To Avoid Middle-Age Weight Gain, Carb Quality, Not Quantity, May Matter Most
When it comes to maintaining body weight, carbs are often maligned. But a new study suggests you may not need to slash them from your diet if this is your goal — you may just need to reach for high-quality sources.
For the study, which was published September 27, 2023, in BMJ, scientists examined more than two decades’ worth of data consisting of weight changes and eating habits from about 137,000 adults starting when they were 50 years old, on average. Over time, people gained more weight when they ate more refined grains like white bread, starchy vegetables like potatoes, peas, and corn, and sugary drinks including soda. Conversely, participants gained less weight over time when they consumed more whole grains, fruit, and nonstarchy veggies.
“Where we’re getting our calories from matters, in terms of our ability to avoid middle-age weight gain,” says Brooke Aggarwal, EdD, an assistant professor of cardiology at Columbia University Irving Medical Center in New York City, who wasn’t involved in the new study.
“Replacing sugars and refined carbs with carbs such as whole grains, fruits, and nonstarchy vegetables might help to avoid middle-age weight gain, because these foods are good sources of fiber,” Dr. Aggarwal adds.
Carbohydrates found in whole, minimally processed foods are almost always higher in fiber than refined or heavily processed carbohydrates, says Maya Adam, MD, a clinical associate professor at Stanford University School of Medicine in California who wasn’t involved in the new study.
“Dietary fiber has many health benefits, including the fact that it keeps us feeling full for longer, so we often find ourselves eating less when we eat higher-fiber foods,” Dr. Adam says.
Study participants gained an average of 1.5 kilograms (kg) (3.3 pounds [lb]) every four years, and an average of 8.8 kg (19.4 lb) over the entire follow-up period. But the amount of weight they gained depended on the types of carbohydrates they consumed.
For example, every extra 100 grams (g) a day of carbohydrates from whole grains was associated with 0.4 kg (0.9 lb) less weight gain over four years, while every additional 100 g a day of fruit was tied to 1.6 kg (3.5 lb) less weight gain, and each extra 100 g of nonstarchy vegetables was linked to 3 kg (6.6 lb) less weight gain.
By contrast, weight gain increased every four years by 0.8 kg (1.8 lb) for each 100 g daily increase in refined grains, and by 2.6 kg (5.7 lb) for every 100 g daily increase in starchy veggies.
One limitation of the study is that researchers relied on participants to accurately recall and report on what they ate and how much their weight changed over time. That means there was a chance for human error, which could have affected the data. The study also wasn’t designed to prove whether specific shifts in carbohydrate consumption might directly cause changes in weight.
Even so, there are many clear benefits to a diet with more carbohydrates from whole grains, fruits, and nonstarchy veggies, and fewer carbs from sugars and starches, according to the Mayo Clinic. Weight loss is one, but other positive outcomes can include lower blood pressure, lower cholesterol, lower blood sugar, and a reduced risk of type 2 diabetes and a wide range of cardiovascular diseases.
How you prepare fruits and veggies also matters, says Holly Lofton, MD, the director of the medical weight management program at NYU Langone Health in New York City. That’s because when these foods are juiced or pureed, they lose a lot of the fiber content, says Dr. Lofton, who wasn’t involved in the new study. This means an apple is better than applesauce or apple juice.
People who want to make changes but aren’t sure where to start should focus first on what they drink, advises the senior study author Walter Willett, MD, DrPH, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston.
“Regular soda is the worst form of calories,” Dr. Willett says. All, or nearly all, of the calories in regular soda come from sugars. Sodas and other sugar-sweetened beverages like energy drinks are the single biggest source of calories and added sugar in the U.S. diet, according to the Harvard T.H. Chan School of Public Health. Swapping soda for water or unsweetened coffee or tea is the best way to begin. Diet sodas are better than regular soda if it’s impossible to cut this out entirely, but less soda is still better regardless of how it’s sweetened, he adds.
“After soda reduction, shifting from refined grains to whole grains is usually the next best change,” Willett says. This could mean trading white breads and pastas for the whole-grain versions. “Making all these changes will be optimal and will have many other health benefits in addition to weight control,” Willett adds.
