Healthy Weight
Study Shows That Eating Certain Types Of Carbs Helps Prevent Weight Gain
Author:Molly Knudsen, M.S., RDNJuly 11, 2026
Registered Dietitian Nutritionist
By Molly Knudsen, M.S., RDN
Image by Cameron Whitman / Stocksy
July 11, 2026
Carbs commonly get a bad rap in the nutrition realm. But not all carbs are created equal (case in point: Eating broccoli is very different from eating potato chips). And the notion that eating carbs automatically leads to unwanted weight gain is just not accurate
Instead, long-term studies show again and again that the quality and type of carb is what tips the scale the most (over the years) toward weight gain or loss.
Most recently, researchers from Harvard recently published a study in BMJthat looked into what carbs are most likely to lead to more weight gain1
How the study was set up
To see the impact of certain types of carbohydrate consumption on weight status in midlife, researchers followed 136,432 healthy people around the age of 50 (84% women) for 24 to 28 years. And about every four years, they collected data about the study participants’ food consumption and weight.
There were five buckets for carbohydrate food
- Carbohydrates from nonstarchy vegetables (including leafy greens, bell peppers, cucumbers, etc.)
- Fiber (from fruits, vegetables, and whole grains)
- Added sugar (from processed foods like sugar-sweetened beverages, candies, etc.)
- Starch (carbohydrates that aren’t fiber or added sugars)
- Carbohydrates from starchy vegetables (including peas, corn, French fries, potato chips, potatoes, and yams)
Information about other lifestyle factors that impact weight (such as smoking status, sleep duration, screen use, etc.) was also collected so it could be accounted for during analysis and not cloud the results of the relationship of interest: carbs and weight status (particularly weight gain).
So what’s the relationship between carbohydrates and weight?
On average over the course of the study, people gained 3.3 pounds every four years. This isn’t necessarily surprising since weight tends to increase with age2 thanks to hormonal shifts or changes in physical activity, sleep, and stress
Researchers analyzed whether eating certain categories of carbs was associated with more or less weight gain than this average. Given the overall healthy status and age of the group of people in the study, weight gain is a risk for future health complications
So in the context of this study, less weight gain is more desirable. And weight loss can actually be dangerous as you get older (that’s why everyone in this study was younger than 65)
Here’s what they found
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The best carbs for weight status
There was a strong correlation between eating morenonstarchy vegetables and less weight gain. Each 100 grams of daily nonstarchy vegetable intake was associated with 6.6 pounds of less weight gain every four years
For reference, 100 grams of nonstarchy veggies looks like this:
- 1 cup of chopped carrots (raw)
- Just over 1 cup of chopped broccoli (raw)
- 1 small red tomato (raw)
- 3.5 cups raw spinach (raw)
These nonstarchy veggies are known for being nutrient-dense—meaning they are loaded with nutrients and not a lot of calories. So adding more of these foods to your diet ups your intake of essential vitamins and minerals and adds bulk and volume to your plate without excess energy.
Eating more fiber also helps prevent excess weight gain—although to a lesser extent. Each 10-gram increase in daily fiber intake was linked to 1.8 pounds less weight gain over four years.
Researchers speculated that fiber’s satiating qualities and positive effects on gut health help regulate food intake and body weight.
The carbs linked to the most weight gain
Results showed a strong connection between eating more added sugars, starchy foods, and starchy vegetables and greater weight gain over every four-year period (2, 3.3, and 5.7 pounds per daily 100-gram intake respectively).
All of these foods also tend to have a higher glycemic index (aka they raise blood sugar levels more quickly) than fibrous foods and nonstarchy veggies, and the researchers also found that people who consumed diets with a higher glycemic load also experienced more weight gain.
So what does this mean for you?
Overall the findings of this study align with current recommendations: Increase your vegetable and fiber intake (including through whole grains), and limit refined carbohydrates and foods full of added sugars (like soda)
On average, most Americans only eat about 16 grams of fiber daily although it’s recommended that women get a minimum of 21 to 25 grams of fiber per day3 and men shoot for a minimum of 30 to 38 grams
So increasing daily fiber count by at least 10 grams is a solid place to start. Incorporate high-fiber foods into each meal and snack. And consider adding a high-quality fiber supplement, like this one (it has 9 grams of soluble, prebiotic fiber per serving!).*
And even minor yearly increases in weight can snowball into more serious health concerns down the road. The best way to combat this is with a holistic lifestyle approach. This includes choosing carbs like nonstarchy veggies and whole grains, as well as prioritizing fiber, protein, and healthy fats. Adding targeted supplements can also be beneficial
Oh, and don’t be scared to eat starchy vegetables
There is one finding from this study we’re concerned is being taken out of context, and that has to do with starchy vegetable intake. Researchers concluded that “Limiting added sugar, sugar-sweetened beverages, refined grains, and starchy vegetables in favor of whole grains, fruit, and nonstarchy vegetables may support efforts to control weight.”
But not all starchy veggies should be demonized or even avoided
Potatoes, peas, and corn are (at their core) nutritious foods. They all offer some fiber and micronutrients like potassium and carotenoids (like beta-carotene and lutein). And they can even be ating.
The kicker here is how they’re processed and consumed. And in this study, it was noted that the majority of this starchy veggie intake came from potatoes.
Past research tells us that most potato consumption in the United Statescomes in the form of French fries, potato chips, or mashed potatoes4 (likely served with other high-calorie foods, like butter, cheese, or sour cream)
So it’s likely safe to infer that the connection between starchy vegetable intake and weight gain in this study is driven most by consumption of processed or fried potatoes.
The takeaway
This study dove into the nitty-gritty of carbohydrate consumption and weight status and likelihood of weight gain. Even eating one to two more servings a day of nonstarchy veggies and bumping up your fiber intake (through food or supplements) can have a significant impact on your weight status over time.
If you are pregnant, breastfeeding, or taking medications, consult with your doctor before starting a supplement routine. It is always optimal to consult with a health care provider when considering what supplements are right for you.
4 Sources
- https://www.bmj.com/content/382/bmj-2022-073939
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4984841/
- https://www.ncbi.nlm.nih.gov/books/NBK56068/table/summarytables.t4/?report=objectonly%5C
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10472713/
