Belly Fat: A Reality Sandwich? continued...
"That's important, because there is a tendency [in middle-aged people] to gain more weight as they age," Tucker tells WebMD.
But that wasn't the case with those eating roughly the same number of calories each day, but whose carbs included more refined, packaged, and processed foods, or starchy vegetables such as potatoes. Their waistlines expanded three times more (about a half inch per year) compared with the group that ate unrefined and less processed "whole" foods.
Consider the Source
The take-home message, according to a noted obesity expert not involved in Tucker's research: Don't forego carbs altogether, just the bad ones.
"Many people on low-carb diets are making the same kind of mistake seen with low-fat diets in the past, namely, there's the consideration that an entire category of food -- in this case, carbohydrates -- is unhealthy," says David Ludwig, MD, PhD, director of the obesity program at Children's Hospital in Boston." Just as we know there are good fats and unhealthy fats, there are good carbohydrates that are rich in fiber, and less helpful carbohydrates such as white bread, excessive intake of potato products, refined breakfast cereals, and the like."
In fact, Ludwig headed a 1999 study, published in the Journal of the American Medical Association, finding that how much fiber was eaten was a better predictor of weight gain, insulin levels, and other heart disease factors in young adults than how much saturated or other fats were consumed.
Stand by Your Bran
High-fiber foods help control weight in several ways: They tend to fill you up faster, so you're less hungry and less likely to overeat. But they also tend to be lower in their glycemic index, producing less of a spike in blood sugar levels after meals and therefore less of an increase in insulin levels. High glycemic foods -- which include most refined foods and starches -- are associated with more weight gain and greater risk of diabetes.
"It's unclear whether it's the fiber itself, properties associated with fiber such as vitamins, minerals, and phytochemicals, or the fact that people who eat a high-fiber diet have much smaller swings in blood sugar," Ludwig tells WebMD. "But there's little doubt that eating more whole foods rich in fiber is optimal, for controlling weight and good health."