Carbohydrates are often vilified by proponents of fad diets, but a recent study by University associate professor Michael Keenan suggests eating certain kinds of carbohydrates can actually lower body fat.
According to Keenan, beans and whole grains are made of a starch called resistant fiber. Resistant fiber differs from other starches because it resists digestion and accumulates in the large intestine, which serves as a home for many beneficial bacteria. Other starches end up in the small intestine, where they are immediately absorbed and either turned into energy or stored as fat.
Food that travels to the large intestine is typically fermented by bacteria in a way that speeds up metabolism. Resistant starch in particular promotes the growth of these helpful bacteria, so individuals who eat more of this starch experience an increase in metabolism.
Keenan said he believes incorporating more resistant starches in commercial food products could accelerate efforts to fight obesity and Type 2 diabetes.
“A dietician once told me he never met a carb he didn’t like, but the quality of the carbs you consume is generally more important than the quantity,” Keenan said.
In his study, Keenan fed resistant starch corn to half of his lab rats and regular corn to the other half. Many of the rats that ate the resistant starch corn experienced a significant reduction in body fat.
Though Keenan performed most of his experiments on lab rats, he recently conducted a pilot study with humans, but he fed them resistant starch breakfast bars instead of corn. The results were promising.
“Many of the people who ate the starch did see a reduction in body fat,” Keenan said.
Some of the subjects, however, did not experience significant fat loss. Keenan attributed this to insulin resistance. Individuals afflicted with this condition do not respond to the insulin their bodies produce in normal ways. Keenan said this condition is often a precursor to Type 2 diabetes and usually occurs when people eat too many refined sugars and lead sedentary lifestyles.
“You don’t normally find this kind of thing in active people,” Keenan said.
Keenan said taking probiotics and eating resistant starches would probably allow for more beneficial bacteria to grow, even in people with insulin resistance. Currently, probiotics alone do not allow for instant colonization, but Keenan said the next wave of probiotics will be more conducive to long-term bacterial growth.
Keenan’s research has already affected the way some nutrition companies make and market their products. He received $1.6 million to finance the experiments he conducts with Eric Ravussin at the Pennington Biomedical Research Center and Roy Martin of the University of California at Davis. Keenan also received a $94,000 grant from the food company Ingredion, which now sells resistant starches under the brand name Hi-Maize, for his own personal research. Ingredion boasts eating Hi-Maize as an effective weight management strategy, and the product has already been met with commercial success.
In the next phase of Keenan’s research, he will feed resistant starches to people who qualify as prediabetics. If the studies yield positive results, resistant starches will likely be incorporated into both medical and commercial products in the near future, he said.
“Many of the people who ate the starch did see a reduction in body fat.”