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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) towards weight gain or loss. 

Most recently, researchers from Harvard recently published a study in BMJ that 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 sources:

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.

The best carbs for weight status

There was a strong correlation between eating more non-starchy vegetables and less weight gain. Each 100 grams of daily non-starchy vegetable intake was associated with 6.6 pounds of less weight gain every four years.

For reference, 100 grams of non-starchy veggies looks like:

These non-starchy 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. 

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 non-starchy 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? 

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 mindbodygreen’s organic fiber potency+. This powdered supplement offers six grams of fiber per serving primarily from organic guar beans (which have been shown to help with satiety and maintaining a healthy weight).* 

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 non-starchy veggies and whole grains, as well as prioritizing fiber, protein, and healthy fats. Adding in 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 non-starchy 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 a source of resistant starch if you cook and then cool them before eating. 

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 States comes 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 1-2 more servings a day of non-starchy 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.