, so your body stores the extra calories as fat. Some scientists propose that the opposite might be true. This idea, called the Carbohydrate-Insulin Model (CIM), is detailed in a paper by Ludwig et al (2021).

Here's how the researchers propose it works:

• You eat processed carbs (like white bread, fries, or candy)

• Your body releases lots of insulin, which tells your fat cells to grab and store calories from your blood

• A few hours later, your blood is low on fuel, and your brain and muscles are running on empty

• Your brain notices this and creates intense cravings for quick energy, which means more fast-acting carbs

• While compelling, the CIM cannot establish a causal relationship here and the researchers rightly note that it is difficult to accurately track daily calories outside a controlled environment. Therefore, it may be easier to track what you are eating rather than how much.

Sometimes Science Gets Confusing

Nutrition science is complicated, and studies don't always agree. A large study by Tammi et al (2023) followed over 8,300 Finnish adults for seven years. Results seemed to contradict everything else as the researchers found no connection between total carbs, fiber, or sugar and weight gain.

Before you think this means sugar in excess is fine, the researchers explained why these results might be misleading:

• People lie about food: It's very common for people to misreport what they actually eat in studies

• Good and bad cancel out: When you lump all carbs together, the benefits of good carbs (like vegetables) and the problems from bad carbs (like refined starches) might just cancel each other out in the data

• Different diets: People in Finland may drink fewer sugary sodas than people in other Western countries, which could change the results

  
  

The Bottom Line: Ask a Better Question

The research isn't finished, and future studies in this area are needed. The evidence is building toward one clear message: carbs from whole foods like vegetables, fruits, and minimally processed grains seem to help with weight management. So instead of asking "How many carbs should I eat?" maybe ask yourself: "Where are my carbs coming from?"

When it comes to navigating nutrition messages, recommendations for individuals are specific and vary based on age, medication use, and diagnosed health conditions. Seeking the advice of a registered dietitian nutritionist can help you sift through messages that promote health vs. hype. To find an RDN, use the Find a Nutrition Expert tool at www.eatright.org.

Reviewed by Sloane Stoklosa, UGA Dietetic Intern

References

Ludwig, D. S., Aronne, L. J., Astrup, A., et al (2021). The carbohydrate-insulin model: A physiological perspective on the obesity pandemic. The American Journal of Clinical Nutrition, 114(6), 1873–1885.

Tammi, R., Männistö, S., Harald, K., et al (2023). Different carbohydrate exposures and weight gain—results from a pooled analysis of three population-based studies. International Journal of Obesity, 47(8), 743–749.

Wan, Y., Tobias, D. K., Dennis, K. K., et al (2023). Association between changes in carbohydrate intake and long term weight changes: Prospective cohort study. BMJ, 382.

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